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authorJan Kara <jack@suse.cz>2017-04-05 14:17:30 +0200
committerJan Kara <jack@suse.cz>2017-04-05 14:24:55 +0200
commit1e0e653f1136a413a9969e5d0d548ee6499b9763 (patch)
treea3e413e0affd13b0906dafa495501ee70216106d /fs/reiserfs
parent71b0576bdb862e964a82c73327cdd1a249c53e67 (diff)
downloadlinux-1e0e653f1136a413a9969e5d0d548ee6499b9763.tar.bz2
reiserfs: Protect dquot_writeback_dquots() by s_umount semaphore
dquot_writeback_dquots() expects s_umount semaphore to be held to protect it from other concurrent quota operations. reiserfs_sync_fs() can call dquot_writeback_dquots() without holding s_umount semaphore when called from flush_old_commits(). Fix the problem by grabbing s_umount in flush_old_commits(). However we have to be careful and use only trylock since reiserfs_cancel_old_sync() can be waiting for flush_old_commits() to complete while holding s_umount semaphore. Possible postponing of sync work is not a big deal though as that is only an opportunistic flush. Fixes: 9d1ccbe70e0b14545caad12dc73adb3605447df0 Reported-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/reiserfs')
-rw-r--r--fs/reiserfs/super.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/fs/reiserfs/super.c b/fs/reiserfs/super.c
index 91cf5cbd6332..f536e12c4b1d 100644
--- a/fs/reiserfs/super.c
+++ b/fs/reiserfs/super.c
@@ -89,6 +89,19 @@ static void flush_old_commits(struct work_struct *work)
sbi = container_of(work, struct reiserfs_sb_info, old_work.work);
s = sbi->s_journal->j_work_sb;
+ /*
+ * We need s_umount for protecting quota writeback. We have to use
+ * trylock as reiserfs_cancel_old_flush() may be waiting for this work
+ * to complete with s_umount held.
+ */
+ if (!down_read_trylock(&s->s_umount)) {
+ /* Requeue work if we are not cancelling it */
+ spin_lock(&sbi->old_work_lock);
+ if (sbi->work_queued == 1)
+ queue_delayed_work(system_long_wq, &sbi->old_work, HZ);
+ spin_unlock(&sbi->old_work_lock);
+ return;
+ }
spin_lock(&sbi->old_work_lock);
/* Avoid clobbering the cancel state... */
if (sbi->work_queued == 1)
@@ -96,6 +109,7 @@ static void flush_old_commits(struct work_struct *work)
spin_unlock(&sbi->old_work_lock);
reiserfs_sync_fs(s, 1);
+ up_read(&s->s_umount);
}
void reiserfs_schedule_old_flush(struct super_block *s)