Commit 7925409e authored by Jan Kara's avatar Jan Kara Committed by Linus Torvalds
Browse files

circular locking dependency found in QUOTA OFF 



i_mutex on quota files is special.  Unlike i_mutexes for other inodes it is
acquired under dqonoff_mutex.  Tell lockdep about this lock ranking.  Also
comment and code in quota_sync_sb() seem to be bogus (as i_mutex for quota
file can be acquired under dqonoff_mutex).  Move truncate_inode_pages()
call under dqonoff_mutex and save some problems with races...

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bb49b32f

fs/dquot.c

+1 −1
Original line number Diff line number Diff line
@@ -1421,7 +1421,7 @@ int vfs_quota_off(struct super_block *sb, int type) 
			/* If quota was reenabled in the meantime, we have

			 * nothing to do */

			if (!sb_has_quota_enabled(sb, cnt)) {

				mutex_lock(&toputinode[cnt]->i_mutex);

				mutex_lock_nested(&toputinode[cnt]->i_mutex, I_MUTEX_QUOTA);

				toputinode[cnt]->i_flags &= ~(S_IMMUTABLE |

				  S_NOATIME | S_NOQUOTA);

				truncate_inode_pages(&toputinode[cnt]->i_data, 0);

fs/quota.c

+7 −16
Original line number Diff line number Diff line
@@ -157,7 +157,6 @@ static int check_quotactl_valid(struct super_block *sb, int type, int cmd, qid_t 
static void quota_sync_sb(struct super_block *sb, int type)

{

	int cnt;

	struct inode *discard[MAXQUOTAS];



	sb->s_qcop->quota_sync(sb, type);

	/* This is not very clever (and fast) but currently I don't know about
@@ -167,29 +166,21 @@ static void quota_sync_sb(struct super_block *sb, int type) 
		sb->s_op->sync_fs(sb, 1);

	sync_blockdev(sb->s_bdev);



	/* Now when everything is written we can discard the pagecache so

	 * that userspace sees the changes. We need i_mutex and so we could

	 * not do it inside dqonoff_mutex. Moreover we need to be carefull

	 * about races with quotaoff() (that is the reason why we have own

	 * reference to inode). */

	/*

	 * Now when everything is written we can discard the pagecache so

	 * that userspace sees the changes.

	 */

	mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);

	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {

		discard[cnt] = NULL;

		if (type != -1 && cnt != type)

			continue;

		if (!sb_has_quota_enabled(sb, cnt))

			continue;

		discard[cnt] = igrab(sb_dqopt(sb)->files[cnt]);

		mutex_lock_nested(&sb_dqopt(sb)->files[cnt]->i_mutex, I_MUTEX_QUOTA);

		truncate_inode_pages(&sb_dqopt(sb)->files[cnt]->i_data, 0);

		mutex_unlock(&sb_dqopt(sb)->files[cnt]->i_mutex);

	}

	mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);

	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {

		if (discard[cnt]) {

			mutex_lock(&discard[cnt]->i_mutex);

			truncate_inode_pages(&discard[cnt]->i_data, 0);

			mutex_unlock(&discard[cnt]->i_mutex);

			iput(discard[cnt]);

		}

	}

}



void sync_dquots(struct super_block *sb, int type)

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