f2fs: do sanity check on inode footer in f2fs_get_inode_page()

This patch introduces a new wrapper f2fs_get_inode_page(), then, caller
can use it to load inode block to page cache, meanwhile it will

f2fs: do sanity check on inode footer in f2fs_get_inode_page()

This patch introduces a new wrapper f2fs_get_inode_page(), then, caller
can use it to load inode block to page cache, meanwhile it will do sanity
check on inode footer.

Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: Introduce linear search for dentries

This patch addresses an issue where some files in case-insensitive
directories become inaccessible due to changes in how the kernel function,
utf8_casefold

f2fs: Introduce linear search for dentries

This patch addresses an issue where some files in case-insensitive
directories become inaccessible due to changes in how the kernel function,
utf8_casefold(), generates case-folded strings from the commit 5c26d2f1d3f5
("unicode: Don't special case ignorable code points").

F2FS uses these case-folded names to calculate hash values for locating
dentries and stores them on disk. Since utf8_casefold() can produce
different output across kernel versions, stored hash values and newly
calculated hash values may differ. This results in affected files no
longer being found via the hash-based lookup.

To resolve this, the patch introduces a linear search fallback.
If the initial hash-based search fails, F2FS will sequentially scan the
directory entries.

Fixes: 5c26d2f1d3f5 ("unicode: Don't special case ignorable code points")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219586
Signed-off-by: Daniel Lee <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: Remove calls to folio_file_mapping()

All folios that f2fs sees belong to f2fs and not to the swapcache
so it can dereference folio->mapping directly like all other
filesystems do.

Signed-off-

f2fs: Remove calls to folio_file_mapping()

All folios that f2fs sees belong to f2fs and not to the swapcache
so it can dereference folio->mapping directly like all other
filesystems do.

Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: convert f2fs_write_inline_data() to use folio

Convert to use folio, so that we can get rid of 'page->index' to
prepare for removal of 'index' field in structure page [1].

[1] https://lore.ker

f2fs: convert f2fs_write_inline_data() to use folio

Convert to use folio, so that we can get rid of 'page->index' to
prepare for removal of 'index' field in structure page [1].

[1] https://lore.kernel.org/all/[email protected]/

Cc: Matthew Wilcox <[email protected]>
Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: convert f2fs_clear_page_cache_dirty_tag() to use folio

Convert to use folio, so that we can get rid of 'page->index' to
prepare for removal of 'index' field in structure page [1].

[1] https:/

f2fs: convert f2fs_clear_page_cache_dirty_tag() to use folio

Convert to use folio, so that we can get rid of 'page->index' to
prepare for removal of 'index' field in structure page [1].

[1] https://lore.kernel.org/all/[email protected]/

Cc: Matthew Wilcox <[email protected]>
Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: use f2fs_get_node_page when write inline data

We just need inode page when write inline data, use
f2fs_get_node_page() to get it instead of using dnode_of_data,
which can eliminate unnecessary

f2fs: use f2fs_get_node_page when write inline data

We just need inode page when write inline data, use
f2fs_get_node_page() to get it instead of using dnode_of_data,
which can eliminate unnecessary struct use.

Signed-off-by: Zijie Wang <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: use meta inode for GC of COW file

In case of the COW file, new updates and GC writes are already
separated to page caches of the atomic file and COW file. As some cases
that use the meta inode

f2fs: use meta inode for GC of COW file

In case of the COW file, new updates and GC writes are already
separated to page caches of the atomic file and COW file. As some cases
that use the meta inode for GC, there are some race issues between a
foreground thread and GC thread.

To handle them, we need to take care when to invalidate and wait
writeback of GC pages in COW files as the case of using the meta inode.
Also, a pointer from the COW inode to the original inode is required to
check the state of original pages.

For the former, we can solve the problem by using the meta inode for GC
of COW files. Then let's get a page from the original inode in
move_data_block when GCing the COW file to avoid race condition.

Fixes: 3db1de0e582c ("f2fs: change the current atomic write way")
Cc: [email protected] #v5.19+
Reviewed-by: Sungjong Seo <[email protected]>
Reviewed-by: Yeongjin Gil <[email protected]>
Signed-off-by: Sunmin Jeong <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: fix return value of f2fs_convert_inline_inode()

If device is readonly, make f2fs_convert_inline_inode()
return EROFS instead of zero, otherwise it may trigger
panic during writeback of inline

f2fs: fix return value of f2fs_convert_inline_inode()

If device is readonly, make f2fs_convert_inline_inode()
return EROFS instead of zero, otherwise it may trigger
panic during writeback of inline inode's dirty page as
below:

f2fs_write_single_data_page+0xbb6/0x1e90 fs/f2fs/data.c:2888
f2fs_write_cache_pages fs/f2fs/data.c:3187 [inline]
__f2fs_write_data_pages fs/f2fs/data.c:3342 [inline]
f2fs_write_data_pages+0x1efe/0x3a90 fs/f2fs/data.c:3369
do_writepages+0x359/0x870 mm/page-writeback.c:2634
filemap_fdatawrite_wbc+0x125/0x180 mm/filemap.c:397
__filemap_fdatawrite_range mm/filemap.c:430 [inline]
file_write_and_wait_range+0x1aa/0x290 mm/filemap.c:788
f2fs_do_sync_file+0x68a/0x1ae0 fs/f2fs/file.c:276
generic_write_sync include/linux/fs.h:2806 [inline]
f2fs_file_write_iter+0x7bd/0x24e0 fs/f2fs/file.c:4977
call_write_iter include/linux/fs.h:2114 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0xa72/0xc90 fs/read_write.c:590
ksys_write+0x1a0/0x2c0 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Cc: [email protected]
Reported-by: [email protected]
Closes: https://lore.kernel.org/linux-f2fs-devel/[email protected]
Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: fix to do sanity check on blocks for inline_data inode

inode can be fuzzed, so it can has F2FS_INLINE_DATA flag and valid
i_blocks/i_nid value, this patch supports to do extra sanity check
to

f2fs: fix to do sanity check on blocks for inline_data inode

inode can be fuzzed, so it can has F2FS_INLINE_DATA flag and valid
i_blocks/i_nid value, this patch supports to do extra sanity check
to detect such corrupted state.

Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: convert f2fs_read_inline_data() to use folio

Convert f2fs_read_inline_data() to use folio and related
functionality, and also convert its caller to use folio.

Signed-off-by: Chao Yu <chao@ker

f2fs: convert f2fs_read_inline_data() to use folio

Convert f2fs_read_inline_data() to use folio and related
functionality, and also convert its caller to use folio.

Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: use folio_test_writeback

Let's convert PageWriteback to folio_test_writeback.

Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

f2fs: convert to new timestamp accessors

Convert to using the new inode timestamp accessor functions.

Signed-off-by: Jeff Layton <[email protected]>
Link: https://lore.kernel.org/r/20231004185347.

f2fs: convert to new timestamp accessors

Convert to using the new inode timestamp accessor functions.

Signed-off-by: Jeff Layton <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Christian Brauner <[email protected]>

show more ...

f2fs: avoid false alarm of circular locking

======================================================
WARNING: possible circular locking dependency detected
6.5.0-rc5-syzkaller-00353-gae545c3283dc #0 N

f2fs: avoid false alarm of circular locking

======================================================
WARNING: possible circular locking dependency detected
6.5.0-rc5-syzkaller-00353-gae545c3283dc #0 Not tainted
------------------------------------------------------
syz-executor273/5027 is trying to acquire lock:
ffff888077fe1fb0 (&fi->i_sem){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2133 [inline]
ffff888077fe1fb0 (&fi->i_sem){+.+.}-{3:3}, at: f2fs_add_inline_entry+0x300/0x6f0 fs/f2fs/inline.c:644

but task is already holding lock:
ffff888077fe07c8 (&fi->i_xattr_sem){.+.+}-{3:3}, at: f2fs_down_read fs/f2fs/f2fs.h:2108 [inline]
ffff888077fe07c8 (&fi->i_xattr_sem){.+.+}-{3:3}, at: f2fs_add_dentry+0x92/0x230 fs/f2fs/dir.c:783

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&fi->i_xattr_sem){.+.+}-{3:3}:
down_read+0x9c/0x470 kernel/locking/rwsem.c:1520
f2fs_down_read fs/f2fs/f2fs.h:2108 [inline]
f2fs_getxattr+0xb1e/0x12c0 fs/f2fs/xattr.c:532
__f2fs_get_acl+0x5a/0x900 fs/f2fs/acl.c:179
f2fs_acl_create fs/f2fs/acl.c:377 [inline]
f2fs_init_acl+0x15c/0xb30 fs/f2fs/acl.c:420
f2fs_init_inode_metadata+0x159/0x1290 fs/f2fs/dir.c:558
f2fs_add_regular_entry+0x79e/0xb90 fs/f2fs/dir.c:740
f2fs_add_dentry+0x1de/0x230 fs/f2fs/dir.c:788
f2fs_do_add_link+0x190/0x280 fs/f2fs/dir.c:827
f2fs_add_link fs/f2fs/f2fs.h:3554 [inline]
f2fs_mkdir+0x377/0x620 fs/f2fs/namei.c:781
vfs_mkdir+0x532/0x7e0 fs/namei.c:4117
do_mkdirat+0x2a9/0x330 fs/namei.c:4140
__do_sys_mkdir fs/namei.c:4160 [inline]
__se_sys_mkdir fs/namei.c:4158 [inline]
__x64_sys_mkdir+0xf2/0x140 fs/namei.c:4158
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&fi->i_sem){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3142 [inline]
check_prevs_add kernel/locking/lockdep.c:3261 [inline]
validate_chain kernel/locking/lockdep.c:3876 [inline]
__lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5144
lock_acquire kernel/locking/lockdep.c:5761 [inline]
lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5726
down_write+0x93/0x200 kernel/locking/rwsem.c:1573
f2fs_down_write fs/f2fs/f2fs.h:2133 [inline]
f2fs_add_inline_entry+0x300/0x6f0 fs/f2fs/inline.c:644
f2fs_add_dentry+0xa6/0x230 fs/f2fs/dir.c:784
f2fs_do_add_link+0x190/0x280 fs/f2fs/dir.c:827
f2fs_add_link fs/f2fs/f2fs.h:3554 [inline]
f2fs_mkdir+0x377/0x620 fs/f2fs/namei.c:781
vfs_mkdir+0x532/0x7e0 fs/namei.c:4117
ovl_do_mkdir fs/overlayfs/overlayfs.h:196 [inline]
ovl_mkdir_real+0xb5/0x370 fs/overlayfs/dir.c:146
ovl_workdir_create+0x3de/0x820 fs/overlayfs/super.c:309
ovl_make_workdir fs/overlayfs/super.c:711 [inline]
ovl_get_workdir fs/overlayfs/super.c:864 [inline]
ovl_fill_super+0xdab/0x6180 fs/overlayfs/super.c:1400
vfs_get_super+0xf9/0x290 fs/super.c:1152
vfs_get_tree+0x88/0x350 fs/super.c:1519
do_new_mount fs/namespace.c:3335 [inline]
path_mount+0x1492/0x1ed0 fs/namespace.c:3662
do_mount fs/namespace.c:3675 [inline]
__do_sys_mount fs/namespace.c:3884 [inline]
__se_sys_mount fs/namespace.c:3861 [inline]
__x64_sys_mount+0x293/0x310 fs/namespace.c:3861
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
rlock(&fi->i_xattr_sem);
lock(&fi->i_sem);
lock(&fi->i_xattr_sem);
lock(&fi->i_sem);

Cc: <[email protected]>
Reported-and-tested-by: [email protected]
Fixes: 5eda1ad1aaff "f2fs: fix deadlock in i_xattr_sem and inode page lock"
Tested-by: Guenter Roeck <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: convert to ctime accessor functions

In later patches, we're going to change how the inode's ctime field is
used. Switch to using accessor functions instead of raw accesses of
inode->i_ctime.

f2fs: convert to ctime accessor functions

In later patches, we're going to change how the inode's ctime field is
used. Switch to using accessor functions instead of raw accesses of
inode->i_ctime.

Signed-off-by: Jeff Layton <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

show more ...

f2fs: use common implementation of file type

Use common implementation of file type conversion helpers.

Signed-off-by: Weizhao Ouyang <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
S

f2fs: use common implementation of file type

Use common implementation of file type conversion helpers.

Signed-off-by: Weizhao Ouyang <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: fix information leak in f2fs_move_inline_dirents()

When converting an inline directory to a regular one, f2fs is leaking
uninitialized memory to disk because it doesn't initialize the entire
d

f2fs: fix information leak in f2fs_move_inline_dirents()

When converting an inline directory to a regular one, f2fs is leaking
uninitialized memory to disk because it doesn't initialize the entire
directory block. Fix this by zero-initializing the block.

This bug was introduced by commit 4ec17d688d74 ("f2fs: avoid unneeded
initializing when converting inline dentry"), which didn't consider the
security implications of leaking uninitialized memory to disk.

This was found by running xfstest generic/435 on a KMSAN-enabled kernel.

Fixes: 4ec17d688d74 ("f2fs: avoid unneeded initializing when converting inline dentry")
Cc: <[email protected]> # v4.3+
Signed-off-by: Eric Biggers <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: avoid to check PG_error flag

After below changes:
commit 14db0b3c7b83 ("fscrypt: stop using PG_error to track error status")
commit 98dc08bae678 ("fsverity: stop using PG_error to track error

f2fs: avoid to check PG_error flag

After below changes:
commit 14db0b3c7b83 ("fscrypt: stop using PG_error to track error status")
commit 98dc08bae678 ("fsverity: stop using PG_error to track error status")

There is no place in f2fs we will set PG_error flag in page, let's remove
other PG_error usage in f2fs, as a step towards freeing the PG_error flag
for other uses.

Cc: Eric Biggers <[email protected]>
Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: support recording errors into superblock

This patch supports to record detail reason of FSCORRUPTED error into
f2fs_super_block.s_errors[].

Signed-off-by: Chao Yu <[email protected]>
Signed-off

f2fs: support recording errors into superblock

This patch supports to record detail reason of FSCORRUPTED error into
f2fs_super_block.s_errors[].

Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: use memcpy_{to,from}_page() where possible

This is simpler, and as a side effect it replaces several uses of
kmap_atomic() with its recommended replacement kmap_local_page().

Signed-off-by: E

f2fs: use memcpy_{to,from}_page() where possible

This is simpler, and as a side effect it replaces several uses of
kmap_atomic() with its recommended replacement kmap_local_page().

Signed-off-by: Eric Biggers <[email protected]>
Reviewed-by: Fabio M. De Francesco <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: fix to do sanity check for inline inode

Yanming reported a kernel bug in Bugzilla kernel [1], which can be
reproduced. The bug message is:

The kernel message is shown below:

kernel BUG at fs

f2fs: fix to do sanity check for inline inode

Yanming reported a kernel bug in Bugzilla kernel [1], which can be
reproduced. The bug message is:

The kernel message is shown below:

kernel BUG at fs/inode.c:611!
Call Trace:
evict+0x282/0x4e0
__dentry_kill+0x2b2/0x4d0
dput+0x2dd/0x720
do_renameat2+0x596/0x970
__x64_sys_rename+0x78/0x90
do_syscall_64+0x3b/0x90

[1] https://bugzilla.kernel.org/show_bug.cgi?id=215895

The bug is due to fuzzed inode has both inline_data and encrypted flags.
During f2fs_evict_inode(), as the inode was deleted by rename(), it
will cause inline data conversion due to conflicting flags. The page
cache will be polluted and the panic will be triggered in clear_inode().

Try fixing the bug by doing more sanity checks for inline data inode in
sanity_check_inode().

Cc: [email protected]
Reported-by: Ming Yan <[email protected]>
Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reade

f2fs: move f2fs to use reader-unfair rwsems

f2fs rw_semaphores work better if writers can starve readers,
especially for the checkpoint thread, because writers are strictly
more important than reader threads. This prevents significant priority
inversion between low-priority readers that blocked while trying to
acquire the read lock and a second acquisition of the write lock that
might be blocking high priority work.

Signed-off-by: Tim Murray <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: do not bother checkpoint by f2fs_get_node_info

This patch tries to mitigate lock contention between f2fs_write_checkpoint and
f2fs_get_node_info along with nat_tree_lock.

The idea is, if chec

f2fs: do not bother checkpoint by f2fs_get_node_info

This patch tries to mitigate lock contention between f2fs_write_checkpoint and
f2fs_get_node_info along with nat_tree_lock.

The idea is, if checkpoint is currently running, other threads that try to grab
nat_tree_lock would be better to wait for checkpoint.

Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: support fault injection for dquot_initialize()

This patch adds a new function f2fs_dquot_initialize() to wrap
dquot_initialize(), and it supports to inject fault into
f2fs_dquot_initialize() t

f2fs: support fault injection for dquot_initialize()

This patch adds a new function f2fs_dquot_initialize() to wrap
dquot_initialize(), and it supports to inject fault into
f2fs_dquot_initialize() to simulate inner failure occurs in
dquot_initialize().

Usage:
a) echo 65536 > /sys/fs/f2fs/<dev>/inject_type or
b) mount -o fault_type=65536 <dev> <mountpoint>

Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: restructure f2fs page.private layout

Restruct f2fs page private layout for below reasons:

There are some cases that f2fs wants to set a flag in a page to
indicate a specified status of page:

f2fs: restructure f2fs page.private layout

Restruct f2fs page private layout for below reasons:

There are some cases that f2fs wants to set a flag in a page to
indicate a specified status of page:
a) page is in transaction list for atomic write
b) page contains dummy data for aligned write
c) page is migrating for GC
d) page contains inline data for inline inode flush
e) page belongs to merkle tree, and is verified for fsverity
f) page is dirty and has filesystem/inode reference count for writeback
g) page is temporary and has decompress io context reference for compression

There are existed places in page structure we can use to store
f2fs private status/data:
- page.flags: PG_checked, PG_private
- page.private

However it was a mess when we using them, which may cause potential
confliction:
page.private PG_private PG_checked page._refcount (+1 at most)
a) -1 set +1
b) -2 set
c), d), e) set
f) 0 set +1
g) pointer set

The other problem is page.flags has no free slot, if we can avoid set
zero to page.private and set PG_private flag, then we use non-zero value
to indicate PG_private status, so that we may have chance to reclaim
PG_private slot for other usage. [1]

The other concern is f2fs has bad scalability in aspect of indicating
more page status.

So in this patch, let's restructure f2fs' page.private as below to
solve above issues:

Layout A: lowest bit should be 1
| bit0 = 1 | bit1 | bit2 | ... | bit MAX | private data .... |
bit 0 PAGE_PRIVATE_NOT_POINTER
bit 1 PAGE_PRIVATE_ATOMIC_WRITE
bit 2 PAGE_PRIVATE_DUMMY_WRITE
bit 3 PAGE_PRIVATE_ONGOING_MIGRATION
bit 4 PAGE_PRIVATE_INLINE_INODE
bit 5 PAGE_PRIVATE_REF_RESOURCE
bit 6- f2fs private data

Layout B: lowest bit should be 0
page.private is a wrapped pointer.

After the change:
page.private PG_private PG_checked page._refcount (+1 at most)
a) 11 set +1
b) 101 set +1
c) 1001 set +1
d) 10001 set +1
e) set
f) 100001 set +1
g) pointer set +1

[1] https://lore.kernel.org/linux-f2fs-devel/[email protected]/T/#u

Cc: Matthew Wilcox <[email protected]>
Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

show more ...

f2fs: fix a redundant call to f2fs_balance_fs if an error occurs

The uninitialized variable dn.node_changed does not get set when a
call to f2fs_get_node_page fails. This uninitialized value gets

f2fs: fix a redundant call to f2fs_balance_fs if an error occurs

The uninitialized variable dn.node_changed does not get set when a
call to f2fs_get_node_page fails. This uninitialized value gets used
in the call to f2fs_balance_fs() that may or not may not balances
dirty node and dentry pages depending on the uninitialized state of
the variable. Fix this by only calling f2fs_balance_fs if err is
not set.

Thanks to Jaegeuk Kim for suggesting an appropriate fix.

Addresses-Coverity: ("Uninitialized scalar variable")
Fixes: 2a3407607028 ("f2fs: call f2fs_balance_fs only when node was changed")
Signed-off-by: Colin Ian King <[email protected]>
Reviewed-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>

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