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| author | Jan Kara <jack@suse.cz> | 2017-04-05 14:17:30 +0200 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2017-04-05 14:24:55 +0200 |
| commit | 1e0e653f1136a413a9969e5d0d548ee6499b9763 (patch) | |
| tree | a3e413e0affd13b0906dafa495501ee70216106d | |
| parent | 71b0576bdb862e964a82c73327cdd1a249c53e67 (diff) | |
| download | lwn-1e0e653f1136a413a9969e5d0d548ee6499b9763.tar.gz lwn-1e0e653f1136a413a9969e5d0d548ee6499b9763.zip | |
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>
| -rw-r--r-- | fs/reiserfs/super.c | 14 |
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) |