reiserfs: Protect dquot_writeback_dquots() by s_umount semaphore (1e0e653f) · Commits · 戴 / test

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: Reported-by:

Jan Beulich <jbeulich@suse.com> Signed-off-by:

Jan Kara <jack@suse.cz>

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)

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