mirror of https://gitee.com/openkylin/linux.git
112 Commits
| Author | SHA1 | Message | Date |
|---|---|---|---|
David Howells
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9c04caa81b |
FS-Cache: Fix signal handling during waits
wait_on_bit() with TASK_INTERRUPTIBLE returns 1 rather than a negative error code, so change what we check for. This means that the signal handling in fscache_wait_for_retrieval_activation() should now work properly. Without this, the following bug can be seen if CTRL-C is pressed during fscache read operation: FS-Cache: Assertion failed 2 == 3 is false ------------[ cut here ]------------ kernel BUG at fs/fscache/page.c:347! invalid opcode: 0000 [#1] SMP Modules linked in: cachefiles(F) nfsv4(F) nfsv3(F) nfsv2(F) nfs(F) fscache(F) auth_rpcgss(F) nfs_acl(F) lockd(F) sunrpc(F) CPU 1 Pid: 15006, comm: slurp-q Tainted: GF 3.7.0-rc8-fsdevel+ #411 /DG965RY RIP: 0010:[<ffffffffa007fcb4>] [<ffffffffa007fcb4>] fscache_wait_for_retrieval_activation+0x167/0x177 [fscache] RSP: 0018:ffff88002a4c39a8 EFLAGS: 00010292 RAX: 000000000000001a RBX: ffff88002d3dc158 RCX: 0000000000008685 RDX: ffffffff8102ccd6 RSI: 0000000000000001 RDI: ffffffff8102d1d6 RBP: ffff88002a4c39c8 R08: 0000000000000002 R09: 0000000000000000 R10: ffffffff8163afa0 R11: ffff88003bd11900 R12: ffffffffa00868c8 R13: ffff880028306458 R14: ffff88002d3dc1b0 R15: ffff88001372e538 FS: 00007f17426a0700(0000) GS:ffff88003bd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 00007f1742494a44 CR3: 0000000031bd7000 CR4: 00000000000007e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process slurp-q (pid: 15006, threadinfo ffff88002a4c2000, task ffff880023de3040) Stack: ffff88002d3dc158 ffff88001372e538 ffff88002a4c3ab4 ffff8800283064e0 ffff88002a4c3a38 ffffffffa0080f6d 0000000000000000 ffff880023de3040 ffff88002a4c3ac8 ffffffff810ac8ae ffff880028306458 ffff88002a4c3bc8 Call Trace: [<ffffffffa0080f6d>] __fscache_read_or_alloc_pages+0x24f/0x4bc [fscache] [<ffffffff810ac8ae>] ? __alloc_pages_nodemask+0x195/0x75c [<ffffffffa00aab0f>] __nfs_readpages_from_fscache+0x86/0x13d [nfs] [<ffffffffa00a5fe0>] nfs_readpages+0x186/0x1bd [nfs] [<ffffffff810d23c8>] ? alloc_pages_current+0xc7/0xe4 [<ffffffff810a68b5>] ? __page_cache_alloc+0x84/0x91 [<ffffffff810af912>] ? __do_page_cache_readahead+0xa6/0x2e0 [<ffffffff810afaa3>] __do_page_cache_readahead+0x237/0x2e0 [<ffffffff810af912>] ? __do_page_cache_readahead+0xa6/0x2e0 [<ffffffff810afe3e>] ra_submit+0x1c/0x20 [<ffffffff810b019b>] ondemand_readahead+0x359/0x382 [<ffffffff810b0279>] page_cache_sync_readahead+0x38/0x3a [<ffffffff810a77b5>] generic_file_aio_read+0x26b/0x637 [<ffffffffa00f1852>] ? nfs_mark_delegation_referenced+0xb/0xb [nfsv4] [<ffffffffa009cc85>] nfs_file_read+0xaa/0xcf [nfs] [<ffffffff810db5b3>] do_sync_read+0x91/0xd1 [<ffffffff810dbb8b>] vfs_read+0x9b/0x144 [<ffffffff810dbc78>] sys_read+0x44/0x75 [<ffffffff81422892>] system_call_fastpath+0x16/0x1b Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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969695215f |
FS-Cache: Add transition to handle invalidate immediately after lookup
Add a missing transition to the FS-Cache object state machine to handle an invalidation event occuring between the back end completing the object lookup by calling fscache_obtained_object() (which moves to state OBJECT_AVAILABLE) and the backend returning to fscache_lookup_object() and thence to fscache_object_state_machine() which then does a goto lookup_transit to handle the transition - but lookup_transit doesn't handle EV_INVALIDATE. Without this, the following BUG can be logged: FS-Cache: Unsupported event 2 [5/f7] in state OBJECT_AVAILABLE ------------[ cut here ]------------ kernel BUG at fs/fscache/object.c:357! Where event 2 is EV_INVALIDATE. Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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8c209ce721 |
NFS: nfs_migrate_page() does not wait for FS-Cache to finish with a page
nfs_migrate_page() does not wait for FS-Cache to finish with a page, probably leading to the following bad-page-state: BUG: Bad page state in process python-bin pfn:17d39b page:ffffea00053649e8 flags:004000000000100c count:0 mapcount:0 mapping:(null) index:38686 (Tainted: G B ---------------- ) Pid: 31053, comm: python-bin Tainted: G B ---------------- 2.6.32-71.24.1.el6.x86_64 #1 Call Trace: [<ffffffff8111bfe7>] bad_page+0x107/0x160 [<ffffffff8111ee69>] free_hot_cold_page+0x1c9/0x220 [<ffffffff8111ef19>] __pagevec_free+0x59/0xb0 [<ffffffff8104b988>] ? flush_tlb_others_ipi+0x128/0x130 [<ffffffff8112230c>] release_pages+0x21c/0x250 [<ffffffff8115b92a>] ? remove_migration_pte+0x28a/0x2b0 [<ffffffff8115f3f8>] ? mem_cgroup_get_reclaim_stat_from_page+0x18/0x70 [<ffffffff81122687>] ____pagevec_lru_add+0x167/0x180 [<ffffffff811226f8>] __lru_cache_add+0x58/0x70 [<ffffffff81122731>] lru_cache_add_lru+0x21/0x40 [<ffffffff81123f49>] putback_lru_page+0x69/0x100 [<ffffffff8115c0bd>] migrate_pages+0x13d/0x5d0 [<ffffffff81122687>] ? ____pagevec_lru_add+0x167/0x180 [<ffffffff81152ab0>] ? compaction_alloc+0x0/0x370 [<ffffffff8115255c>] compact_zone+0x4cc/0x600 [<ffffffff8111cfac>] ? get_page_from_freelist+0x15c/0x820 [<ffffffff810672f4>] ? check_preempt_wakeup+0x1c4/0x3c0 [<ffffffff8115290e>] compact_zone_order+0x7e/0xb0 [<ffffffff81152a49>] try_to_compact_pages+0x109/0x170 [<ffffffff8111e94d>] __alloc_pages_nodemask+0x5ed/0x850 [<ffffffff814c9136>] ? thread_return+0x4e/0x778 [<ffffffff81150d43>] alloc_pages_vma+0x93/0x150 [<ffffffff81167ea5>] do_huge_pmd_anonymous_page+0x135/0x340 [<ffffffff814cb6f6>] ? rwsem_down_read_failed+0x26/0x30 [<ffffffff81136755>] handle_mm_fault+0x245/0x2b0 [<ffffffff814ce383>] do_page_fault+0x123/0x3a0 [<ffffffff814cbdf5>] page_fault+0x25/0x30 nfs_migrate_page() calls nfs_fscache_release_page() which doesn't actually wait - even if __GFP_WAIT is set. The reason that doesn't wait is that fscache_maybe_release_page() might deadlock the allocator as the work threads writing to the cache may all end up sleeping on memory allocation. However, I wonder if that is actually a problem. There are a number of things I can do to deal with this: (1) Make nfs_migrate_page() wait. (2) Make fscache_maybe_release_page() honour the __GFP_WAIT flag. (3) Set a timeout around the wait. (4) Make nfs_migrate_page() return an error if the page is still busy. For the moment, I'll select (2) and (4). Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Jeff Layton <jlayton@redhat.com> |
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David Howells
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8d76349d35 |
FS-Cache: Exclusive op submission can BUG if there's been an I/O error
The function to submit an exclusive op (fscache_submit_exclusive_op()) can BUG if there's been an I/O error because it may see the parent cache object in an unexpected state. It should only BUG if there hasn't been an I/O error. In this case the problem was produced by remounting the cache partition to be R/O. The EROFS state was detected and the cache was aborted, but not everything handled the aborting correctly. SysRq : Emergency Remount R/O EXT4-fs (sda6): re-mounted. Opts: (null) Emergency Remount complete CacheFiles: I/O Error: Failed to update xattr with error -30 FS-Cache: Cache cachefiles stopped due to I/O error ------------[ cut here ]------------ kernel BUG at fs/fscache/operation.c:128! invalid opcode: 0000 [#1] SMP CPU 0 Modules linked in: cachefiles nfs fscache auth_rpcgss nfs_acl lockd sunrpc Pid: 6612, comm: kworker/u:2 Not tainted 3.1.0-rc8-fsdevel+ #1093 /DG965RY RIP: 0010:[<ffffffffa00739c0>] [<ffffffffa00739c0>] fscache_submit_exclusive_op+0x2ad/0x2c2 [fscache] RSP: 0018:ffff880000853d40 EFLAGS: 00010206 RAX: ffff880038ac72a8 RBX: ffff8800181f2260 RCX: ffffffff81f2b2b0 RDX: 0000000000000001 RSI: ffffffff8179a478 RDI: ffff8800181f2280 RBP: ffff880000853d60 R08: 0000000000000002 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: ffff880038ac7268 R13: ffff8800181f2280 R14: ffff88003a359190 R15: 000000010122b162 FS: 0000000000000000(0000) GS:ffff88003bc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 00000034cc4a77f0 CR3: 0000000010e96000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process kworker/u:2 (pid: 6612, threadinfo ffff880000852000, task ffff880014c3c040) Stack: ffff8800181f2260 ffff8800181f2310 ffff880038ac7268 ffff8800181f2260 ffff880000853dc0 ffffffffa0072375 ffff880037ecfe00 ffff88003a359198 ffff880000853dc0 0000000000000246 0000000000000000 ffff88000a91d308 Call Trace: [<ffffffffa0072375>] fscache_object_work_func+0x792/0xe65 [fscache] [<ffffffff81047e44>] process_one_work+0x1eb/0x37f [<ffffffff81047de6>] ? process_one_work+0x18d/0x37f [<ffffffffa0071be3>] ? fscache_enqueue_dependents+0xd8/0xd8 [fscache] [<ffffffff810482e4>] worker_thread+0x15a/0x21a [<ffffffff8104818a>] ? rescuer_thread+0x188/0x188 [<ffffffff8104bf96>] kthread+0x7f/0x87 [<ffffffff813ad6f4>] kernel_thread_helper+0x4/0x10 [<ffffffff81026b98>] ? finish_task_switch+0x45/0xc0 [<ffffffff813abd1d>] ? retint_restore_args+0xe/0xe [<ffffffff8104bf17>] ? __init_kthread_worker+0x53/0x53 [<ffffffff813ad6f0>] ? gs_change+0xb/0xb Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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75bc411388 |
FS-Cache: Limit the number of I/O error reports for a cache
Limit the number of I/O error reports for a cache to 1 to prevent massive amounts of noise. After the first I/O error the cache is taken off line automatically, so must be restarted to resume caching. Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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c2d35bfe4b |
FS-Cache: Don't mask off the object event mask when printing it
Don't mask off the object event mask when printing it. That way it can be seen if threre are bits set that shouldn't be. Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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03acc4be5e |
FS-Cache: Initialise the object event mask with the calculated mask
Initialise the object event mask with the calculated mask rather than unmasking undefined events also. Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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b4cf1e08c8 |
CacheFiles: Add missing retrieval completions
CacheFiles is missing some calls to fscache_retrieval_complete() in the error handling/collision paths of its reader functions. This can be seen by the following assertion tripping in fscache_put_operation() whereby the operation being destroyed is still in the in-progress state and has not been cancelled or completed: FS-Cache: Assertion failed 3 == 5 is false ------------[ cut here ]------------ kernel BUG at fs/fscache/operation.c:408! invalid opcode: 0000 [#1] SMP CPU 2 Modules linked in: xfs ioatdma dca loop joydev evdev psmouse dcdbas pcspkr serio_raw i5000_edac edac_core i5k_amb shpchp pci_hotplug sg sr_mod] Pid: 8062, comm: httpd Not tainted 3.1.0-rc8 #1 Dell Inc. PowerEdge 1950/0DT097 RIP: 0010:[<ffffffff81197b24>] [<ffffffff81197b24>] fscache_put_operation+0x304/0x330 RSP: 0018:ffff880062f739d8 EFLAGS: 00010296 RAX: 0000000000000025 RBX: ffff8800c5122e84 RCX: ffffffff81ddf040 RDX: 00000000ffffffff RSI: 0000000000000082 RDI: ffffffff81ddef30 RBP: ffff880062f739f8 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000003 R12: ffff8800c5122e40 R13: ffff880037a2cd20 R14: ffff880087c7a058 R15: ffff880087c7a000 FS: 00007f63dcf636e0(0000) GS:ffff88022fc80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f0c0a91f000 CR3: 0000000062ec2000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process httpd (pid: 8062, threadinfo ffff880062f72000, task ffff880087e58000) Stack: ffff880062f73bf8 0000000000000000 ffff880062f73bf8 ffff880037a2cd20 ffff880062f73a68 ffffffff8119aa7e ffff88006540e000 ffff880062f73ad4 ffff88008e9a4308 ffff880037a2cd20 ffff880062f73a48 ffff8800c5122e40 Call Trace: [<ffffffff8119aa7e>] __fscache_read_or_alloc_pages+0x1fe/0x530 [<ffffffff81250780>] __nfs_readpages_from_fscache+0x70/0x1c0 [<ffffffff8123142a>] nfs_readpages+0xca/0x1e0 [<ffffffff815f3c06>] ? rpc_do_put_task+0x36/0x50 [<ffffffff8122755b>] ? alloc_nfs_open_context+0x4b/0x110 [<ffffffff815ecd1a>] ? rpc_call_sync+0x5a/0x70 [<ffffffff810e7e9a>] __do_page_cache_readahead+0x1ca/0x270 [<ffffffff810e7f61>] ra_submit+0x21/0x30 [<ffffffff810e818d>] ondemand_readahead+0x11d/0x250 [<ffffffff810e83b6>] page_cache_sync_readahead+0x36/0x60 [<ffffffff810dffa4>] generic_file_aio_read+0x454/0x770 [<ffffffff81224ce1>] nfs_file_read+0xe1/0x130 [<ffffffff81121bd9>] do_sync_read+0xd9/0x120 [<ffffffff8114088f>] ? mntput+0x1f/0x40 [<ffffffff811238cb>] ? fput+0x1cb/0x260 [<ffffffff81122938>] vfs_read+0xc8/0x180 [<ffffffff81122af5>] sys_read+0x55/0x90 Reported-by: Mark Moseley <moseleymark@gmail.com> Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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ef778e7ae6 |
FS-Cache: Provide proper invalidation
Provide a proper invalidation method rather than relying on the netfs retiring the cookie it has and getting a new one. The problem with this is that isn't easy for the netfs to make sure that it has completed/cancelled all its outstanding storage and retrieval operations on the cookie it is retiring. Instead, have the cache provide an invalidation method that will cancel or wait for all currently outstanding operations before invalidating the cache, and will cause new operations to queue up behind that. Whilst invalidation is in progress, some requests will be rejected until the cache can stack a barrier on the operation queue to cause new operations to be deferred behind it. Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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9f10523f89 |
FS-Cache: Fix operation state management and accounting
Fix the state management of internal fscache operations and the accounting of
what operations are in what states.
This is done by:
(1) Give struct fscache_operation a enum variable that directly represents the
state it's currently in, rather than spreading this knowledge over a bunch
of flags, who's processing the operation at the moment and whether it is
queued or not.
This makes it easier to write assertions to check the state at various
points and to prevent invalid state transitions.
(2) Add an 'operation complete' state and supply a function to indicate the
completion of an operation (fscache_op_complete()) and make things call
it. The final call to fscache_put_operation() can then check that an op
in the appropriate state (complete or cancelled).
(3) Adjust the use of object->n_ops, ->n_in_progress, ->n_exclusive to better
govern the state of an object:
(a) The ->n_ops is now the number of extant operations on the object
and is now decremented by fscache_put_operation() only.
(b) The ->n_in_progress is simply the number of objects that have been
taken off of the object's pending queue for the purposes of being
run. This is decremented by fscache_op_complete() only.
(c) The ->n_exclusive is the number of exclusive ops that have been
submitted and queued or are in progress. It is decremented by
fscache_op_complete() and by fscache_cancel_op().
fscache_put_operation() and fscache_operation_gc() now no longer try to
clean up ->n_exclusive and ->n_in_progress. That was leading to double
decrements against fscache_cancel_op().
fscache_cancel_op() now no longer decrements ->n_ops. That was leading to
double decrements against fscache_put_operation().
fscache_submit_exclusive_op() now decides whether it has to queue an op
based on ->n_in_progress being > 0 rather than ->n_ops > 0 as the latter
will persist in being true even after all preceding operations have been
cancelled or completed. Furthermore, if an object is active and there are
runnable ops against it, there must be at least one op running.
(4) Add a remaining-pages counter (n_pages) to struct fscache_retrieval and
provide a function to record completion of the pages as they complete.
When n_pages reaches 0, the operation is deemed to be complete and
fscache_op_complete() is called.
Add calls to fscache_retrieval_complete() anywhere we've finished with a
page we've been given to read or allocate for. This includes places where
we just return pages to the netfs for reading from the server and where
accessing the cache fails and we discard the proposed netfs page.
The bugs in the unfixed state management manifest themselves as oopses like the
following where the operation completion gets out of sync with return of the
cookie by the netfs. This is possible because the cache unlocks and returns
all the netfs pages before recording its completion - which means that there's
nothing to stop the netfs discarding them and returning the cookie.
FS-Cache: Cookie 'NFS.fh' still has outstanding reads
------------[ cut here ]------------
kernel BUG at fs/fscache/cookie.c:519!
invalid opcode: 0000 [#1] SMP
CPU 1
Modules linked in: cachefiles nfs fscache auth_rpcgss nfs_acl lockd sunrpc
Pid: 400, comm: kswapd0 Not tainted 3.1.0-rc7-fsdevel+ #1090 /DG965RY
RIP: 0010:[<ffffffffa007050a>] [<ffffffffa007050a>] __fscache_relinquish_cookie+0x170/0x343 [fscache]
RSP: 0018:ffff8800368cfb00 EFLAGS: 00010282
RAX: 000000000000003c RBX: ffff880023cc8790 RCX: 0000000000000000
RDX: 0000000000002f2e RSI: 0000000000000001 RDI: ffffffff813ab86c
RBP: ffff8800368cfb50 R08: 0000000000000002 R09: 0000000000000000
R10: ffff88003a1b7890 R11: ffff88001df6e488 R12: ffff880023d8ed98
R13: ffff880023cc8798 R14: 0000000000000004 R15: ffff88003b8bf370
FS: 0000000000000000(0000) GS:ffff88003bd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00000000008ba008 CR3: 0000000023d93000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process kswapd0 (pid: 400, threadinfo ffff8800368ce000, task ffff88003b8bf040)
Stack:
ffff88003b8bf040 ffff88001df6e528 ffff88001df6e528 ffffffffa00b46b0
ffff88003b8bf040 ffff88001df6e488 ffff88001df6e620 ffffffffa00b46b0
ffff88001ebd04c8 0000000000000004 ffff8800368cfb70 ffffffffa00b2c91
Call Trace:
[<ffffffffa00b2c91>] nfs_fscache_release_inode_cookie+0x3b/0x47 [nfs]
[<ffffffffa008f25f>] nfs_clear_inode+0x3c/0x41 [nfs]
[<ffffffffa0090df1>] nfs4_evict_inode+0x2f/0x33 [nfs]
[<ffffffff810d8d47>] evict+0xa1/0x15c
[<ffffffff810d8e2e>] dispose_list+0x2c/0x38
[<ffffffff810d9ebd>] prune_icache_sb+0x28c/0x29b
[<ffffffff810c56b7>] prune_super+0xd5/0x140
[<ffffffff8109b615>] shrink_slab+0x102/0x1ab
[<ffffffff8109d690>] balance_pgdat+0x2f2/0x595
[<ffffffff8103e009>] ? process_timeout+0xb/0xb
[<ffffffff8109dba3>] kswapd+0x270/0x289
[<ffffffff8104c5ea>] ? __init_waitqueue_head+0x46/0x46
[<ffffffff8109d933>] ? balance_pgdat+0x595/0x595
[<ffffffff8104bf7a>] kthread+0x7f/0x87
[<ffffffff813ad6b4>] kernel_thread_helper+0x4/0x10
[<ffffffff81026b98>] ? finish_task_switch+0x45/0xc0
[<ffffffff813abcdd>] ? retint_restore_args+0xe/0xe
[<ffffffff8104befb>] ? __init_kthread_worker+0x53/0x53
[<ffffffff813ad6b0>] ? gs_change+0xb/0xb
Signed-off-by: David Howells <dhowells@redhat.com>
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David Howells
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ef46ed888e |
FS-Cache: Make cookie relinquishment wait for outstanding reads
Make fscache_relinquish_cookie() log a warning and wait if there are any outstanding reads left on the cookie it was given. Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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0f972b5696 |
FS-Cache: Check that there are no read ops when cookie relinquished
Check that the netfs isn't trying to relinquish a cookie that still has read operations in progress upon it. If there are, then give log a warning and BUG. Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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5f4f9f4af1 |
CacheFiles: Downgrade the requirements passed to the allocator
Downgrade the requirements passed to the allocator in the gfp flags parameter. FS-Cache/CacheFiles can handle OOM conditions simply by aborting the attempt to store an object or a page in the cache. Signed-off-by: David Howells <dhowells@redhat.com> |
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David Howells
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c4d6d8dbf3 |
CacheFiles: Fix the marking of cached pages
Under some circumstances CacheFiles defers the marking of pages with PG_fscache
so that it can take advantage of pagevecs to reduce the number of calls to
fscache_mark_pages_cached() and the netfs's hook to keep track of this.
There are, however, two problems with this:
(1) It can lead to the PG_fscache mark being applied _after_ the page is set
PG_uptodate and unlocked (by the call to fscache_end_io()).
(2) CacheFiles's ref on the page is dropped immediately following
fscache_end_io() - and so may not still be held when the mark is applied.
This can lead to the page being passed back to the allocator before the
mark is applied.
Fix this by, where appropriate, marking the page before calling
fscache_end_io() and releasing the page. This means that we can't take
advantage of pagevecs and have to make a separate call for each page to the
marking routines.
The symptoms of this are Bad Page state errors cropping up under memory
pressure, for example:
BUG: Bad page state in process tar pfn:002da
page:ffffea0000009fb0 count:0 mapcount:0 mapping: (null) index:0x1447
page flags: 0x1000(private_2)
Pid: 4574, comm: tar Tainted: G W 3.1.0-rc4-fsdevel+ #1064
Call Trace:
[<ffffffff8109583c>] ? dump_page+0xb9/0xbe
[<ffffffff81095916>] bad_page+0xd5/0xea
[<ffffffff81095d82>] get_page_from_freelist+0x35b/0x46a
[<ffffffff810961f3>] __alloc_pages_nodemask+0x362/0x662
[<ffffffff810989da>] __do_page_cache_readahead+0x13a/0x267
[<ffffffff81098942>] ? __do_page_cache_readahead+0xa2/0x267
[<ffffffff81098d7b>] ra_submit+0x1c/0x20
[<ffffffff8109900a>] ondemand_readahead+0x28b/0x29a
[<ffffffff81098ee2>] ? ondemand_readahead+0x163/0x29a
[<ffffffff810990ce>] page_cache_sync_readahead+0x38/0x3a
[<ffffffff81091d8a>] generic_file_aio_read+0x2ab/0x67e
[<ffffffffa008cfbe>] nfs_file_read+0xa4/0xc9 [nfs]
[<ffffffff810c22c4>] do_sync_read+0xba/0xfa
[<ffffffff81177a47>] ? security_file_permission+0x7b/0x84
[<ffffffff810c25dd>] ? rw_verify_area+0xab/0xc8
[<ffffffff810c29a4>] vfs_read+0xaa/0x13a
[<ffffffff810c2a79>] sys_read+0x45/0x6c
[<ffffffff813ac37b>] system_call_fastpath+0x16/0x1b
As can be seen, PG_private_2 (== PG_fscache) is set in the page flags.
Instrumenting fscache_mark_pages_cached() to verify whether page->mapping was
set appropriately showed that sometimes it wasn't. This led to the discovery
that sometimes the page has apparently been reclaimed by the time the marker
got to see it.
Reported-by: M. Stevens <m@tippett.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
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|
|
Jan Beulich
|
b307d4655a |
FS-Cache: Fix __fscache_uncache_all_inode_pages()'s outer loop
The compiler, at least for ix86 and m68k, validly warns that the comparison: next <= (loff_t)-1 is always true (and it's always true also for x86-64 and probably all other arches - as long as pgoff_t isn't wider than loff_t). The intention appears to be to avoid wrapping of "next", so rather than eliminating the pointless comparison, fix the loop to indeed get exited when "next" would otherwise wrap. On m68k the following warning is observed: fs/fscache/page.c: In function '__fscache_uncache_all_inode_pages': fs/fscache/page.c:979: warning: comparison is always false due to limited range of data type Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Reported-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: David Howells <dhowells@redhat.com> Cc: Suresh Jayaraman <sjayaraman@suse.de> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
|
|
David Howells
|
c902ce1bfb |
FS-Cache: Add a helper to bulk uncache pages on an inode
Add an FS-Cache helper to bulk uncache pages on an inode. This will only work for the circumstance where the pages in the cache correspond 1:1 with the pages attached to an inode's page cache. This is required for CIFS and NFS: When disabling inode cookie, we were returning the cookie and setting cifsi->fscache to NULL but failed to invalidate any previously mapped pages. This resulted in "Bad page state" errors and manifested in other kind of errors when running fsstress. Fix it by uncaching mapped pages when we disable the inode cookie. This patch should fix the following oops and "Bad page state" errors seen during fsstress testing. ------------[ cut here ]------------ kernel BUG at fs/cachefiles/namei.c:201! invalid opcode: 0000 [#1] SMP Pid: 5, comm: kworker/u:0 Not tainted 2.6.38.7-30.fc15.x86_64 #1 Bochs Bochs RIP: 0010: cachefiles_walk_to_object+0x436/0x745 [cachefiles] RSP: 0018:ffff88002ce6dd00 EFLAGS: 00010282 RAX: ffff88002ef165f0 RBX: ffff88001811f500 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000100 RDI: 0000000000000282 RBP: ffff88002ce6dda0 R08: 0000000000000100 R09: ffffffff81b3a300 R10: 0000ffff00066c0a R11: 0000000000000003 R12: ffff88002ae54840 R13: ffff88002ae54840 R14: ffff880029c29c00 R15: ffff88001811f4b0 FS: 00007f394dd32720(0000) GS:ffff88002ef00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 00007fffcb62ddf8 CR3: 000000001825f000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process kworker/u:0 (pid: 5, threadinfo ffff88002ce6c000, task ffff88002ce55cc0) Stack: 0000000000000246 ffff88002ce55cc0 ffff88002ce6dd58 ffff88001815dc00 ffff8800185246c0 ffff88001811f618 ffff880029c29d18 ffff88001811f380 ffff88002ce6dd50 ffffffff814757e4 ffff88002ce6dda0 ffffffff8106ac56 Call Trace: cachefiles_lookup_object+0x78/0xd4 [cachefiles] fscache_lookup_object+0x131/0x16d [fscache] fscache_object_work_func+0x1bc/0x669 [fscache] process_one_work+0x186/0x298 worker_thread+0xda/0x15d kthread+0x84/0x8c kernel_thread_helper+0x4/0x10 RIP cachefiles_walk_to_object+0x436/0x745 [cachefiles] ---[ end trace 1d481c9af1804caa ]--- I tested the uncaching by the following means: (1) Create a big file on my NFS server (104857600 bytes). (2) Read the file into the cache with md5sum on the NFS client. Look in /proc/fs/fscache/stats: Pages : mrk=25601 unc=0 (3) Open the file for read/write ("bash 5<>/warthog/bigfile"). Look in proc again: Pages : mrk=25601 unc=25601 Reported-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-and-Tested-by: Suresh Jayaraman <sjayaraman@suse.de> cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
|
|
Amerigo Wang
|
e50c1f609c |
fscache: remove dead code under CONFIG_WORKQUEUE_DEBUGFS
There is no CONFIG_WORKQUEUE_DEBUGFS any more, so this code is dead. Signed-off-by: WANG Cong <amwang@redhat.com> Cc: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
|
|
Akshat Aranya
|
ba28b93a52 |
FS-Cache: Fix operation handling
fscache_submit_exclusive_op() adds an operation to the pending list if other operations are pending. Fix the check for pending ops as n_ops must be greater than 0 at the point it is checked as it is incremented immediately before under lock. Signed-off-by: Akshat Aranya <aranya@nec-labs.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
|
|
David Howells
|
12fdff3fc2 |
Add a dummy printk function for the maintenance of unused printks
Add a dummy printk function for the maintenance of unused printks through gcc format checking, and also so that side-effect checking is maintained too. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
|
|
Tejun Heo
|
40f2b6ffe5 |
fscache: fix build on !CONFIG_SYSCTL
Commit
|
|
|
Tejun Heo
|
d098adfb7d |
fscache: drop references to slow-work
fscache no longer uses slow-work. Drop references to it. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: David Howells <dhowells@redhat.com> |
|
|
Tejun Heo
|
8af7c12436 |
fscache: convert operation to use workqueue instead of slow-work
Make fscache operation to use only workqueue instead of combination of workqueue and slow-work. FSCACHE_OP_SLOW is dropped and FSCACHE_OP_FAST is renamed to FSCACHE_OP_ASYNC and uses newly added fscache_op_wq workqueue to execute op->processor(). fscache_operation_init_slow() is dropped and fscache_operation_init() now takes @processor argument directly. * Unbound workqueue is used. * fscache_retrieval_work() is no longer necessary as OP_ASYNC now does the equivalent thing. * sysctl fscache.operation_max_active added to control concurrency. The default value is nr_cpus clamped between 2 and WQ_UNBOUND_MAX_ACTIVE. * debugfs support is dropped for now. Tracing API based debug facility is planned to be added. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: David Howells <dhowells@redhat.com> |
|
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Tejun Heo
|
8b8edefa2f |
fscache: convert object to use workqueue instead of slow-work
Make fscache object state transition callbacks use workqueue instead of slow-work. New dedicated unbound CPU workqueue fscache_object_wq is created. get/put callbacks are renamed and modified to take @object and called directly from the enqueue wrapper and the work function. While at it, make all open coded instances of get/put to use fscache_get/put_object(). * Unbound workqueue is used. * work_busy() output is printed instead of slow-work flags in object debugging outputs. They mean basically the same thing bit-for-bit. * sysctl fscache.object_max_active added to control concurrency. The default value is nr_cpus clamped between 4 and WQ_UNBOUND_MAX_ACTIVE. * slow_work_sleep_till_thread_needed() is replaced with fscache private implementation fscache_object_sleep_till_congested() which waits on fscache_object_wq congestion. * debugfs support is dropped for now. Tracing API based debug facility is planned to be added. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: David Howells <dhowells@redhat.com> |
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Dan Carpenter
|
08a66859e6 |
FS-Cache: Remove unneeded null checks
fscache_write_op() makes unnecessary checks of the page variable to see if it is NULL. It can't be NULL at those points as the kernel would already have crashed a little higher up where we examined page->index. Furthermore, unless radix_tree_gang_lookup_tag() can return 1 but no page, a NULL pointer crash should not be encountered there as we can only get there if r_t_g_l_t() returned 1. Signed-off-by: Dan Carpenter <error27@gmail.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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|
Andrew Morton
|
cc68e3be74 |
fs/fscache/object-list.c: fix warning on 32-bit
fs/fscache/object-list.c: In function 'fscache_objlist_lookup': fs/fscache/object-list.c:105: warning: cast to pointer from integer of different size Acked-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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David Howells
|
cc4fc29e59 |
fs-cache: order the debugfs stats correctly
Order the debugfs statistics correctly. The values displayed through a
seq_printf() statement should be in the same order as the names in the
format string.
In the 'Lookups' line, objects created ('crt=') and lookups timed out
('tmo=') have their values transposed.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Tejun Heo
|
5a0e3ad6af |
include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> |
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David Howells
|
a53f4f9efa |
SLOW_WORK: CONFIG_SLOW_WORK_PROC should be CONFIG_SLOW_WORK_DEBUG
CONFIG_SLOW_WORK_PROC was changed to CONFIG_SLOW_WORK_DEBUG, but not in all instances. Change the remaining instances. This makes the debugfs file display the time mark and the owner's description again. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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|
Dan Carpenter
|
1147d0f915 |
fscache: add missing unlock
Sparse complained about this missing spin_unlock() Signed-off-by: Dan Carpenter <error27@gmail.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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|
Christian Kujau
|
d4014030d2 |
FS-Cache: Remove the EXPERIMENTAL flag
Remove the EXPERIMENTAL flag from FS-Cache so that Ubuntu can make use of the facility. Signed-off-by: Christian Kujau <lists@nerdbynature.de> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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|
David Howells
|
ea58ceb543 |
FS-Cache: Avoid maybe-used-uninitialised warning on variable
Andrew Morton's compiler sees the following warning in FS-Cache: fs/fscache/object-list.c: In function 'fscache_objlist_lookup': fs/fscache/object-list.c:94: warning: 'obj' may be used uninitialized in this function which my compiler doesn't. This is a false positive as obj can only be used in the comparison against minobj if minobj has been set to something other than NULL, but for that to happen, obj has to be first set to something. Deal with this by preclearing obj too. Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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|
David Howells
|
4fa9f4ede8 |
FS-Cache: Provide nop fscache_stat_d() if CONFIG_FSCACHE_STATS=n
Provide nop fscache_stat_d() macro if CONFIG_FSCACHE_STATS=n lest errors like the following occur: fs/fscache/cache.c: In function 'fscache_withdraw_cache': fs/fscache/cache.c:386: error: implicit declaration of function 'fscache_stat_d' fs/fscache/cache.c:386: error: 'fscache_n_cop_sync_cache' undeclared (first use in this function) fs/fscache/cache.c:386: error: (Each undeclared identifier is reported only once fs/fscache/cache.c:386: error: for each function it appears in.) fs/fscache/cache.c:392: error: 'fscache_n_cop_dissociate_pages' undeclared (first use in this function) Signed-off-by: David Howells <dhowells@redhat.com> |
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|
David Howells
|
fee096deb4 |
CacheFiles: Catch an overly long wait for an old active object
Catch an overly long wait for an old, dying active object when we want to
replace it with a new one. The probability is that all the slow-work threads
are hogged, and the delete can't get a look in.
What we do instead is:
(1) if there's nothing in the slow work queue, we sleep until either the dying
object has finished dying or there is something in the slow work queue
behind which we can queue our object.
(2) if there is something in the slow work queue, we return ETIMEDOUT to
fscache_lookup_object(), which then puts us back on the slow work queue,
presumably behind the deletion that we're blocked by. We are then
deferred for a while until we work our way back through the queue -
without blocking a slow-work thread unnecessarily.
A backtrace similar to the following may appear in the log without this patch:
INFO: task kslowd004:5711 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kslowd004 D 0000000000000000 0 5711 2 0x00000080
ffff88000340bb80 0000000000000046 ffff88002550d000 0000000000000000
ffff88002550d000 0000000000000007 ffff88000340bfd8 ffff88002550d2a8
000000000000ddf0 00000000000118c0 00000000000118c0 ffff88002550d2a8
Call Trace:
[<ffffffff81058e21>] ? trace_hardirqs_on+0xd/0xf
[<ffffffffa011c4d8>] ? cachefiles_wait_bit+0x0/0xd [cachefiles]
[<ffffffffa011c4e1>] cachefiles_wait_bit+0x9/0xd [cachefiles]
[<ffffffff81353153>] __wait_on_bit+0x43/0x76
[<ffffffff8111ae39>] ? ext3_xattr_get+0x1ec/0x270
[<ffffffff813531ef>] out_of_line_wait_on_bit+0x69/0x74
[<ffffffffa011c4d8>] ? cachefiles_wait_bit+0x0/0xd [cachefiles]
[<ffffffff8104c125>] ? wake_bit_function+0x0/0x2e
[<ffffffffa011bc79>] cachefiles_mark_object_active+0x203/0x23b [cachefiles]
[<ffffffffa011c209>] cachefiles_walk_to_object+0x558/0x827 [cachefiles]
[<ffffffffa011a429>] cachefiles_lookup_object+0xac/0x12a [cachefiles]
[<ffffffffa00aa1e9>] fscache_lookup_object+0x1c7/0x214 [fscache]
[<ffffffffa00aafc5>] fscache_object_state_machine+0xa5/0x52d [fscache]
[<ffffffffa00ab4ac>] fscache_object_slow_work_execute+0x5f/0xa0 [fscache]
[<ffffffff81082093>] slow_work_execute+0x18f/0x2d1
[<ffffffff8108239a>] slow_work_thread+0x1c5/0x308
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffff810821d5>] ? slow_work_thread+0x0/0x308
[<ffffffff8104be91>] kthread+0x7a/0x82
[<ffffffff8100beda>] child_rip+0xa/0x20
[<ffffffff8100b87c>] ? restore_args+0x0/0x30
[<ffffffff8104be17>] ? kthread+0x0/0x82
[<ffffffff8100bed0>] ? child_rip+0x0/0x20
1 lock held by kslowd004/5711:
#0: (&sb->s_type->i_mutex_key#7/1){+.+.+.}, at: [<ffffffffa011be64>] cachefiles_walk_to_object+0x1b3/0x827 [cachefiles]
Signed-off-by: David Howells <dhowells@redhat.com>
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|
|
David Howells
|
868411be3f |
FS-Cache: Actually requeue an object when requested
FS-Cache objects have an FSCACHE_OBJECT_EV_REQUEUE event that can theoretically be raised to ask the state machine to requeue the object for further processing before the work function returns to the slow-work facility. However, fscache_object_work_execute() was clearing that bit before checking the event mask to see whether the object has any pending events that require it to be requeued immediately. Instead, the bit should be cleared after the check and enqueue. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
60d543ca72 |
FS-Cache: Start processing an object's operations on that object's death
Start processing an object's operations when that object moves into the DYING state as the object cannot be destroyed until all its outstanding operations have completed. Furthermore, make sure that read and allocation operations handle being woken up on a dead object. Such events are recorded in the Allocs.abt and Retrvls.abt statistics as viewable through /proc/fs/fscache/stats. The code for waiting for object activation for the read and allocation operations is also extracted into its own function as it is much the same in all cases, differing only in the stats incremented. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
d461d26dde |
FS-Cache: Make sure FSCACHE_COOKIE_LOOKING_UP cleared on lookup failure
We must make sure that FSCACHE_COOKIE_LOOKING_UP is cleared on lookup failure (if an object reaches the LC_DYING state), and we should clear it before clearing FSCACHE_COOKIE_CREATING. If this doesn't happen then fscache_wait_for_deferred_lookup() may hold allocation and retrieval operations indefinitely until they're interrupted by signals - which in turn pins the dying object until they go away. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
2175bb06dc |
FS-Cache: Add a retirement stat counter
Add a stat counter to count retirement events rather than ordinary release events (the retire argument to fscache_relinquish_cookie()). Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
201a15428b |
FS-Cache: Handle pages pending storage that get evicted under OOM conditions
Handle netfs pages that the vmscan algorithm wants to evict from the pagecache
under OOM conditions, but that are waiting for write to the cache. Under these
conditions, vmscan calls the releasepage() function of the netfs, asking if a
page can be discarded.
The problem is typified by the following trace of a stuck process:
kslowd005 D 0000000000000000 0 4253 2 0x00000080
ffff88001b14f370 0000000000000046 ffff880020d0d000 0000000000000007
0000000000000006 0000000000000001 ffff88001b14ffd8 ffff880020d0d2a8
000000000000ddf0 00000000000118c0 00000000000118c0 ffff880020d0d2a8
Call Trace:
[<ffffffffa00782d8>] __fscache_wait_on_page_write+0x8b/0xa7 [fscache]
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffffa0078240>] ? __fscache_check_page_write+0x63/0x70 [fscache]
[<ffffffffa00b671d>] nfs_fscache_release_page+0x4e/0xc4 [nfs]
[<ffffffffa00927f0>] nfs_release_page+0x3c/0x41 [nfs]
[<ffffffff810885d3>] try_to_release_page+0x32/0x3b
[<ffffffff81093203>] shrink_page_list+0x316/0x4ac
[<ffffffff8109372b>] shrink_inactive_list+0x392/0x67c
[<ffffffff813532fa>] ? __mutex_unlock_slowpath+0x100/0x10b
[<ffffffff81058df0>] ? trace_hardirqs_on_caller+0x10c/0x130
[<ffffffff8135330e>] ? mutex_unlock+0x9/0xb
[<ffffffff81093aa2>] shrink_list+0x8d/0x8f
[<ffffffff81093d1c>] shrink_zone+0x278/0x33c
[<ffffffff81052d6c>] ? ktime_get_ts+0xad/0xba
[<ffffffff81094b13>] try_to_free_pages+0x22e/0x392
[<ffffffff81091e24>] ? isolate_pages_global+0x0/0x212
[<ffffffff8108e743>] __alloc_pages_nodemask+0x3dc/0x5cf
[<ffffffff81089529>] grab_cache_page_write_begin+0x65/0xaa
[<ffffffff8110f8c0>] ext3_write_begin+0x78/0x1eb
[<ffffffff81089ec5>] generic_file_buffered_write+0x109/0x28c
[<ffffffff8103cb69>] ? current_fs_time+0x22/0x29
[<ffffffff8108a509>] __generic_file_aio_write+0x350/0x385
[<ffffffff8108a588>] ? generic_file_aio_write+0x4a/0xae
[<ffffffff8108a59e>] generic_file_aio_write+0x60/0xae
[<ffffffff810b2e82>] do_sync_write+0xe3/0x120
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffff810b18e1>] ? __dentry_open+0x1a5/0x2b8
[<ffffffff810b1a76>] ? dentry_open+0x82/0x89
[<ffffffffa00e693c>] cachefiles_write_page+0x298/0x335 [cachefiles]
[<ffffffffa0077147>] fscache_write_op+0x178/0x2c2 [fscache]
[<ffffffffa0075656>] fscache_op_execute+0x7a/0xd1 [fscache]
[<ffffffff81082093>] slow_work_execute+0x18f/0x2d1
[<ffffffff8108239a>] slow_work_thread+0x1c5/0x308
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffff810821d5>] ? slow_work_thread+0x0/0x308
[<ffffffff8104be91>] kthread+0x7a/0x82
[<ffffffff8100beda>] child_rip+0xa/0x20
[<ffffffff8100b87c>] ? restore_args+0x0/0x30
[<ffffffff8102ef83>] ? tg_shares_up+0x171/0x227
[<ffffffff8104be17>] ? kthread+0x0/0x82
[<ffffffff8100bed0>] ? child_rip+0x0/0x20
In the above backtrace, the following is happening:
(1) A page storage operation is being executed by a slow-work thread
(fscache_write_op()).
(2) FS-Cache farms the operation out to the cache to perform
(cachefiles_write_page()).
(3) CacheFiles is then calling Ext3 to perform the actual write, using Ext3's
standard write (do_sync_write()) under KERNEL_DS directly from the netfs
page.
(4) However, for Ext3 to perform the write, it must allocate some memory, in
particular, it must allocate at least one page cache page into which it
can copy the data from the netfs page.
(5) Under OOM conditions, the memory allocator can't immediately come up with
a page, so it uses vmscan to find something to discard
(try_to_free_pages()).
(6) vmscan finds a clean netfs page it might be able to discard (possibly the
one it's trying to write out).
(7) The netfs is called to throw the page away (nfs_release_page()) - but it's
called with __GFP_WAIT, so the netfs decides to wait for the store to
complete (__fscache_wait_on_page_write()).
(8) This blocks a slow-work processing thread - possibly against itself.
The system ends up stuck because it can't write out any netfs pages to the
cache without allocating more memory.
To avoid this, we make FS-Cache cancel some writes that aren't in the middle of
actually being performed. This means that some data won't make it into the
cache this time. To support this, a new FS-Cache function is added
fscache_maybe_release_page() that replaces what the netfs releasepage()
functions used to do with respect to the cache.
The decisions fscache_maybe_release_page() makes are counted and displayed
through /proc/fs/fscache/stats on a line labelled "VmScan". There are four
counters provided: "nos=N" - pages that weren't pending storage; "gon=N" -
pages that were pending storage when we first looked, but weren't by the time
we got the object lock; "bsy=N" - pages that we ignored as they were actively
being written when we looked; and "can=N" - pages that we cancelled the storage
of.
What I'd really like to do is alter the behaviour of the cancellation
heuristics, depending on how necessary it is to expel pages. If there are
plenty of other pages that aren't waiting to be written to the cache that
could be ejected first, then it would be nice to hold up on immediate
cancellation of cache writes - but I don't see a way of doing that.
Signed-off-by: David Howells <dhowells@redhat.com>
|
|
|
David Howells
|
e3d4d28b1c |
FS-Cache: Handle read request vs lookup, creation or other cache failure
FS-Cache doesn't correctly handle the netfs requesting a read from the cache on an object that failed or was withdrawn by the cache. A trace similar to the following might be seen: CacheFiles: Lookup failed error -105 [exe ] unexpected submission OP165afe [OBJ6cac OBJECT_LC_DYING] [exe ] objstate=OBJECT_LC_DYING [OBJECT_LC_DYING] [exe ] objflags=0 [exe ] objevent=9 [fffffffffffffffb] [exe ] ops=0 inp=0 exc=0 Pid: 6970, comm: exe Not tainted 2.6.32-rc6-cachefs #50 Call Trace: [<ffffffffa0076477>] fscache_submit_op+0x3ff/0x45a [fscache] [<ffffffffa0077997>] __fscache_read_or_alloc_pages+0x187/0x3c4 [fscache] [<ffffffffa00b6480>] ? nfs_readpage_from_fscache_complete+0x0/0x66 [nfs] [<ffffffffa00b6388>] __nfs_readpages_from_fscache+0x7e/0x176 [nfs] [<ffffffff8108e483>] ? __alloc_pages_nodemask+0x11c/0x5cf [<ffffffffa009d796>] nfs_readpages+0x114/0x1d7 [nfs] [<ffffffff81090314>] __do_page_cache_readahead+0x15f/0x1ec [<ffffffff81090228>] ? __do_page_cache_readahead+0x73/0x1ec [<ffffffff810903bd>] ra_submit+0x1c/0x20 [<ffffffff810906bb>] ondemand_readahead+0x227/0x23a [<ffffffff81090762>] page_cache_sync_readahead+0x17/0x19 [<ffffffff8108a99e>] generic_file_aio_read+0x236/0x5a0 [<ffffffffa00937bd>] nfs_file_read+0xe4/0xf3 [nfs] [<ffffffff810b2fa2>] do_sync_read+0xe3/0x120 [<ffffffff81354cc3>] ? _spin_unlock_irq+0x2b/0x31 [<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34 [<ffffffff811848e5>] ? selinux_file_permission+0x5d/0x10f [<ffffffff81352bdb>] ? thread_return+0x3e/0x101 [<ffffffff8117d7b0>] ? security_file_permission+0x11/0x13 [<ffffffff810b3b06>] vfs_read+0xaa/0x16f [<ffffffff81058df0>] ? trace_hardirqs_on_caller+0x10c/0x130 [<ffffffff810b3c84>] sys_read+0x45/0x6c [<ffffffff8100ae2b>] system_call_fastpath+0x16/0x1b The object state might also be OBJECT_DYING or OBJECT_WITHDRAWING. This should be handled by simply rejecting the new operation with ENOBUFS. There's no need to log an error for it. Events of this type now appear in the stats file under Ops:rej. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
285e728b0a |
FS-Cache: Don't delete pending pages from the page-store tracking tree
Don't delete pending pages from the page-store tracking tree, but rather send them for another write as they've presumably been updated. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
1bccf513ac |
FS-Cache: Fix lock misorder in fscache_write_op()
FS-Cache has two structs internally for keeping track of the internal state of
a cached file: the fscache_cookie struct, which represents the netfs's state,
and fscache_object struct, which represents the cache's state. Each has a
pointer that points to the other (when both are in existence), and each has a
spinlock for pointer maintenance.
Since netfs operations approach these structures from the cookie side, they get
the cookie lock first, then the object lock. Cache operations, on the other
hand, approach from the object side, and get the object lock first. It is not
then permitted for a cache operation to get the cookie lock whilst it is
holding the object lock lest deadlock occur; instead, it must do one of two
things:
(1) increment the cookie usage counter, drop the object lock and then get both
locks in order, or
(2) simply hold the object lock as certain parts of the cookie may not be
altered whilst the object lock is held.
It is also not permitted to follow either pointer without holding the lock at
the end you start with. To break the pointers between the cookie and the
object, both locks must be held.
fscache_write_op(), however, violates the locking rules: It attempts to get the
cookie lock without (a) checking that the cookie pointer is a valid pointer,
and (b) holding the object lock to protect the cookie pointer whilst it follows
it. This is so that it can access the pending page store tree without
interference from __fscache_write_page().
This is fixed by splitting the cookie lock, such that the page store tracking
tree is protected by its own lock, and checking that the cookie pointer is
non-NULL before we attempt to follow it whilst holding the object lock.
The new lock is subordinate to both the cookie lock and the object lock, and so
should be taken after those.
Signed-off-by: David Howells <dhowells@redhat.com>
|
|
|
David Howells
|
6897e3df8f |
FS-Cache: The object-available state can't rely on the cookie to be available
The object-available state in the object processing state machine (as processed by fscache_object_available()) can't rely on the cookie to be available because the FSCACHE_COOKIE_CREATING bit may have been cleared by fscache_obtained_object() prior to the object being put into the FSCACHE_OBJECT_AVAILABLE state. Clearing the FSCACHE_COOKIE_CREATING bit on a cookie permits __fscache_relinquish_cookie() to proceed and detach the cookie from the object. To deal with this, we don't dereference object->cookie in fscache_object_available() if the object has already been detached. In addition, a couple of assertions are added into fscache_drop_object() to make sure the object is unbound from the cookie before it gets there. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
5753c44188 |
FS-Cache: Permit cache retrieval ops to be interrupted in the initial wait phase
Permit the operations to retrieve data from the cache or to allocate space in the cache for future writes to be interrupted whilst they're waiting for permission for the operation to proceed. Typically this wait occurs whilst the cache object is being looked up on disk in the background. If an interruption occurs, and the operation has not yet been given the go-ahead to run, the operation is dequeued and cancelled, and control returns to the read operation of the netfs routine with none of the requested pages having been read or in any way marked as known by the cache. This means that the initial wait is done interruptibly rather than uninterruptibly. In addition, extra stats values are made available to show the number of ops cancelled and the number of cache space allocations interrupted. Signed-off-by: David Howells <dhowells@redhat.com> |
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|
David Howells
|
b34df792b4 |
FS-Cache: Use radix tree preload correctly in tracking of pages to be stored
__fscache_write_page() attempts to load the radix tree preallocation pool for the CPU it is on before calling radix_tree_insert(), as the insertion must be done inside a pair of spinlocks. Use of the preallocation pool, however, is contingent on the radix tree being initialised without __GFP_WAIT specified. __fscache_acquire_cookie() was passing GFP_NOFS to INIT_RADIX_TREE() - but that includes __GFP_WAIT. The solution is to AND out __GFP_WAIT. Additionally, the banner comment to radix_tree_preload() is altered to make note of this prerequisite. Possibly there should be a WARN_ON() too. Without this fix, I have seen the following recursive deadlock caused by radix_tree_insert() attempting to allocate memory inside the spinlocked region, which resulted in FS-Cache being called back into to release memory - which required the spinlock already held. ============================================= [ INFO: possible recursive locking detected ] 2.6.32-rc6-cachefs #24 --------------------------------------------- nfsiod/7916 is trying to acquire lock: (&cookie->lock){+.+.-.}, at: [<ffffffffa0076872>] __fscache_uncache_page+0xdb/0x160 [fscache] but task is already holding lock: (&cookie->lock){+.+.-.}, at: [<ffffffffa0076acc>] __fscache_write_page+0x15c/0x3f3 [fscache] other info that might help us debug this: 5 locks held by nfsiod/7916: #0: (nfsiod){+.+.+.}, at: [<ffffffff81048290>] worker_thread+0x19a/0x2e2 #1: (&task->u.tk_work#2){+.+.+.}, at: [<ffffffff81048290>] worker_thread+0x19a/0x2e2 #2: (&cookie->lock){+.+.-.}, at: [<ffffffffa0076acc>] __fscache_write_page+0x15c/0x3f3 [fscache] #3: (&object->lock#2){+.+.-.}, at: [<ffffffffa0076b07>] __fscache_write_page+0x197/0x3f3 [fscache] #4: (&cookie->stores_lock){+.+...}, at: [<ffffffffa0076b0f>] __fscache_write_page+0x19f/0x3f3 [fscache] stack backtrace: Pid: 7916, comm: nfsiod Not tainted 2.6.32-rc6-cachefs #24 Call Trace: [<ffffffff8105ac7f>] __lock_acquire+0x1649/0x16e3 [<ffffffff81059ded>] ? __lock_acquire+0x7b7/0x16e3 [<ffffffff8100e27d>] ? dump_trace+0x248/0x257 [<ffffffff8105ad70>] lock_acquire+0x57/0x6d [<ffffffffa0076872>] ? __fscache_uncache_page+0xdb/0x160 [fscache] [<ffffffff8135467c>] _spin_lock+0x2c/0x3b [<ffffffffa0076872>] ? __fscache_uncache_page+0xdb/0x160 [fscache] [<ffffffffa0076872>] __fscache_uncache_page+0xdb/0x160 [fscache] [<ffffffffa0077eb7>] ? __fscache_check_page_write+0x0/0x71 [fscache] [<ffffffffa00b4755>] nfs_fscache_release_page+0x86/0xc4 [nfs] [<ffffffffa00907f0>] nfs_release_page+0x3c/0x41 [nfs] [<ffffffff81087ffb>] try_to_release_page+0x32/0x3b [<ffffffff81092c2b>] shrink_page_list+0x316/0x4ac [<ffffffff81058a9b>] ? mark_held_locks+0x52/0x70 [<ffffffff8135451b>] ? _spin_unlock_irq+0x2b/0x31 [<ffffffff81093153>] shrink_inactive_list+0x392/0x67c [<ffffffff81058a9b>] ? mark_held_locks+0x52/0x70 [<ffffffff810934ca>] shrink_list+0x8d/0x8f [<ffffffff81093744>] shrink_zone+0x278/0x33c [<ffffffff81052c70>] ? ktime_get_ts+0xad/0xba [<ffffffff8109453b>] try_to_free_pages+0x22e/0x392 [<ffffffff8109184c>] ? isolate_pages_global+0x0/0x212 [<ffffffff8108e16b>] __alloc_pages_nodemask+0x3dc/0x5cf [<ffffffff810ae24a>] cache_alloc_refill+0x34d/0x6c1 [<ffffffff811bcf74>] ? radix_tree_node_alloc+0x52/0x5c [<ffffffff810ae929>] kmem_cache_alloc+0xb2/0x118 [<ffffffff811bcf74>] radix_tree_node_alloc+0x52/0x5c [<ffffffff811bcfd5>] radix_tree_insert+0x57/0x19c [<ffffffffa0076b53>] __fscache_write_page+0x1e3/0x3f3 [fscache] [<ffffffffa00b4248>] __nfs_readpage_to_fscache+0x58/0x11e [nfs] [<ffffffffa009bb77>] nfs_readpage_release+0x34/0x9b [nfs] [<ffffffffa009c0d9>] nfs_readpage_release_full+0x32/0x4b [nfs] [<ffffffffa0006cff>] rpc_release_calldata+0x12/0x14 [sunrpc] [<ffffffffa0006e2d>] rpc_free_task+0x59/0x61 [sunrpc] [<ffffffffa0006f03>] rpc_async_release+0x10/0x12 [sunrpc] [<ffffffff810482e5>] worker_thread+0x1ef/0x2e2 [<ffffffff81048290>] ? worker_thread+0x19a/0x2e2 [<ffffffff81352433>] ? thread_return+0x3e/0x101 [<ffffffffa0006ef3>] ? rpc_async_release+0x0/0x12 [sunrpc] [<ffffffff8104bff5>] ? autoremove_wake_function+0x0/0x34 [<ffffffff81058d25>] ? trace_hardirqs_on+0xd/0xf [<ffffffff810480f6>] ? worker_thread+0x0/0x2e2 [<ffffffff8104bd21>] kthread+0x7a/0x82 [<ffffffff8100beda>] child_rip+0xa/0x20 [<ffffffff8100b87c>] ? restore_args+0x0/0x30 [<ffffffff8104c2b9>] ? add_wait_queue+0x15/0x44 [<ffffffff8104bca7>] ? kthread+0x0/0x82 [<ffffffff8100bed0>] ? child_rip+0x0/0x20 Signed-off-by: David Howells <dhowells@redhat.com> |
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|
David Howells
|
7e311a207d |
FS-Cache: Clear netfs pointers in cookie after detaching object, not before
Clear the pointers from the fscache_cookie struct to netfs private data after clearing the pointer to the cookie from the fscache_object struct and releasing the object lock, rather than before. This allows the netfs private data pointers to be relied on simply by holding the object lock, rather than having to hold the cookie lock. This is makes things simpler as the cookie lock has to be taken before the object lock, but sometimes the object pointer is all that the code has. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
52bd75fdb1 |
FS-Cache: Add counters for entry/exit to/from cache operation functions
Count entries to and exits from cache operation table functions. Maintain these as a single counter that's added to or removed from as appropriate. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
4fbf4291aa |
FS-Cache: Allow the current state of all objects to be dumped
Allow the current state of all fscache objects to be dumped by doing: cat /proc/fs/fscache/objects By default, all objects and all fields will be shown. This can be restricted by adding a suitable key to one of the caller's keyrings (such as the session keyring): keyctl add user fscache:objlist "<restrictions>" @s The <restrictions> are: K Show hexdump of object key (don't show if not given) A Show hexdump of object aux data (don't show if not given) And paired restrictions: C Show objects that have a cookie c Show objects that don't have a cookie B Show objects that are busy b Show objects that aren't busy W Show objects that have pending writes w Show objects that don't have pending writes R Show objects that have outstanding reads r Show objects that don't have outstanding reads S Show objects that have slow work queued s Show objects that don't have slow work queued If neither side of a restriction pair is given, then both are implied. For example: keyctl add user fscache:objlist KB @s shows objects that are busy, and lists their object keys, but does not dump their auxiliary data. It also implies "CcWwRrSs", but as 'B' is given, 'b' is not implied. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
440f0affe2 |
FS-Cache: Annotate slow-work runqueue proc lines for FS-Cache work items
Annotate slow-work runqueue proc lines for FS-Cache work items. Objects include the object ID and the state. Operations include the object ID, the operation ID and the operation type and state. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
3d7a641e54 |
SLOW_WORK: Wait for outstanding work items belonging to a module to clear
Wait for outstanding slow work items belonging to a module to clear when unregistering that module as a user of the facility. This prevents the put_ref code of a work item from being taken away before it returns. Signed-off-by: David Howells <dhowells@redhat.com> |
|
|
David Howells
|
348ca1029e |
FS-Cache: Fixup renamed filenames in comments in internal.h
Fix up renamed filenames in comments in fs/fscache/internal.h. Originally, the files were all called fsc-xxx.c, but they got renamed to just xxx.c. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
|
|
David Howells
|
b510882281 |
FS-Cache: Implement data I/O part of netfs API
Implement the data I/O part of the FS-Cache netfs API. The documentation and
API header file were added in a previous patch.
This patch implements the following functions for the netfs to call:
(*) fscache_attr_changed().
Indicate that the object has changed its attributes. The only attribute
currently recorded is the file size. Only pages within the set file size
will be stored in the cache.
This operation is submitted for asynchronous processing, and will return
immediately. It will return -ENOMEM if an out of memory error is
encountered, -ENOBUFS if the object is not actually cached, or 0 if the
operation is successfully queued.
(*) fscache_read_or_alloc_page().
(*) fscache_read_or_alloc_pages().
Request data be fetched from the disk, and allocate internal metadata to
track the netfs pages and reserve disk space for unknown pages.
These operations perform semi-asynchronous data reads. Upon returning
they will indicate which pages they think can be retrieved from disk, and
will have set in progress attempts to retrieve those pages.
These will return, in order of preference, -ENOMEM on memory allocation
error, -ERESTARTSYS if a signal interrupted proceedings, -ENODATA if one
or more requested pages are not yet cached, -ENOBUFS if the object is not
actually cached or if there isn't space for future pages to be cached on
this object, or 0 if successful.
In the case of the multipage function, the pages for which reads are set
in progress will be removed from the list and the page count decreased
appropriately.
If any read operations should fail, the completion function will be given
an error, and will also be passed contextual information to allow the
netfs to fall back to querying the server for the absent pages.
For each successful read, the page completion function will also be
called.
Any pages subsequently tracked by the cache will have PG_fscache set upon
them on return. fscache_uncache_page() must be called for such pages.
If supplied by the netfs, the mark_pages_cached() cookie op will be
invoked for any pages now tracked.
(*) fscache_alloc_page().
Allocate internal metadata to track a netfs page and reserve disk space.
This will return -ENOMEM on memory allocation error, -ERESTARTSYS on
signal, -ENOBUFS if the object isn't cached, or there isn't enough space
in the cache, or 0 if successful.
Any pages subsequently tracked by the cache will have PG_fscache set upon
them on return. fscache_uncache_page() must be called for such pages.
If supplied by the netfs, the mark_pages_cached() cookie op will be
invoked for any pages now tracked.
(*) fscache_write_page().
Request data be stored to disk. This may only be called on pages that
have been read or alloc'd by the above three functions and have not yet
been uncached.
This will return -ENOMEM on memory allocation error, -ERESTARTSYS on
signal, -ENOBUFS if the object isn't cached, or there isn't immediately
enough space in the cache, or 0 if successful.
On a successful return, this operation will have queued the page for
asynchronous writing to the cache. The page will be returned with
PG_fscache_write set until the write completes one way or another. The
caller will not be notified if the write fails due to an I/O error. If
that happens, the object will become available and all pending writes will
be aborted.
Note that the cache may batch up page writes, and so it may take a while
to get around to writing them out.
The caller must assume that until PG_fscache_write is cleared the page is
use by the cache. Any changes made to the page may be reflected on disk.
The page may even be under DMA.
(*) fscache_uncache_page().
Indicate that the cache should stop tracking a page previously read or
alloc'd from the cache. If the page was alloc'd only, but unwritten, it
will not appear on disk.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
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|
|
David Howells
|
952efe7b78 |
FS-Cache: Add and document asynchronous operation handling
Add and document asynchronous operation handling for use by FS-Cache's data
storage and retrieval routines.
The following documentation is added to:
Documentation/filesystems/caching/operations.txt
================================
ASYNCHRONOUS OPERATIONS HANDLING
================================
========
OVERVIEW
========
FS-Cache has an asynchronous operations handling facility that it uses for its
data storage and retrieval routines. Its operations are represented by
fscache_operation structs, though these are usually embedded into some other
structure.
This facility is available to and expected to be be used by the cache backends,
and FS-Cache will create operations and pass them off to the appropriate cache
backend for completion.
To make use of this facility, <linux/fscache-cache.h> should be #included.
===============================
OPERATION RECORD INITIALISATION
===============================
An operation is recorded in an fscache_operation struct:
struct fscache_operation {
union {
struct work_struct fast_work;
struct slow_work slow_work;
};
unsigned long flags;
fscache_operation_processor_t processor;
...
};
Someone wanting to issue an operation should allocate something with this
struct embedded in it. They should initialise it by calling:
void fscache_operation_init(struct fscache_operation *op,
fscache_operation_release_t release);
with the operation to be initialised and the release function to use.
The op->flags parameter should be set to indicate the CPU time provision and
the exclusivity (see the Parameters section).
The op->fast_work, op->slow_work and op->processor flags should be set as
appropriate for the CPU time provision (see the Parameters section).
FSCACHE_OP_WAITING may be set in op->flags prior to each submission of the
operation and waited for afterwards.
==========
PARAMETERS
==========
There are a number of parameters that can be set in the operation record's flag
parameter. There are three options for the provision of CPU time in these
operations:
(1) The operation may be done synchronously (FSCACHE_OP_MYTHREAD). A thread
may decide it wants to handle an operation itself without deferring it to
another thread.
This is, for example, used in read operations for calling readpages() on
the backing filesystem in CacheFiles. Although readpages() does an
asynchronous data fetch, the determination of whether pages exist is done
synchronously - and the netfs does not proceed until this has been
determined.
If this option is to be used, FSCACHE_OP_WAITING must be set in op->flags
before submitting the operation, and the operating thread must wait for it
to be cleared before proceeding:
wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
fscache_wait_bit, TASK_UNINTERRUPTIBLE);
(2) The operation may be fast asynchronous (FSCACHE_OP_FAST), in which case it
will be given to keventd to process. Such an operation is not permitted
to sleep on I/O.
This is, for example, used by CacheFiles to copy data from a backing fs
page to a netfs page after the backing fs has read the page in.
If this option is used, op->fast_work and op->processor must be
initialised before submitting the operation:
INIT_WORK(&op->fast_work, do_some_work);
(3) The operation may be slow asynchronous (FSCACHE_OP_SLOW), in which case it
will be given to the slow work facility to process. Such an operation is
permitted to sleep on I/O.
This is, for example, used by FS-Cache to handle background writes of
pages that have just been fetched from a remote server.
If this option is used, op->slow_work and op->processor must be
initialised before submitting the operation:
fscache_operation_init_slow(op, processor)
Furthermore, operations may be one of two types:
(1) Exclusive (FSCACHE_OP_EXCLUSIVE). Operations of this type may not run in
conjunction with any other operation on the object being operated upon.
An example of this is the attribute change operation, in which the file
being written to may need truncation.
(2) Shareable. Operations of this type may be running simultaneously. It's
up to the operation implementation to prevent interference between other
operations running at the same time.
=========
PROCEDURE
=========
Operations are used through the following procedure:
(1) The submitting thread must allocate the operation and initialise it
itself. Normally this would be part of a more specific structure with the
generic op embedded within.
(2) The submitting thread must then submit the operation for processing using
one of the following two functions:
int fscache_submit_op(struct fscache_object *object,
struct fscache_operation *op);
int fscache_submit_exclusive_op(struct fscache_object *object,
struct fscache_operation *op);
The first function should be used to submit non-exclusive ops and the
second to submit exclusive ones. The caller must still set the
FSCACHE_OP_EXCLUSIVE flag.
If successful, both functions will assign the operation to the specified
object and return 0. -ENOBUFS will be returned if the object specified is
permanently unavailable.
The operation manager will defer operations on an object that is still
undergoing lookup or creation. The operation will also be deferred if an
operation of conflicting exclusivity is in progress on the object.
If the operation is asynchronous, the manager will retain a reference to
it, so the caller should put their reference to it by passing it to:
void fscache_put_operation(struct fscache_operation *op);
(3) If the submitting thread wants to do the work itself, and has marked the
operation with FSCACHE_OP_MYTHREAD, then it should monitor
FSCACHE_OP_WAITING as described above and check the state of the object if
necessary (the object might have died whilst the thread was waiting).
When it has finished doing its processing, it should call
fscache_put_operation() on it.
(4) The operation holds an effective lock upon the object, preventing other
exclusive ops conflicting until it is released. The operation can be
enqueued for further immediate asynchronous processing by adjusting the
CPU time provisioning option if necessary, eg:
op->flags &= ~FSCACHE_OP_TYPE;
op->flags |= ~FSCACHE_OP_FAST;
and calling:
void fscache_enqueue_operation(struct fscache_operation *op)
This can be used to allow other things to have use of the worker thread
pools.
=====================
ASYNCHRONOUS CALLBACK
=====================
When used in asynchronous mode, the worker thread pool will invoke the
processor method with a pointer to the operation. This should then get at the
container struct by using container_of():
static void fscache_write_op(struct fscache_operation *_op)
{
struct fscache_storage *op =
container_of(_op, struct fscache_storage, op);
...
}
The caller holds a reference on the operation, and will invoke
fscache_put_operation() when the processor function returns. The processor
function is at liberty to call fscache_enqueue_operation() or to take extra
references.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
|
|
|
David Howells
|
ccc4fc3d11 |
FS-Cache: Implement the cookie management part of the netfs API
Implement the cookie management part of the FS-Cache netfs client API. The
documentation and API header file were added in a previous patch.
This patch implements the following three functions:
(1) fscache_acquire_cookie().
Acquire a cookie to represent an object to the netfs. If the object in
question is a non-index object, then that object and its parent indices
will be created on disk at this point if they don't already exist. Index
creation is deferred because an index may reside in multiple caches.
(2) fscache_relinquish_cookie().
Retire or release a cookie previously acquired. At this point, the
object on disk may be destroyed.
(3) fscache_update_cookie().
Update the in-cache representation of a cookie. This is used to update
the auxiliary data for coherency management purposes.
With this patch it is possible to have a netfs instruct a cache backend to
look up, validate and create metadata on disk and to destroy it again.
The ability to actually store and retrieve data in the objects so created is
added in later patches.
Note that these functions will never return an error. _All_ errors are
handled internally to FS-Cache.
The worst that can happen is that fscache_acquire_cookie() may return a NULL
pointer - which is considered a negative cookie pointer and can be passed back
to any function that takes a cookie without harm. A negative cookie pointer
merely suppresses caching at that level.
The stub in linux/fscache.h will detect inline the negative cookie pointer and
abort the operation as fast as possible. This means that the compiler doesn't
have to set up for a call in that case.
See the documentation in Documentation/filesystems/caching/netfs-api.txt for
more information.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
|
|
|
David Howells
|
36c9559022 |
FS-Cache: Object management state machine
Implement the cache object management state machine.
The following documentation is added to illuminate the working of this state
machine. It will also be added as:
Documentation/filesystems/caching/object.txt
====================================================
IN-KERNEL CACHE OBJECT REPRESENTATION AND MANAGEMENT
====================================================
==============
REPRESENTATION
==============
FS-Cache maintains an in-kernel representation of each object that a netfs is
currently interested in. Such objects are represented by the fscache_cookie
struct and are referred to as cookies.
FS-Cache also maintains a separate in-kernel representation of the objects that
a cache backend is currently actively caching. Such objects are represented by
the fscache_object struct. The cache backends allocate these upon request, and
are expected to embed them in their own representations. These are referred to
as objects.
There is a 1:N relationship between cookies and objects. A cookie may be
represented by multiple objects - an index may exist in more than one cache -
or even by no objects (it may not be cached).
Furthermore, both cookies and objects are hierarchical. The two hierarchies
correspond, but the cookies tree is a superset of the union of the object trees
of multiple caches:
NETFS INDEX TREE : CACHE 1 : CACHE 2
: :
: +-----------+ :
+----------->| IObject | :
+-----------+ | : +-----------+ :
| ICookie |-------+ : | :
+-----------+ | : | : +-----------+
| +------------------------------>| IObject |
| : | : +-----------+
| : V : |
| : +-----------+ : |
V +----------->| IObject | : |
+-----------+ | : +-----------+ : |
| ICookie |-------+ : | : V
+-----------+ | : | : +-----------+
| +------------------------------>| IObject |
+-----+-----+ : | : +-----------+
| | : | : |
V | : V : |
+-----------+ | : +-----------+ : |
| ICookie |------------------------->| IObject | : |
+-----------+ | : +-----------+ : |
| V : | : V
| +-----------+ : | : +-----------+
| | ICookie |-------------------------------->| IObject |
| +-----------+ : | : +-----------+
V | : V : |
+-----------+ | : +-----------+ : |
| DCookie |------------------------->| DObject | : |
+-----------+ | : +-----------+ : |
| : : |
+-------+-------+ : : |
| | : : |
V V : : V
+-----------+ +-----------+ : : +-----------+
| DCookie | | DCookie |------------------------>| DObject |
+-----------+ +-----------+ : : +-----------+
: :
In the above illustration, ICookie and IObject represent indices and DCookie
and DObject represent data storage objects. Indices may have representation in
multiple caches, but currently, non-index objects may not. Objects of any type
may also be entirely unrepresented.
As far as the netfs API goes, the netfs is only actually permitted to see
pointers to the cookies. The cookies themselves and any objects attached to
those cookies are hidden from it.
===============================
OBJECT MANAGEMENT STATE MACHINE
===============================
Within FS-Cache, each active object is managed by its own individual state
machine. The state for an object is kept in the fscache_object struct, in
object->state. A cookie may point to a set of objects that are in different
states.
Each state has an action associated with it that is invoked when the machine
wakes up in that state. There are four logical sets of states:
(1) Preparation: states that wait for the parent objects to become ready. The
representations are hierarchical, and it is expected that an object must
be created or accessed with respect to its parent object.
(2) Initialisation: states that perform lookups in the cache and validate
what's found and that create on disk any missing metadata.
(3) Normal running: states that allow netfs operations on objects to proceed
and that update the state of objects.
(4) Termination: states that detach objects from their netfs cookies, that
delete objects from disk, that handle disk and system errors and that free
up in-memory resources.
In most cases, transitioning between states is in response to signalled events.
When a state has finished processing, it will usually set the mask of events in
which it is interested (object->event_mask) and relinquish the worker thread.
Then when an event is raised (by calling fscache_raise_event()), if the event
is not masked, the object will be queued for processing (by calling
fscache_enqueue_object()).
PROVISION OF CPU TIME
---------------------
The work to be done by the various states is given CPU time by the threads of
the slow work facility (see Documentation/slow-work.txt). This is used in
preference to the workqueue facility because:
(1) Threads may be completely occupied for very long periods of time by a
particular work item. These state actions may be doing sequences of
synchronous, journalled disk accesses (lookup, mkdir, create, setxattr,
getxattr, truncate, unlink, rmdir, rename).
(2) Threads may do little actual work, but may rather spend a lot of time
sleeping on I/O. This means that single-threaded and 1-per-CPU-threaded
workqueues don't necessarily have the right numbers of threads.
LOCKING SIMPLIFICATION
----------------------
Because only one worker thread may be operating on any particular object's
state machine at once, this simplifies the locking, particularly with respect
to disconnecting the netfs's representation of a cache object (fscache_cookie)
from the cache backend's representation (fscache_object) - which may be
requested from either end.
=================
THE SET OF STATES
=================
The object state machine has a set of states that it can be in. There are
preparation states in which the object sets itself up and waits for its parent
object to transit to a state that allows access to its children:
(1) State FSCACHE_OBJECT_INIT.
Initialise the object and wait for the parent object to become active. In
the cache, it is expected that it will not be possible to look an object
up from the parent object, until that parent object itself has been looked
up.
There are initialisation states in which the object sets itself up and accesses
disk for the object metadata:
(2) State FSCACHE_OBJECT_LOOKING_UP.
Look up the object on disk, using the parent as a starting point.
FS-Cache expects the cache backend to probe the cache to see whether this
object is represented there, and if it is, to see if it's valid (coherency
management).
The cache should call fscache_object_lookup_negative() to indicate lookup
failure for whatever reason, and should call fscache_obtained_object() to
indicate success.
At the completion of lookup, FS-Cache will let the netfs go ahead with
read operations, no matter whether the file is yet cached. If not yet
cached, read operations will be immediately rejected with ENODATA until
the first known page is uncached - as to that point there can be no data
to be read out of the cache for that file that isn't currently also held
in the pagecache.
(3) State FSCACHE_OBJECT_CREATING.
Create an object on disk, using the parent as a starting point. This
happens if the lookup failed to find the object, or if the object's
coherency data indicated what's on disk is out of date. In this state,
FS-Cache expects the cache to create
The cache should call fscache_obtained_object() if creation completes
successfully, fscache_object_lookup_negative() otherwise.
At the completion of creation, FS-Cache will start processing write
operations the netfs has queued for an object. If creation failed, the
write ops will be transparently discarded, and nothing recorded in the
cache.
There are some normal running states in which the object spends its time
servicing netfs requests:
(4) State FSCACHE_OBJECT_AVAILABLE.
A transient state in which pending operations are started, child objects
are permitted to advance from FSCACHE_OBJECT_INIT state, and temporary
lookup data is freed.
(5) State FSCACHE_OBJECT_ACTIVE.
The normal running state. In this state, requests the netfs makes will be
passed on to the cache.
(6) State FSCACHE_OBJECT_UPDATING.
The state machine comes here to update the object in the cache from the
netfs's records. This involves updating the auxiliary data that is used
to maintain coherency.
And there are terminal states in which an object cleans itself up, deallocates
memory and potentially deletes stuff from disk:
(7) State FSCACHE_OBJECT_LC_DYING.
The object comes here if it is dying because of a lookup or creation
error. This would be due to a disk error or system error of some sort.
Temporary data is cleaned up, and the parent is released.
(8) State FSCACHE_OBJECT_DYING.
The object comes here if it is dying due to an error, because its parent
cookie has been relinquished by the netfs or because the cache is being
withdrawn.
Any child objects waiting on this one are given CPU time so that they too
can destroy themselves. This object waits for all its children to go away
before advancing to the next state.
(9) State FSCACHE_OBJECT_ABORT_INIT.
The object comes to this state if it was waiting on its parent in
FSCACHE_OBJECT_INIT, but its parent died. The object will destroy itself
so that the parent may proceed from the FSCACHE_OBJECT_DYING state.
(10) State FSCACHE_OBJECT_RELEASING.
(11) State FSCACHE_OBJECT_RECYCLING.
The object comes to one of these two states when dying once it is rid of
all its children, if it is dying because the netfs relinquished its
cookie. In the first state, the cached data is expected to persist, and
in the second it will be deleted.
(12) State FSCACHE_OBJECT_WITHDRAWING.
The object transits to this state if the cache decides it wants to
withdraw the object from service, perhaps to make space, but also due to
error or just because the whole cache is being withdrawn.
(13) State FSCACHE_OBJECT_DEAD.
The object transits to this state when the in-memory object record is
ready to be deleted. The object processor shouldn't ever see an object in
this state.
THE SET OF EVENTS
-----------------
There are a number of events that can be raised to an object state machine:
(*) FSCACHE_OBJECT_EV_UPDATE
The netfs requested that an object be updated. The state machine will ask
the cache backend to update the object, and the cache backend will ask the
netfs for details of the change through its cookie definition ops.
(*) FSCACHE_OBJECT_EV_CLEARED
This is signalled in two circumstances:
(a) when an object's last child object is dropped and
(b) when the last operation outstanding on an object is completed.
This is used to proceed from the dying state.
(*) FSCACHE_OBJECT_EV_ERROR
This is signalled when an I/O error occurs during the processing of some
object.
(*) FSCACHE_OBJECT_EV_RELEASE
(*) FSCACHE_OBJECT_EV_RETIRE
These are signalled when the netfs relinquishes a cookie it was using.
The event selected depends on whether the netfs asks for the backing
object to be retired (deleted) or retained.
(*) FSCACHE_OBJECT_EV_WITHDRAW
This is signalled when the cache backend wants to withdraw an object.
This means that the object will have to be detached from the netfs's
cookie.
Because the withdrawing releasing/retiring events are all handled by the object
state machine, it doesn't matter if there's a collision with both ends trying
to sever the connection at the same time. The state machine can just pick
which one it wants to honour, and that effects the other.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
|
|
|
David Howells
|
2868cbea72 |
FS-Cache: Bit waiting helpers
Add helpers for use with wait_on_bit(). Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com> |
|
|
David Howells
|
726dd7ff10 |
FS-Cache: Add netfs registration
Add functions to register and unregister a network filesystem or other client of the FS-Cache service. This allocates and releases the cookie representing the top-level index for a netfs, and makes it available to the netfs. If the FS-Cache facility is disabled, then the calls are optimised away at compile time. Note that whilst this patch may appear to work with FS-Cache enabled and a netfs attempting to use it, it will leak the cookie it allocates for the netfs as fscache_relinquish_cookie() is implemented in a later patch. This will cause the slab code to emit a warning when the module is removed. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com> |
|
|
David Howells
|
955d00917f |
FS-Cache: Provide a slab for cookie allocation
Provide a slab from which can be allocated the FS-Cache cookies that will be presented to the netfs. Also provide a slab constructor and a function to recursively discard a cookie and its ancestor chain. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com> |
|
|
David Howells
|
4c515dd47a |
FS-Cache: Add cache management
Implement the entry points by which a cache backend may initialise, add, declare an error upon and withdraw a cache. Further, an object is created in sysfs under which each cache added will get an object created: /sys/fs/fscache/<cachetag>/ All of this is described in Documentation/filesystems/caching/backend-api.txt added by a previous patch. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com> |
|
|
David Howells
|
0e04d4cefc |
FS-Cache: Add cache tag handling
Implement two features of FS-Cache:
(1) The ability to request and release cache tags - names by which a cache may
be known to a netfs, and thus selected for use.
(2) An internal function by which a cache is selected by consulting the netfs,
if the netfs wishes to be consulted.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
|
|
|
David Howells
|
a6891645cf |
FS-Cache: Root index definition
Add a description of the root index of the cache for later patches to make use
of.
The root index is owned by FS-Cache itself. When a netfs requests caching
facilities, FS-Cache will, if one doesn't already exist, create an entry in
the root index with the key being the name of the netfs ("AFS" for example),
and the auxiliary data holding the index structure version supplied by the
netfs:
FSDEF
|
+-----------+
| |
NFS AFS
[v=1] [v=1]
If an entry with the appropriate name does already exist, the version is
compared. If the version is different, the entire subtree from that entry
will be discarded and a new entry created.
The new entry will be an index, and a cookie referring to it will be passed to
the netfs. This is then the root handle by which the netfs accesses the
cache. It can create whatever objects it likes in that index, including
further indices.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
|
|
|
David Howells
|
7394daa8c6 |
FS-Cache: Add use of /proc and presentation of statistics
Make FS-Cache create its /proc interface and present various statistical information through it. Also provide the functions for updating this information. These features are enabled by: CONFIG_FSCACHE_PROC CONFIG_FSCACHE_STATS CONFIG_FSCACHE_HISTOGRAM The /proc directory for FS-Cache is also exported so that caching modules can add their own statistics there too. The FS-Cache module is loadable at this point, and the statistics files can be examined by userspace: cat /proc/fs/fscache/stats cat /proc/fs/fscache/histogram Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com> |
|
|
David Howells
|
06b3db1b9b |
FS-Cache: Add main configuration option, module entry points and debugging
Add the main configuration option, allowing FS-Cache to be selected; the module entry and exit functions and the debugging stuff used by these patches. The two configuration options added are: CONFIG_FSCACHE CONFIG_FSCACHE_DEBUG The first enables the facility, and the second makes the debugging statements enableable through the "debug" module parameter. The value of this parameter is a bitmask as described in: Documentation/filesystems/caching/fscache.txt The module can be loaded at this point, but all it will do at this point in the patch series is to start up the slow work facility and shut it down again. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com> |