Split drop_inmem_pages from commit_inmem_pages for code readability,
and prepare for the following modification.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
In write_begin, if storage supports stable_page, we don't need to wait for
writeback to update its contents.
This patch introduces to use wait_for_stable_page instead of
wait_on_page_writeback.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
The sceanrio is:
1. create fully node blocks
2. flush node blocks
3. write inline_data for all the node blocks again
4. flush node blocks redundantly
So, this patch tries to flush inline_data when flushing node blocks.
Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Pull f2fs updates from Jaegeuk Kim:
"This series adds two ioctls to control cached data and fragmented
files. Most of the rest fixes missing error cases and bugs that we
have not covered so far. Summary:
Enhancements:
- support an ioctl to execute online file defragmentation
- support an ioctl to flush cached data
- speed up shrinking of extent_cache entries
- handle broken superblock
- refector dirty inode management infra
- revisit f2fs_map_blocks to handle more cases
- reduce global lock coverage
- add detecting user's idle time
Major bug fixes:
- fix data race condition on cached nat entries
- fix error cases of volatile and atomic writes"
* tag 'for-f2fs-4.5' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (87 commits)
f2fs: should unset atomic flag after successful commit
f2fs: fix wrong memory condition check
f2fs: monitor the number of background checkpoint
f2fs: detect idle time depending on user behavior
f2fs: introduce time and interval facility
f2fs: skip releasing nodes in chindless extent tree
f2fs: use atomic type for node count in extent tree
f2fs: recognize encrypted data in f2fs_fiemap
f2fs: clean up f2fs_balance_fs
f2fs: remove redundant calls
f2fs: avoid unnecessary f2fs_balance_fs calls
f2fs: check the page status filled from disk
f2fs: introduce __get_node_page to reuse common code
f2fs: check node id earily when readaheading node page
f2fs: read isize while holding i_mutex in fiemap
Revert "f2fs: check the node block address of newly allocated nid"
f2fs: cover more area with nat_tree_lock
f2fs: introduce max_file_blocks in sbi
f2fs crypto: check CONFIG_F2FS_FS_XATTR for encrypted symlink
f2fs: introduce zombie list for fast shrinking extent trees
...
Otherwise, we can get mismatched largest extent information.
One example is:
1. mount f2fs w/ extent_cache
2. make a small extent
3. umount
4. mount f2fs w/o extent_cache
5. update the largest extent
6. umount
7. mount f2fs w/ extent_cache
8. get the old extent made by #2
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Maintain regular/symlink inode which has dirty pages in global dirty list
and record their total dirty pages count like the way of handling directory
inode.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
remove_dirty_dir_inode will be renamed to remove_dirty_inode as a generic
function in following patch for removing directory/regular/symlink inode
in global dirty list.
Here rename ino management related functions for readability, also in
order to avoid name conflict.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
kmap() in page_follow_link_light() needed to go - allowing to hold
an arbitrary number of kmaps for long is a great way to deadlocking
the system.
new helper (inode_nohighmem(inode)) needs to be used for pagecache
symlinks inodes; done for all in-tree cases. page_follow_link_light()
instrumented to yell about anything missed.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
As comment says, we don't need to call f2fs_lock_op in write_inode to prevent
from producing dirty node pages all the time.
That happens only when there is not enough free sections and we can avoid that
by calling balance_fs in prior to that.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
In following call stack, if unfortunately we lose all chances to truncate
inode page in remove_inode_page, eventually we will add the nid allocated
previously into free nid cache, this nid is with NID_NEW status and with
NEW_ADDR in its blkaddr pointer:
- f2fs_create
- f2fs_add_link
- __f2fs_add_link
- init_inode_metadata
- new_inode_page
- new_node_page
- set_node_addr(, NEW_ADDR)
- f2fs_init_acl failed
- remove_inode_page failed
- handle_failed_inode
- remove_inode_page failed
- iput
- f2fs_evict_inode
- remove_inode_page failed
- alloc_nid_failed cache a nid with valid blkaddr: NEW_ADDR
This may not only cause resource leak of previous inode, but also may cause
incorrect use of the previous blkaddr which is located in NO.nid node entry
when this nid is reused by others.
This patch tries to add this inode to orphan list if we fail to truncate
inode, so that we can obtain a second chance to release it in orphan
recovery flow.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
According to commit 5f16f3225b ("ext4: atomically set inode->i_flags in
ext4_set_inode_flags()").
Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
If we clear inline data/dentry flag in handle_failed_inode, we will fail
to decline the stat count of inline data/dentry in f2fs_evict_inode due
to no flag in inode. So remove the wrong clearing.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
In handle_failed_inode, there is a potential deadlock which can happen
in below call path:
- f2fs_create
- f2fs_lock_op down_read(cp_rwsem)
- f2fs_add_link
- __f2fs_add_link
- init_inode_metadata
- f2fs_init_security failed
- truncate_blocks failed
- handle_failed_inode
- f2fs_truncate
- truncate_blocks(..,true)
- write_checkpoint
- block_operations
- f2fs_lock_all down_write(cp_rwsem)
- f2fs_lock_op down_read(cp_rwsem)
So in this path, we pass parameter to f2fs_truncate to make sure
cp_rwsem in truncate_blocks will not be locked again.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch adds to stat the number of inline xattr inode for
showing in debugfs.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
We don't need to handle the duplicate extent information.
The integrated rule is:
- update on-disk extent with largest one tracked by in-memory extent_cache
- destroy extent_tree for the truncation case
- drop per-inode extent_cache by shrinker
Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Before iput is called, the inode number used by a bad inode can be reassigned
to other new inode, resulting in any abnormal behaviors on the new inode.
This should not happen for the new inode.
Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch applies the following ext4 patch:
ext4 crypto: use per-inode tfm structure
As suggested by Herbert Xu, we shouldn't allocate a new tfm each time
we read or write a page. Instead we can use a single tfm hanging off
the inode's crypt_info structure for all of our encryption needs for
that inode, since the tfm can be used by multiple crypto requests in
parallel.
Also use cmpxchg() to avoid races that could result in crypt_info
structure getting doubly allocated or doubly freed.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch implements encryption support for symlink.
Signed-off-by: Uday Savagaonkar <savagaon@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch activates the following APIs for encryption support.
The rules quoted by ext4 are:
- An unencrypted directory may contain encrypted or unencrypted files
or directories.
- All files or directories in a directory must be protected using the
same key as their containing directory.
- Encrypted inode for regular file should not have inline_data.
- Encrypted symlink and directory may have inline_data and inline_dentry.
This patch activates the following APIs.
1. f2fs_link : validate context
2. f2fs_lookup : ''
3. f2fs_rename : ''
4. f2fs_create/f2fs_mkdir : inherit its dir's context
5. f2fs_direct_IO : do buffered io for regular files
6. f2fs_open : check encryption info
7. f2fs_file_mmap : ''
8. f2fs_setattr : ''
9. f2fs_file_write_iter : '' (Called by sys_io_submit)
10. f2fs_fallocate : do not support fcollapse
11. f2fs_evict_inode : free_encryption_info
Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch fixes the below warning.
sparse warnings: (new ones prefixed by >>)
>> fs/f2fs/inode.c:56:23: sparse: restricted __le32 degrades to integer
>> fs/f2fs/inode.c:56:52: sparse: restricted __le32 degrades to integer
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch tries to preserve last extent info in extent tree cache into on-disk
inode, so this can help us to reuse the last extent info next time for
performance.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
With normal extent info cache, we records largest extent mapping between logical
block and physical block into extent info, and we persist extent info in on-disk
inode.
When we enable extent tree cache, if extent info of on-disk inode is exist, and
the extent is not a small fragmented mapping extent. We'd better to load the
extent info into extent tree cache when inode is loaded. By this way we can have
more chance to hit extent tree cache rather than taking more time to read dnode
page for block address.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch is to avoid some punch_hole overhead when releasing volatile data.
If volatile data was not written yet, we just can make the first page as zero.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch enables rb-tree based extent cache in f2fs.
When we mount with "-o extent_cache", f2fs will try to add recently accessed
page-block mappings into rb-tree based extent cache as much as possible, instead
of original one extent info cache.
By this way, f2fs can support more effective cache between dnode page cache and
disk. It will supply high hit ratio in the cache with fewer memory when dnode
page cache are reclaimed in environment of low memory.
Storage: Sandisk sd card 64g
1.append write file (offset: 0, size: 128M);
2.override write file (offset: 2M, size: 1M);
3.override write file (offset: 4M, size: 1M);
...
4.override write file (offset: 48M, size: 1M);
...
5.override write file (offset: 112M, size: 1M);
6.sync
7.echo 3 > /proc/sys/vm/drop_caches
8.read file (size:128M, unit: 4k, count: 32768)
(time dd if=/mnt/f2fs/128m bs=4k count=32768)
Extent Hit Ratio:
before patched
Hit Ratio 121 / 1071 1071 / 1071
Performance:
before patched
real 0m37.051s 0m35.556s
user 0m0.040s 0m0.026s
sys 0m2.990s 0m2.251s
Memory Cost:
before patched
Tree Count: 0 1 (size: 24 bytes)
Node Count: 0 45 (size: 1440 bytes)
v3:
o retest and given more details of test result.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Move ext_lock out of struct extent_info, then in the following patches we can
use variables with struct extent_info type as a parameter to pass pure data.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
We use kzalloc to allocate memory in __recover_inline_status, and use this
all-zero memory to check the inline date content of inode page by comparing
them. This is low effective and not needed, let's check inline date content
directly.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
[Jaegeuk Kim: make the code more neat]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch adds two new ioctls to release inmemory pages grabbed by atomic
writes.
o f2fs_ioc_abort_volatile_write
- If transaction was failed, all the grabbed pages and data should be written.
o f2fs_ioc_release_volatile_write
- This is to enhance the performance of PERSIST mode in sqlite.
In order to avoid huge memory consumption which causes OOM, this patch changes
volatile writes to use normal dirty pages, instead blocked flushing to the disk
as long as system does not suffer from memory pressure.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
In do_read_inode, if we failed __recover_inline_status, the inode has inline
flag without increasing its count.
Later, f2fs_evict_inode will decrease the count, which causes -1.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch simplifies the inline_data usage with the following rule.
1. inline_data is set during the file creation.
2. If new data is requested to be written ranges out of inline_data,
f2fs converts that inode permanently.
3. There is no cases which converts non-inline_data inode to inline_data.
4. The inline_data flag should be changed under inode page lock.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch adds support for volatile writes which keep data pages in memory
until f2fs_evict_inode is called by iput.
For instance, we can use this feature for the sqlite database as follows.
While supporting atomic writes for main database file, we can keep its journal
data temporarily in the page cache by the following sequence.
1. open
-> ioctl(F2FS_IOC_START_VOLATILE_WRITE);
2. writes
: keep all the data in the page cache.
3. flush to the database file with atomic writes
a. ioctl(F2FS_IOC_START_ATOMIC_WRITE);
b. writes
c. ioctl(F2FS_IOC_COMMIT_ATOMIC_WRITE);
4. close
-> drop the cached data
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch introduces a very limited functionality for atomic write support.
In order to support atomic write, this patch adds two ioctls:
o F2FS_IOC_START_ATOMIC_WRITE
o F2FS_IOC_COMMIT_ATOMIC_WRITE
The database engine should be aware of the following sequence.
1. open
-> ioctl(F2FS_IOC_START_ATOMIC_WRITE);
2. writes
: all the written data will be treated as atomic pages.
3. commit
-> ioctl(F2FS_IOC_COMMIT_ATOMIC_WRITE);
: this flushes all the data blocks to the disk, which will be shown all or
nothing by f2fs recovery procedure.
4. repeat to #2.
The IO pattens should be:
,- START_ATOMIC_WRITE ,- COMMIT_ATOMIC_WRITE
CP | D D D D D D | FSYNC | D D D D | FSYNC ...
`- COMMIT_ATOMIC_WRITE
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch relocates f2fs_unlock_op in every directory operations to be called
after any error was processed.
Otherwise, the checkpoint can be entered with valid node ids without its
dentry when -ENOSPC is occurred.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Previously f2fs only counts dirty dentry pages, but there is no reason not to
expand the scope.
This patch changes the names on the management of dirty pages and to count
dirty pages in each inode info as well.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
When inode is evicted, all the page cache belong to this inode should be
released including the xattr node page. But previously we didn't do this, this
patch fixed this issue.
v2:
o reposition invalidate_mapping_pages() to the right place suggested by
Jaegeuk Kim.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch introduces a inode number list in which represents inodes having
appended data writes or updated data writes after last checkpoint.
This will be used at fsync to determine whether the recovery information
should be written or not.
Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch add lower bound verification for nid in check_nid_range, so nids
reserved like 0, node, meta passed by caller could be checked there.
And then check_nid_range could be used in f2fs_nfs_get_inode for simplifying
code.
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
If the inode page is clean during its inode eviction, it'd better drop the page
to reduce further memory pressure.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Use set_mask_bits() to atomically set i_flags instead of clearing out the
S_IMMUTABLE, S_APPEND, etc. flags and then setting them from the
FS_IMMUTABLE_FL, FS_APPEND_FL, etc. flags, since this opens up a race
where an immutable file has the immutable flag cleared for a brief
window of time.
Signed-off-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
This patch-set includes the following major enhancement patches.
o introduce large directory support
o introduce f2fs_issue_flush to merge redundant flush commands
o merge write IOs as much as possible aligned to the segment
o add sysfs entries to tune the f2fs configuration
o use radix_tree for the free_nid_list to reduce in-memory operations
o remove costly bit operations in f2fs_find_entry
o enhance the readahead flow for CP/NAT/SIT/SSA blocks
The other bug fixes are as follows.
o recover xattr node blocks correctly after sudden-power-cut
o fix to calculate the maximum number of node ids
o enhance to handle many error cases
And, there are a bunch of cleanups.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (GNU/Linux)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=eSW+
-----END PGP SIGNATURE-----
Merge tag 'for-f2fs-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs
Pull f2fs updates from Jaegeuk Kim:
"This patch-set includes the following major enhancement patches.
- introduce large directory support
- introduce f2fs_issue_flush to merge redundant flush commands
- merge write IOs as much as possible aligned to the segment
- add sysfs entries to tune the f2fs configuration
- use radix_tree for the free_nid_list to reduce in-memory operations
- remove costly bit operations in f2fs_find_entry
- enhance the readahead flow for CP/NAT/SIT/SSA blocks
The other bug fixes are as follows:
- recover xattr node blocks correctly after sudden-power-cut
- fix to calculate the maximum number of node ids
- enhance to handle many error cases
And, there are a bunch of cleanups"
* tag 'for-f2fs-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (62 commits)
f2fs: fix wrong statistics of inline data
f2fs: check the acl's validity before setting
f2fs: introduce f2fs_issue_flush to avoid redundant flush issue
f2fs: fix to cover io->bio with io_rwsem
f2fs: fix error path when fail to read inline data
f2fs: use list_for_each_entry{_safe} for simplyfying code
f2fs: avoid free slab cache under spinlock
f2fs: avoid unneeded lookup when xattr name length is too long
f2fs: avoid unnecessary bio submit when wait page writeback
f2fs: return -EIO when node id is not matched
f2fs: avoid RECLAIM_FS-ON-W warning
f2fs: skip unnecessary node writes during fsync
f2fs: introduce fi->i_sem to protect fi's info
f2fs: change reclaim rate in percentage
f2fs: add missing documentation for dir_level
f2fs: remove unnecessary threshold
f2fs: throttle the memory footprint with a sysfs entry
f2fs: avoid to drop nat entries due to the negative nr_shrink
f2fs: call f2fs_wait_on_page_writeback instead of native function
f2fs: introduce nr_pages_to_write for segment alignment
...
Reclaim will be leaving shadow entries in the page cache radix tree upon
evicting the real page. As those pages are found from the LRU, an
iput() can lead to the inode being freed concurrently. At this point,
reclaim must no longer install shadow pages because the inode freeing
code needs to ensure the page tree is really empty.
Add an address_space flag, AS_EXITING, that the inode freeing code sets
under the tree lock before doing the final truncate. Reclaim will check
for this flag before installing shadow pages.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Metin Doslu <metin@citusdata.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Ozgun Erdogan <ozgun@citusdata.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch introduces an i_dir_level field to support large directory.
Previously, f2fs maintains multi-level hash tables to find a dentry quickly
from a bunch of chiild dentries in a directory, and the hash tables consist of
the following tree structure as below.
In Documentation/filesystems/f2fs.txt,
----------------------
A : bucket
B : block
N : MAX_DIR_HASH_DEPTH
----------------------
level #0 | A(2B)
|
level #1 | A(2B) - A(2B)
|
level #2 | A(2B) - A(2B) - A(2B) - A(2B)
. | . . . .
level #N/2 | A(2B) - A(2B) - A(2B) - A(2B) - A(2B) - ... - A(2B)
. | . . . .
level #N | A(4B) - A(4B) - A(4B) - A(4B) - A(4B) - ... - A(4B)
But, if we can guess that a directory will handle a number of child files,
we don't need to traverse the tree from level #0 to #N all the time.
Since the lower level tables contain relatively small number of dentries,
the miss ratio of the target dentry is likely to be high.
In order to avoid that, we can configure the hash tables sparsely from level #0
like this.
level #0 | A(2B) - A(2B) - A(2B) - A(2B)
level #1 | A(2B) - A(2B) - A(2B) - A(2B) - A(2B) - ... - A(2B)
. | . . . .
level #N/2 | A(2B) - A(2B) - A(2B) - A(2B) - A(2B) - ... - A(2B)
. | . . . .
level #N | A(4B) - A(4B) - A(4B) - A(4B) - A(4B) - ... - A(4B)
With this structure, we can skip the ineffective tree searches in lower level
hash tables.
This patch adds just a facility for this by introducing i_dir_level in
f2fs_inode.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Chao Yu