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| author |   Daeho Jeong <daeho.jeong@samsung.com> | 2016-04-25 23:22:35 -0400 |
|---|---|---|
| committer |   Theodore Ts'o <tytso@mit.edu> | 2016-04-25 23:22:35 -0400 |
| commit | c8585c6fcaf2011de54c3592e80a634a2b9e1a7f (patch) | |
| tree | 66b440a3e710ab4b63ae20200735a594bffb74cd /kernel/locking/percpu-rwsem.c | |
| parent | ext4: handle unwritten or delalloc buffers before enabling data journaling (diff) | |
| download | linux-dev-c8585c6fcaf2011de54c3592e80a634a2b9e1a7f.tar.xz linux-dev-c8585c6fcaf2011de54c3592e80a634a2b9e1a7f.zip | |
ext4: fix races between changing inode journal mode and ext4_writepages
In ext4, there is a race condition between changing inode journal mode
and ext4_writepages(). While ext4_writepages() is executed on a
non-journalled mode inode, the inode's journal mode could be enabled
by ioctl() and then, some pages dirtied after switching the journal
mode will be still exposed to ext4_writepages() in non-journaled mode.
To resolve this problem, we use fs-wide per-cpu rw semaphore by Jan
Kara's suggestion because we don't want to waste ext4_inode_info's
space for this extra rare case.
Signed-off-by: Daeho Jeong <daeho.jeong@samsung.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'kernel/locking/percpu-rwsem.c')
| -rw-r--r-- | kernel/locking/percpu-rwsem.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index f231e0bb311c..bec0b647f9cc 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -37,6 +37,7 @@ void percpu_free_rwsem(struct percpu_rw_semaphore *brw) free_percpu(brw->fast_read_ctr); brw->fast_read_ctr = NULL; /* catch use after free bugs */ } +EXPORT_SYMBOL_GPL(percpu_free_rwsem); /* * This is the fast-path for down_read/up_read. If it succeeds we rely |