From c8585c6fcaf2011de54c3592e80a634a2b9e1a7f Mon Sep 17 00:00:00 2001 From: Daeho Jeong Date: Mon, 25 Apr 2016 23:22:35 -0400 Subject: 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 Signed-off-by: Theodore Ts'o Reviewed-by: Jan Kara --- kernel/locking/percpu-rwsem.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/locking') 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 -- cgit v1.2.3-59-g8ed1b