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authorDaeho Jeong <daeho.jeong@samsung.com>2016-04-25 23:22:35 -0400
committerTheodore Ts'o <tytso@mit.edu>2016-04-25 23:22:35 -0400
commitc8585c6fcaf2011de54c3592e80a634a2b9e1a7f (patch)
tree66b440a3e710ab4b63ae20200735a594bffb74cd /kernel/locking/percpu-rwsem.c
parent4c54659269ecb799133758330e7ea2a6fa4c65ca (diff)
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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.c1
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