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Commit 1e0e653f authored by Jan Kara's avatar Jan Kara
Browse files

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: 9d1ccbe7
Reported-by: default avatarJan Beulich <jbeulich@suse.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 71b0576b

fs/reiserfs/super.c

+14 −0
Original line number Diff line number Diff line
@@ -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)