This patch adds core functions for request-based dm.
When struct mapped device (md) is initialized, md->queue has
an I/O scheduler and the following functions are used for
request-based dm as the queue functions:
make_request_fn: dm_make_request()
pref_fn: dm_prep_fn()
request_fn: dm_request_fn()
softirq_done_fn: dm_softirq_done()
lld_busy_fn: dm_lld_busy()
Actual initializations are done in another patch (PATCH 2).
Below is a brief summary of how request-based dm behaves, including:
- making request from bio
- cloning, mapping and dispatching request
- completing request and bio
- suspending md
- resuming md
bio to request
==============
md->queue->make_request_fn() (dm_make_request()) calls __make_request()
for a bio submitted to the md.
Then, the bio is kept in the queue as a new request or merged into
another request in the queue if possible.
Cloning and Mapping
===================
Cloning and mapping are done in md->queue->request_fn() (dm_request_fn()),
when requests are dispatched after they are sorted by the I/O scheduler.
dm_request_fn() checks busy state of underlying devices using
target's busy() function and stops dispatching requests to keep them
on the dm device's queue if busy.
It helps better I/O merging, since no merge is done for a request
once it is dispatched to underlying devices.
Actual cloning and mapping are done in dm_prep_fn() and map_request()
called from dm_request_fn().
dm_prep_fn() clones not only request but also bios of the request
so that dm can hold bio completion in error cases and prevent
the bio submitter from noticing the error.
(See the "Completion" section below for details.)
After the cloning, the clone is mapped by target's map_rq() function
and inserted to underlying device's queue using
blk_insert_cloned_request().
Completion
==========
Request completion can be hooked by rq->end_io(), but then, all bios
in the request will have been completed even error cases, and the bio
submitter will have noticed the error.
To prevent the bio completion in error cases, request-based dm clones
both bio and request and hooks both bio->bi_end_io() and rq->end_io():
bio->bi_end_io(): end_clone_bio()
rq->end_io(): end_clone_request()
Summary of the request completion flow is below:
blk_end_request() for a clone request
=> blk_update_request()
=> bio->bi_end_io() == end_clone_bio() for each clone bio
=> Free the clone bio
=> Success: Complete the original bio (blk_update_request())
Error: Don't complete the original bio
=> blk_finish_request()
=> rq->end_io() == end_clone_request()
=> blk_complete_request()
=> dm_softirq_done()
=> Free the clone request
=> Success: Complete the original request (blk_end_request())
Error: Requeue the original request
end_clone_bio() completes the original request on the size of
the original bio in successful cases.
Even if all bios in the original request are completed by that
completion, the original request must not be completed yet to keep
the ordering of request completion for the stacking.
So end_clone_bio() uses blk_update_request() instead of
blk_end_request().
In error cases, end_clone_bio() doesn't complete the original bio.
It just frees the cloned bio and gives over the error handling to
end_clone_request().
end_clone_request(), which is called with queue lock held, completes
the clone request and the original request in a softirq context
(dm_softirq_done()), which has no queue lock, to avoid a deadlock
issue on submission of another request during the completion:
- The submitted request may be mapped to the same device
- Request submission requires queue lock, but the queue lock
has been held by itself and it doesn't know that
The clone request has no clone bio when dm_softirq_done() is called.
So target drivers can't resubmit it again even error cases.
Instead, they can ask dm core for requeueing and remapping
the original request in that cases.
suspend
=======
Request-based dm uses stopping md->queue as suspend of the md.
For noflush suspend, just stops md->queue.
For flush suspend, inserts a marker request to the tail of md->queue.
And dispatches all requests in md->queue until the marker comes to
the front of md->queue. Then, stops dispatching request and waits
for the all dispatched requests to complete.
After that, completes the marker request, stops md->queue and
wake up the waiter on the suspend queue, md->wait.
resume
======
Starts md->queue.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Currently, device-mapper maintains a separate instance of 'struct
queue_limits' for each table of each device. When the configuration of
a device is to be changed, first its table is loaded and this structure
is populated, then the device is 'resumed' and the calculated
queue_limits are applied.
This places restrictions on how userspace may process related devices,
where it is often advantageous to 'load' tables for several devices
at once before 'resuming' them together. As the new queue_limits
only take effect after the 'resume', if they are changing and one
device uses another, the latter must be 'resumed' before the former
may be 'loaded'.
This patch moves the calculation of these queue_limits out of
the 'load' operation into 'resume'. Since we are no longer
pre-calculating this struct, we no longer need to maintain copies
within our dm structs.
dm_set_device_limits() now passes the 'start' of the device's
data area (aka pe_start) as the 'offset' to blk_stack_limits().
init_valid_queue_limits() is replaced by blk_set_default_limits().
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: martin.petersen@oracle.com
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Add support for passing a 32 bit "cookie" into the kernel with the
DM_SUSPEND, DM_DEV_RENAME and DM_DEV_REMOVE ioctls. The (unsigned)
value of this cookie is returned to userspace alongside the uevents
issued by these ioctls in the variable DM_COOKIE.
This means the userspace process issuing these ioctls can be notified
by udev after udev has completed any actions triggered.
To minimise the interface extension, we pass the cookie into the
kernel in the event_nr field which is otherwise unused when calling
these ioctls. Incrementing the version number allows userspace to
determine in advance whether or not the kernel supports the cookie.
If the kernel does support this but userspace does not, there should
be no impact as the new variable will just get ignored.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Pass empty barrier flushes to the targets in dm_flush().
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Introduce num_flush_requests for a target to set to say how many flush
instructions (empty barriers) it wants to receive. These are sent by
__clone_and_map_empty_barrier with map_info->flush_request going from 0
to (num_flush_requests - 1).
Old targets without flush support won't receive any flush requests.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Remove the check that the size of the cloned bio is not zero because a
subsequent patch needs to send zero-sized barriers down this path.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
If the underlying device doesn't support barriers and dm receives a
barrier, it waits until all requests on that device drain so it no
longer needs to report -EOPNOTSUPP to the caller.
This patch deals with the confusing situation when moving a volume from
one physical device to another triggers an EOPNOTSUPP on a volume that
didn't report it before.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
With the following patches, more than one error can occur during
processing. Change md->barrier_error so that only the first one is
recorded and returned to the caller.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
If barrier request was returned with DM_ENDIO_REQUEUE,
requeue it in dm_wq_work instead of dec_pending.
This allows us to correctly handle a situation when some targets
are asking for a requeue and other targets signal an error.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Make dm_flush return void.
The first error during flush is stored in md->barrier_error instead.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Fix a potential deadlock when creating multiple snapshots by holding a
reference to struct block_device for the whole lifecycle of every dm
device instead of obtaining it independently at each point it is needed.
bdget_disk() was called while the device was being suspended, in
dm_suspend(). However there could be other devices already suspended,
for example when creating additional snapshots of a device. bdget_disk()
can wait for IO and allocate memory resulting in waiting for the
already-suspended device - deadlock.
This patch changes the code so that it gets the reference to struct
block_device when struct mapped_device is allocated and initialized in
alloc_dev() where it is always OK to allocate memory or wait for I/O.
It drops the reference when it is destroyed in free_dev(). Thus there
is no call to bdget_disk() while any device is suspended.
Previously unlock_fs() was called only if bdev was held. Now it is
called unconditionally, but the superfluous calls are harmless because
it returns immediately if the filesystem was not previously frozen.
This patch also now allows the device size to be changed in a
noflush suspend because the bdev is held. This has no adverse effect.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Rename suspended_bdev to bdev.
This patch doesn't change any functionality, just renames the variable.
In the next patch, the variable will be used even for non-suspended device.
(Pre-requisite for the per-target barrier support patches.)
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
A bio that has two or more vector entries, size less than or equal to
page size, that crosses a stripe boundary of an underlying md device is
accepted by device mapper (it conforms to all its limits) but not by the
underlying device.
The fix is: If device mapper selects the one-page maximum request size,
it also needs to set its own q->merge_bvec_fn to reject any bios with
multiple vector entries that span more pages.
The problem was discovered in the following scenario:
* MD - RAID-0
* LV on the top of it (raid1, snapshot or striped with chunk
size/stripe larger than RAID-0 stripe)
* one of the logical volumes is exported to xen domU
* inside xen domU it is partitioned, the key point is that the partition
must be unaligned on page boundary (fdisk normally aligns the partition to
63 sectors which will trigger it)
* install the system on the partitioned disk in domU
This causes I/O failures in dom0.
Reference: https://bugzilla.redhat.com/show_bug.cgi?id=223947
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Do not process sysfs attributes when device is being destroyed.
Otherwise code can cause
BUG_ON(test_bit(DMF_FREEING, &md->flags));
in dm_put() call.
Cc: stable@kernel.org
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
When porting blktrace to tracepoints, we changed to trace/block.h
for trace prober declarations.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
TRACE_EVENT is a more generic way to define tracepoints. Doing so adds
these new capabilities to this tracepoint:
- zero-copy and per-cpu splice() tracing
- binary tracing without printf overhead
- structured logging records exposed under /debug/tracing/events
- trace events embedded in function tracer output and other plugins
- user-defined, per tracepoint filter expressions
...
Cons:
- no dev_t info for the output of plug, unplug_timer and unplug_io events.
no dev_t info for getrq and sleeprq events if bio == NULL.
no dev_t info for rq_abort,...,rq_requeue events if rq->rq_disk == NULL.
This is mainly because we can't get the deivce from a request queue.
But this may change in the future.
- A packet command is converted to a string in TP_assign, not TP_print.
While blktrace do the convertion just before output.
Since pc requests should be rather rare, this is not a big issue.
- In blktrace, an event can have 2 different print formats, but a TRACE_EVENT
has a unique format, which means we have some unused data in a trace entry.
The overhead is minimized by using __dynamic_array() instead of __array().
I've benchmarked the ioctl blktrace vs the splice based TRACE_EVENT tracing:
dd dd + ioctl blktrace dd + TRACE_EVENT (splice)
1 7.36s, 42.7 MB/s 7.50s, 42.0 MB/s 7.41s, 42.5 MB/s
2 7.43s, 42.3 MB/s 7.48s, 42.1 MB/s 7.43s, 42.4 MB/s
3 7.38s, 42.6 MB/s 7.45s, 42.2 MB/s 7.41s, 42.5 MB/s
So the overhead of tracing is very small, and no regression when using
those trace events vs blktrace.
And the binary output of TRACE_EVENT is much smaller than blktrace:
# ls -l -h
-rw-r--r-- 1 root root 8.8M 06-09 13:24 sda.blktrace.0
-rw-r--r-- 1 root root 195K 06-09 13:24 sda.blktrace.1
-rw-r--r-- 1 root root 2.7M 06-09 13:25 trace_splice.out
Following are some comparisons between TRACE_EVENT and blktrace:
plug:
kjournald-480 [000] 303.084981: block_plug: [kjournald]
kjournald-480 [000] 303.084981: 8,0 P N [kjournald]
unplug_io:
kblockd/0-118 [000] 300.052973: block_unplug_io: [kblockd/0] 1
kblockd/0-118 [000] 300.052974: 8,0 U N [kblockd/0] 1
remap:
kjournald-480 [000] 303.085042: block_remap: 8,0 W 102736992 + 8 <- (8,8) 33384
kjournald-480 [000] 303.085043: 8,0 A W 102736992 + 8 <- (8,8) 33384
bio_backmerge:
kjournald-480 [000] 303.085086: block_bio_backmerge: 8,0 W 102737032 + 8 [kjournald]
kjournald-480 [000] 303.085086: 8,0 M W 102737032 + 8 [kjournald]
getrq:
kjournald-480 [000] 303.084974: block_getrq: 8,0 W 102736984 + 8 [kjournald]
kjournald-480 [000] 303.084975: 8,0 G W 102736984 + 8 [kjournald]
bash-2066 [001] 1072.953770: 8,0 G N [bash]
bash-2066 [001] 1072.953773: block_getrq: 0,0 N 0 + 0 [bash]
rq_complete:
konsole-2065 [001] 300.053184: block_rq_complete: 8,0 W () 103669040 + 16 [0]
konsole-2065 [001] 300.053191: 8,0 C W 103669040 + 16 [0]
ksoftirqd/1-7 [001] 1072.953811: 8,0 C N (5a 00 08 00 00 00 00 00 24 00) [0]
ksoftirqd/1-7 [001] 1072.953813: block_rq_complete: 0,0 N (5a 00 08 00 00 00 00 00 24 00) 0 + 0 [0]
rq_insert:
kjournald-480 [000] 303.084985: block_rq_insert: 8,0 W 0 () 102736984 + 8 [kjournald]
kjournald-480 [000] 303.084986: 8,0 I W 102736984 + 8 [kjournald]
Changelog from v2 -> v3:
- use the newly introduced __dynamic_array().
Changelog from v1 -> v2:
- use __string() instead of __array() to minimize the memory required
to store hex dump of rq->cmd().
- support large pc requests.
- add missing blk_fill_rwbs_rq() in block_rq_requeue TRACE_EVENT.
- some cleanups.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A2DF669.5070905@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Merge reason: tracing/core was on a .30-rc1 base and was missing out on
on a handful of tracing fixes present in .30-rc5-almost.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It's used by DM and MD and generally useful, so move the bio list
helpers into bio.h.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Barriers are submitted to a worker thread that issues them in-order.
The thread is modified so that when it sees a barrier request it waits
for all pending IO before the request then submits the barrier and
waits for it. (We must wait, otherwise it could be intermixed with
following requests.)
Errors from the barrier request are recorded in a per-device barrier_error
variable. There may be only one barrier request in progress at once.
For now, the barrier request is converted to a non-barrier request when
sending it to the underlying device.
This patch guarantees correct barrier behavior if the underlying device
doesn't perform write-back caching. The same requirement existed before
barriers were supported in dm.
Bottom layer barrier support (sending barriers by target drivers) and
handling devices with write-back caches will be done in further patches.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Remove queue_io return value and a loop in dm_request.
IO may be submitted to a worker thread with queue_io(). queue_io() sets
DMF_QUEUE_IO_TO_THREAD so that all further IO is queued for the thread. When
the thread finishes its work, it clears DMF_QUEUE_IO_TO_THREAD and from this
point on, requests are submitted from dm_request again. This will be used
for processing barriers.
Remove the loop in dm_request. queue_io() can submit I/Os to the worker thread
even if DMF_QUEUE_IO_TO_THREAD was not set.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Rework shutting down on suspend and document the associated rules.
Drop write lock in __split_and_process_bio to allow more processing
concurrency.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Refactor the code in dm_request().
Require the new DMF_BLOCK_FOR_SUSPEND flag on readahead bios we will
discard so we don't drop such bios while processing a barrier.
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Split the DMF_BLOCK_IO flag into two.
DMF_BLOCK_IO_FOR_SUSPEND is set when I/O must be blocked while suspending a
device. DMF_QUEUE_IO_TO_THREAD is set when I/O must be queued to a
worker thread for later processing.
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Prepare for full barrier implementation: first remove the restricted support.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This patch provides support for data integrity passthrough in the device
mapper.
- If one or more component devices support integrity an integrity
profile is preallocated for the DM device.
- If all component devices have compatible profiles the DM device is
flagged as capable.
- Handle integrity metadata when splitting and cloning bios.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Set queue ordered mode. It doesn't really matter what we set here
because we don't ever put any requests on the queue. But we need to set
something other than QUEUE_ORDERED_NONE so that __generic_make_request
passes barrier requests to us.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Move wait queue declaration and unplug to dm_wait_for_completion.
The purpose is to minimize duplicate code in the further patches.
The patch reorders functions a little bit. It doesn't change any
functionality. For proper non-deadlock operation, add_wait_queue must
happen before set_current_state(interruptible) and before the test for
!atomic_read(&md->pending).
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Merge pushback and deferred lists into one list - use deferred list
for both deferred and pushed-back bios.
This will be needed for proper support of barrier bios: it is impossible to
support ordering correctly with two lists because the requests on both lists
will be mixed up.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Allow uninterruptible wait for pending IOs.
Add argument "interruptible" to dm_wait_for_completion that specifies
either interruptible or uninterruptible waiting.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Merge __flush_deferred_io() into the only caller, dm_wq_work().
There's no need to have a function that has only one caller.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Move the bio_io_error() calls directly into __split_and_process_bio().
This avoids some code duplication in later patches.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Rename __split_bio() to __split_and_process_bio() because it not only splits
the bio to serveral parts, but also submits them to target drivers.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Remove struct dm_wq_req and move "work" directly into struct mapped_device.
In the revised implementation, the thread will do just one type of work
(processing the queue).
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Remove the context field from struct dm_wq_req because we will no longer
need it.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Remove "type" field from struct dm_wq_req because we no longer need it
to have more than one value.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
The following oops has been reported when dm-crypt runs over a loop device.
...
[ 70.381058] Process loop0 (pid: 4268, ti=cf3b2000 task=cf1cc1f0 task.ti=cf3b2000)
...
[ 70.381058] Call Trace:
[ 70.381058] [<d0d76601>] ? crypt_dec_pending+0x5e/0x62 [dm_crypt]
[ 70.381058] [<d0d767b8>] ? crypt_endio+0xa2/0xaa [dm_crypt]
[ 70.381058] [<d0d76716>] ? crypt_endio+0x0/0xaa [dm_crypt]
[ 70.381058] [<c01a2f24>] ? bio_endio+0x2b/0x2e
[ 70.381058] [<d0806530>] ? dec_pending+0x224/0x23b [dm_mod]
[ 70.381058] [<d08066e4>] ? clone_endio+0x79/0xa4 [dm_mod]
[ 70.381058] [<d080666b>] ? clone_endio+0x0/0xa4 [dm_mod]
[ 70.381058] [<c01a2f24>] ? bio_endio+0x2b/0x2e
[ 70.381058] [<c02bad86>] ? loop_thread+0x380/0x3b7
[ 70.381058] [<c02ba8a1>] ? do_lo_send_aops+0x0/0x165
[ 70.381058] [<c013754f>] ? autoremove_wake_function+0x0/0x33
[ 70.381058] [<c02baa06>] ? loop_thread+0x0/0x3b7
When a table is being replaced, it waits for I/O to complete
before destroying the mempool, but the endio function doesn't
call mempool_free() until after completing the bio.
Fix it by swapping the order of those two operations.
The same problem occurs in dm.c with md referenced after dec_pending.
Again, we swap the order.
Cc: stable@kernel.org
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Implement simple read-only sysfs entry for device-mapper block device.
This patch adds a simple sysfs directory named "dm" under block device
properties and implements
- name attribute (string containing mapped device name)
- uuid attribute (string containing UUID, or empty string if not set)
The kobject is embedded in mapped_device struct, so no additional
memory allocation is needed for initializing sysfs entry.
During the processing of sysfs attribute we need to lock mapped device
which is done by a new function dm_get_from_kobj, which returns the md
associated with kobject and increases the usage count.
Each 'show attribute' function is responsible for its own locking.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Rework table reference counting.
The existing code uses a reference counter. When the last reference is
dropped and the counter reaches zero, the table destructor is called.
Table reference counters are acquired/released from upcalls from other
kernel code (dm_any_congested, dm_merge_bvec, dm_unplug_all).
If the reference counter reaches zero in one of the upcalls, the table
destructor is called from almost random kernel code.
This leads to various problems:
* dm_any_congested being called under a spinlock, which calls the
destructor, which calls some sleeping function.
* the destructor attempting to take a lock that is already taken by the
same process.
* stale reference from some other kernel code keeps the table
constructed, which keeps some devices open, even after successful
return from "dmsetup remove". This can confuse lvm and prevent closing
of underlying devices or reusing device minor numbers.
The patch changes reference counting so that the table destructor can be
called only at predetermined places.
The table has always exactly one reference from either mapped_device->map
or hash_cell->new_map. After this patch, this reference is not counted
in table->holders. A pair of dm_create_table/dm_destroy_table functions
is used for table creation/destruction.
Temporary references from the other code increase table->holders. A pair
of dm_table_get/dm_table_put functions is used to manipulate it.
When the table is about to be destroyed, we wait for table->holders to
reach 0. Then, we call the table destructor. We use active waiting with
msleep(1), because the situation happens rarely (to one user in 5 years)
and removing the device isn't performance-critical task: the user doesn't
care if it takes one tick more or not.
This way, the destructor is called only at specific points
(dm_table_destroy function) and the above problems associated with lazy
destruction can't happen.
Finally remove the temporary protection added to dm_any_congested().
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Implement barrier support for single device DM devices
This patch implements barrier support in DM for the common case of dm linear
just remapping a single underlying device. In this case we can safely
pass the barrier through because there can be no reordering between
devices.
NB. Any DM device might cease to support barriers if it gets
reconfigured so code must continue to allow for a possible
-EOPNOTSUPP on every barrier bio submitted. - agk
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Move one dm_table_put() so that the last reference in the thread
gets dropped in __unbind().
This is required for a following patch,
dm-table-rework-reference-counting.patch, which will change the logic in
such a way that table destructor is called only at specific points in
the code.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Instead of having a global bio slab cache, add a reference to one
in each bio_set that is created. This allows for personalized slabs
in each bio_set, so that they can have bios of different sizes.
This means we can personalize the bios we return. File systems may
want to embed the bio inside another structure, to avoid allocation
more items (and stuffing them in ->bi_private) after the get a bio.
Or we may want to embed a number of bio_vecs directly at the end
of a bio, to avoid doing two allocations to return a bio. This is now
possible.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Port to the new tracepoints API: split DEFINE_TRACE() and DECLARE_TRACE()
sites. Spread them out to the usage sites, as suggested by
Mathieu Desnoyers.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
This was a forward port of work done by Mathieu Desnoyers, I changed it to
encode the 'what' parameter on the tracepoint name, so that one can register
interest in specific events and not on classes of events to then check the
'what' parameter.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
dm_any_congested() just checks for the DMF_BLOCK_IO and has no
code to make sure that suspend waits for dm_any_congested() to
complete. This patch adds such a check.
Without it, a race can occur with dm_table_put() attempting to
destroying the table in the wrong thread, the one running
dm_any_congested() which is meant to be quick and return
immediately.
Two examples of problems:
1. Sleeping functions called from congested code, the caller
of which holds a spin lock.
2. An ABBA deadlock between pdflush and multipathd. The two locks
in contention are inode lock and kernel lock.
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This doesn't fix any bug, just moves wake_up immediately after decrementing
md->pending, for better code readability.
It must be clear to anyone manipulating md->pending to wake up
the queue if md->pending reaches zero, so move the wakeup as close to
the decrementing as possible.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* git://git.kernel.org/pub/scm/linux/kernel/git/viro/bdev: (66 commits)
[PATCH] kill the rest of struct file propagation in block ioctls
[PATCH] get rid of struct file use in blkdev_ioctl() BLKBSZSET
[PATCH] get rid of blkdev_locked_ioctl()
[PATCH] get rid of blkdev_driver_ioctl()
[PATCH] sanitize blkdev_get() and friends
[PATCH] remember mode of reiserfs journal
[PATCH] propagate mode through swsusp_close()
[PATCH] propagate mode through open_bdev_excl/close_bdev_excl
[PATCH] pass fmode_t to blkdev_put()
[PATCH] kill the unused bsize on the send side of /dev/loop
[PATCH] trim file propagation in block/compat_ioctl.c
[PATCH] end of methods switch: remove the old ones
[PATCH] switch sr
[PATCH] switch sd
[PATCH] switch ide-scsi
[PATCH] switch tape_block
[PATCH] switch dcssblk
[PATCH] switch dasd
[PATCH] switch mtd_blkdevs
[PATCH] switch mmc
...
This patch tidies local_init() in preparation for request-based dm.
No functional change.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This patch removes the DM_WQ_FLUSH_ALL state that is unnecessary.
The dm_queue_flush(md, DM_WQ_FLUSH_ALL, NULL) in dm_suspend()
is never invoked because:
- 'goto flush_and_out' is the same as 'goto out' because
the 'goto flush_and_out' is called only when '!noflush'
- If r is non-zero, then the code above will invoke 'goto out'
and skip this code.
No functional change.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
When a bio gets split, mark its fragments with the BIO_CLONED flag.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
To keep the size of changesets sane we split the switch by drivers;
to keep the damn thing bisectable we do the following:
1) rename the affected methods, add ones with correct
prototypes, make (few) callers handle both. That's this changeset.
2) for each driver convert to new methods. *ALL* drivers
are converted in this series.
3) kill the old (renamed) methods.
Note that it _is_ a flagday; all in-tree drivers are converted and by the
end of this series no trace of old methods remain. The only reason why
we do that this way is to keep the damn thing bisectable and allow per-driver
debugging if anything goes wrong.
New methods:
open(bdev, mode)
release(disk, mode)
ioctl(bdev, mode, cmd, arg) /* Called without BKL */
compat_ioctl(bdev, mode, cmd, arg)
locked_ioctl(bdev, mode, cmd, arg) /* Called with BKL, legacy */
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Move stats related fields - stamp, in_flight, dkstats - from disk to
part0 and unify stat handling such that...
* part_stat_*() now updates part0 together if the specified partition
is not part0. ie. part_stat_*() are now essentially all_stat_*().
* {disk|all}_stat_*() are gone.
* part_round_stats() is updated similary. It handles part0 stats
automatically and disk_round_stats() is killed.
* part_{inc|dec}_in_fligh() is implemented which automatically updates
part0 stats for parts other than part0.
* disk_map_sector_rcu() is updated to return part0 if no part matches.
Combined with the above changes, this makes NULL special case
handling in callers unnecessary.
* Separate stats show code paths for disk are collapsed into part
stats show code paths.
* Rename disk_stat_lock/unlock() to part_stat_lock/unlock()
While at it, reposition stat handling macros a bit and add missing
parentheses around macro parameters.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Implement {disk|part}_to_dev() and use them to access generic device
instead of directly dereferencing {disk|part}->dev. To make sure no
user is left behind, rename generic devices fields to __dev.
This is in preparation of unifying partition 0 handling with other
partitions.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
There are two variants of stat functions - ones prefixed with double
underbars which don't care about preemption and ones without which
disable preemption before manipulating per-cpu counters. It's unclear
whether the underbarred ones assume that preemtion is disabled on
entry as some callers don't do that.
This patch unifies diskstats access by implementing disk_stat_lock()
and disk_stat_unlock() which take care of both RCU (for partition
access) and preemption (for per-cpu counter access). diskstats access
should always be enclosed between the two functions. As such, there's
no need for the versions which disables preemption. They're removed
and double underbars ones are renamed to drop the underbars. As an
extra argument is added, there's no danger of using the old version
unconverted.
disk_stat_lock() uses get_cpu() and returns the cpu index and all
diskstat functions which access per-cpu counters now has @cpu
argument to help RT.
This change adds RCU or preemption operations at some places but also
collapses several preemption ops into one at others. Overall, the
performance difference should be negligible as all involved ops are
very lightweight per-cpu ones.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
* Implement disk_devt() and part_devt() and use them to directly
access devt instead of computing it from ->major and ->first_minor.
Note that all references to ->major and ->first_minor outside of
block layer is used to determine devt of the disk (the part0) and as
->major and ->first_minor will continue to represent devt for the
disk, converting these users aren't strictly necessary. However,
convert them for consistency.
* Implement disk_max_parts() to avoid directly deferencing
genhd->minors.
* Update bdget_disk() such that it doesn't assume consecutive minor
space.
* Move devt computation from register_disk() to add_disk() and make it
the only one (all other usages use the initially determined value).
These changes clean up the code and will help disk->part dereference
fix and extended block device numbers.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
If for any reason dm_merge_bvec() is given an offset beyond the end of the
device, avoid an oops and always allow one page to be added to an empty bio.
We'll reject the I/O later after the bio is submitted.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Some callers assume they can always add at least one page to an empty bio,
so dm_merge_bvec should not return 0 in this case: we'll reject the I/O
later after the bio is submitted.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Introduce a bvec merge function for device mapper devices
for dynamic size restrictions.
This code ensures the requested biovec lies within a single
target and then calls a target-specific function to check
against any constraints imposed by underlying devices.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
The small patch below:
- Removes the unused md argument from both specific_minor() and next_free_minor()
- Folds kmalloc + memset(0) into a single kzalloc call in alloc_dev()
This has been compile tested on x86.
Signed-off-by: Frederik Deweerdt <frederik.deweerdt@gmail.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Remove client counting code that is no longer needed.
Initialization and destruction is made globally from dm_init and dm_exit and is
not based on client counts. Initialization allocates only one empty slab cache,
so there is no negative impact from performing the initialization always,
regardless of whether some client uses kcopyd or not.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Add a single-thread workqueue for each mapped device
and move flushing of the lists of pushback and deferred bios
to this new workqueue.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Change io_locking to allow processing flush in separate thread.
Because we have DMF_BLOCK_IO already set, any possible
new ios are queued in dm_requests now.
In the case of interrupting previous wait there can be more
ios queued (we unlocked io_lock for a while) but this is safe.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Tidy dm_suspend function
- change return value logic in dm_suspend
- use atomic_read only once.
- move DMF_BLOCK_IO clearing into one place
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Refactor deferred bio_list processing.
- use separate _merge_pushback_list function
- move deferred bio list pick up to flush function
- use bio_list_pop instead of bio_list_get
- simplify noflush flag use
No real functional change in this patch.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Tidy labels in alloc_dev to make later patches more clear.
No functional change in this patch.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This moves the block devices to /sys/class/block. It will create a
flat list of all block devices, with the disks and partitions in one
directory. For compatibility /sys/block is created and contains symlinks
to the disks.
/sys/class/block
|-- sda -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda
|-- sda1 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda1
|-- sda10 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda10
|-- sda5 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda5
|-- sda6 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda6
|-- sda7 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda7
|-- sda8 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda8
|-- sda9 -> ../../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda/sda9
`-- sr0 -> ../../devices/pci0000:00/0000:00:1f.2/host1/target1:0:0/1:0:0:0/block/sr0
/sys/block/
|-- sda -> ../devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/block/sda
`-- sr0 -> ../devices/pci0000:00/0000:00:1f.2/host1/target1:0:0/1:0:0:0/block/sr0
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Insert a missing KOBJ_CHANGE notification when a device is renamed.
Cc: Scott James Remnant <scott@ubuntu.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This patch fixes a panic on shrinking a DM device if there is
outstanding I/O to the part of the device that is being removed.
(Normally this doesn't happen - a filesystem would be resized first,
for example.)
The bug is that __clone_and_map() assumes dm_table_find_target()
always returns a valid pointer. It may fail if a bio arrives from the
block layer but its target sector is no longer included in the DM
btree.
This patch appends an empty entry to table->targets[] which will
be returned by a lookup beyond the end of the device.
After calling dm_table_find_target(), __clone_and_map() and target_message()
check for this condition using
dm_target_is_valid().
Sample test script to trigger oops:
This patch adds support for the dm_path_event dm_send_event functions which
create and send udev events.
Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This patch adds a uevent skeleton to device-mapper.
Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Use bio_io_error() in only two places and tidy the code,
preparing for later patches.
There is no functional change in this patch.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This patch fixes a bd_mount_sem counter corruption bug in device-mapper.
thaw_bdev() should be called only when freeze_bdev() was called for the
device.
Otherwise, thaw_bdev() will up bd_mount_sem and corrupt the semaphore counter.
struct block_device with the corrupted semaphore may remain in slab cache
and be reused later.
Attached patch will fix it by calling unlock_fs() instead.
unlock_fs() will determine whether it should call thaw_bdev()
by checking the device is frozen or not.
Easy reproducer is:
#!/bin/sh
while [ 1 ]; do
dmsetup --notable create a
dmsetup --nolockfs suspend a
dmsetup remove a
done
It's not easy to see the effect of corrupted semaphore.
So I have tested with putting printk below in bdev_alloc_inode():
if (atomic_read(&ei->bdev.bd_mount_sem.count) != 1)
printk(KERN_DEBUG "Incorrect semaphore count = %d (%p)\n",
atomic_read(&ei->bdev.bd_mount_sem.count),
&ei->bdev);
Without the patch, I saw something like:
Incorrect semaphore count = 17 (f2ab91c0)
With the patch, the message didn't appear.
The bug was introduced in 2.6.16 with this bug fix:
commit d9dde59ba0
Date: Fri Feb 24 13:04:24 2006 -0800
[PATCH] dm: missing bdput/thaw_bdev at removal
Need to unfreeze and release bdev otherwise the bdev inode with
inconsistent state is reused later and cause problem.
and backported to 2.6.15.5.
It occurs only in free_dev(), which is called only when the dm device is
removed. The buggy code is executed only if md->suspended_bdev is
non-NULL and that can happen only when the device was suspended without
noflush.
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: stable@kernel.org
As bi_end_io is only called once when the reqeust is complete,
the 'size' argument is now redundant. Remove it.
Now there is no need for bio_endio to subtract the size completed
from bi_size. So don't do that either.
While we are at it, change bi_end_io to return void.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This patch provides more information concerning REMAP operations on block
IOs. The additional information provides clearer details at the user level,
and supports post-processing analysis in btt.
o Adds in partition remaps on the same device.
o Fixed up the remap information in DM to be in the right order
o Sent up mapped-from and mapped-to device information
Signed-off-by: Alan D. Brunelle <alan.brunelle@hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Some of the code has been gradually transitioned to using the proper
struct request_queue, but there's lots left. So do a full sweet of
the kernel and get rid of this typedef and replace its uses with
the proper type.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
No need to warn unregister_blkdev() failure by the callers. (The previous
patch makes unregister_blkdev() print error message in error case)
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch causes device-mapper to reject any barrier requests. This is done
since most of the targets won't handle this correctly anyway. So until the
situation improves it is better to reject these requests at the first place.
Since barrier requests won't get to the targets, the checks there can be
removed.
Cc: stable@kernel.org
Signed-off-by: Stefan Bader <shbader@de.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use new KMEM_CACHE() macro and make the newly-exposed structure names more
meaningful. Also remove some superfluous casts and inlines (let a modern
compiler be the judge).
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Make the mapped device structure accessible to hardware handlers so error
messages can include the device name.
Signed-off-by: Edward Goggin <egoggin@emc.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently we scale the mempool sizes depending on memory installed
in the machine, except for the bio pool itself which sits at a fixed
256 entry pre-allocation.
There's really no point in "optimizing" this OOM path, we just need
enough preallocated to make progress. A single unit is enough, lets
scale it down to 2 just to be on the safe side.
This patch saves ~150kb of pinned kernel memory on a 32-bit box.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Allow noflush suspend/resume of device-mapper device only for the case
where the device size is unchanged.
Otherwise, dm-multipath devices can stall when resumed if noflush was used
when suspending them, all paths have failed and queue_if_no_path is set.
Explanation:
1. Something is doing fsync() on the block dev,
holding inode->i_sem
2. The fsync write is blocked by all-paths-down and queue_if_no_path
3. Someone requests to suspend the dm device with noflush.
Pending writes are left in queue.
4. In the middle of dm_resume(), __bind() tries to get
inode->i_sem to do __set_size() and waits forever.
'noflush suspend' is a new device-mapper feature introduced in
early 2.6.20. So I hope the fix being included before 2.6.20 is
released.
Example of reproducer:
1. Create a multipath device by dmsetup
2. Fail all paths during mkfs
3. Do dmsetup suspend --noflush and load new map with healthy paths
4. Do dmsetup resume
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Acked-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In device-mapper I/O is sometimes queued within targets for later processing.
For example the multipath target can be configured to store I/O when no paths
are available instead of returning it -EIO.
This patch allows the device-mapper core to instruct a target to transfer the
contents of any such in-target queue back into the core. This frees up the
resources used by the target so the core can replace that target with an
alternative one and then resend the I/O to it. Without this patch the only
way to change the target in such circumstances involves returning the I/O with
an error back to the filesystem/application. In the multipath case, this
patch will let us add new paths for existing I/O to try after all the existing
paths have failed.
DMF_NOFLUSH_SUSPENDING
----------------------
If the DM_NOFLUSH_FLAG ioctl option is specified at suspend time, the
DMF_NOFLUSH_SUSPENDING flag is set in md->flags during dm_suspend(). It
is always cleared before dm_suspend() returns.
The flag must be visible while the target is flushing pending I/Os so it
is set before presuspend where the flush starts and unset after the wait
for md->pending where the flush ends.
Target drivers can check this flag by calling dm_noflush_suspending().
DM_MAPIO_REQUEUE / DM_ENDIO_REQUEUE
-----------------------------------
A target's map() function can now return DM_MAPIO_REQUEUE to request the
device mapper core queue the bio.
Similarly, a target's end_io() function can return DM_ENDIO_REQUEUE to request
the same. This has been labelled 'pushback'.
The __map_bio() and clone_endio() functions in the core treat these return
values as errors and call dec_pending() to end the I/O.
dec_pending
-----------
dec_pending() saves the pushback request in struct dm_io->error. Once all
the split clones have ended, dec_pending() will put the original bio on
the md->pushback list. Note that this supercedes any I/O errors.
It is possible for the suspend with DM_NOFLUSH_FLAG to be aborted while
in progress (e.g. by user interrupt). dec_pending() checks for this and
returns -EIO if it happened.
pushdback list and pushback_lock
--------------------------------
The bio is queued on md->pushback temporarily in dec_pending(), and after
all pending I/Os return, md->pushback is merged into md->deferred in
dm_suspend() for re-issuing at resume time.
md->pushback_lock protects md->pushback.
The lock should be held with irq disabled because dec_pending() can be
called from interrupt context.
Queueing bios to md->pushback in dec_pending() must be done atomically
with the check for DMF_NOFLUSH_SUSPENDING flag. So md->pushback_lock is
held when checking the flag. Otherwise dec_pending() may queue a bio to
md->pushback after the interrupted dm_suspend() flushes md->pushback.
Then the bio would be left in md->pushback.
Flag setting in dm_suspend() can be done without md->pushback_lock because
the flag is checked only after presuspend and the set value is already
made visible via the target's presuspend function.
The flag can be checked without md->pushback_lock (e.g. the first part of
the dec_pending() or target drivers), because the flag is checked again
with md->pushback_lock held when the bio is really queued to md->pushback
as described above. So even if the flag is cleared after the lockless
checkings, the bio isn't left in md->pushback but returned to applications
with -EIO.
Other notes on the current patch
--------------------------------
- md->pushback is added to the struct mapped_device instead of using
md->deferred directly because md->io_lock which protects md->deferred is
rw_semaphore and can't be used in interrupt context like dec_pending(),
and md->io_lock protects the DMF_BLOCK_IO flag of md->flags too.
- Don't issue lock_fs() in dm_suspend() if the DM_NOFLUSH_FLAG
ioctl option is specified, because I/Os generated by lock_fs() would be
pushed back and never return if there were no valid devices.
- If an error occurs in dm_suspend() after the DMF_NOFLUSH_SUSPENDING
flag is set, md->pushback must be flushed because I/Os may be queued to
the list already. (flush_and_out label in dm_suspend())
Test results
------------
I have tested using multipath target with the next patch.
The following tests are for regression/compatibility:
- I/Os succeed when valid paths exist;
- I/Os fail when there are no valid paths and queue_if_no_path is not
set;
- I/Os are queued in the multipath target when there are no valid paths and
queue_if_no_path is set;
- The queued I/Os above fail when suspend is issued without the
DM_NOFLUSH_FLAG ioctl option. I/Os spanning 2 multipath targets also
fail.
The following tests are for the normal code path of new pushback feature:
- Queued I/Os in the multipath target are flushed from the target
but don't return when suspend is issued with the DM_NOFLUSH_FLAG
ioctl option;
- The I/Os above are queued in the multipath target again when
resume is issued without path recovery;
- The I/Os above succeed when resume is issued after path recovery
or table load;
- Queued I/Os in the multipath target succeed when resume is issued
with the DM_NOFLUSH_FLAG ioctl option after table load. I/Os
spanning 2 multipath targets also succeed.
The following tests are for the error paths of the new pushback feature:
- When the bdget_disk() fails in dm_suspend(), the
DMF_NOFLUSH_SUSPENDING flag is cleared and I/Os already queued to the
pushback list are flushed properly.
- When suspend with the DM_NOFLUSH_FLAG ioctl option is interrupted,
o I/Os which had already been queued to the pushback list
at the time don't return, and are re-issued at resume time;
o I/Os which hadn't been returned at the time return with EIO.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Tighten the use of return values from the target map and end_io functions.
Values of 2 and above are now explictly reserved for future use. There are no
existing targets using such values.
The patch has no effect on existing behaviour.
o Reserve return values of 2 and above from target map functions.
Any positive value currently indicates "mapping complete", but all
existing drivers use the value 1. We now make that a requirement
so we can assign new meaning to higher values in future.
The new definition of return values from target map functions is:
< 0 : error
= 0 : The target will handle the io (DM_MAPIO_SUBMITTED).
= 1 : Mapping completed (DM_MAPIO_REMAPPED).
> 1 : Reserved (undefined). Previously this was the same as '= 1'.
o Reserve return values of 2 and above from target end_io functions
for similar reasons.
DM_ENDIO_INCOMPLETE is introduced for a return value of 1.
Test results:
I have tested by using the multipath target.
I/Os succeed when valid paths exist.
I/Os are queued in the multipath target when there are no valid paths and
queue_if_no_path is set.
I/Os fail when there are no valid paths and queue_if_no_path is not set.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Change the interface of dm_suspend() so that we can pass several options
without increasing the number of parameters. The existing 'do_lockfs' integer
parameter is replaced by a flag DM_SUSPEND_LOCKFS_FLAG.
There is no functional change to the code.
Test results:
I have tested 'dmsetup suspend' command with/without the '--nolockfs'
option and confirmed the do_lockfs value is correctly set.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Replace all uses of kmem_cache_t with struct kmem_cache.
The patch was generated using the following script:
#!/bin/sh
#
# Replace one string by another in all the kernel sources.
#
set -e
for file in `find * -name "*.c" -o -name "*.h"|xargs grep -l $1`; do
quilt add $file
sed -e "1,\$s/$1/$2/g" $file >/tmp/$$
mv /tmp/$$ $file
quilt refresh
done
The script was run like this
sh replace kmem_cache_t "struct kmem_cache"
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
If the device is already suspended, just return the error and skip the code
that would incorrectly wipe md->suspended_bdev.
(This isn't currently a problem because existing code avoids calling this
function if the device is already suspended.)
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: <dm-devel@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I found a problem within device-mapper that occurs in low-mem situations. It
was found using a mirror target but I think in theory it would hit any setup
that stacks device-mapper devices (like LVM on top of multipath).
Since device-mapper core uses the common fs_bioset in clone_bio(), and a
private, but still global, bio_set in split_bvec() it is possible that the
filesystem and the first level target successfully get bios but the lower
level target doesn't because there is no more memory and the pool was drained
by upper layers. So the remapping will be stuck forever. To solve this
device-mapper core needs to use a private bio_set for each device.
Signed-off-by: Stefan Bader <Stefan.Bader@de.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch adds a target preresume hook.
It is called before the targets are resumed and if it returns an error the
resume gets cancelled.
The crypt target will use this to indicate that it is unable to process I/O
because no encryption key has been supplied.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Kiyoshi Ueda