From 1e0e653f1136a413a9969e5d0d548ee6499b9763 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Wed, 5 Apr 2017 14:17:30 +0200 Subject: 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 Signed-off-by: Jan Kara --- fs/reiserfs/super.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'fs') 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) -- cgit v1.2.3