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: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/dquot.c b/fs/dquot.c
index 3a995841de90e0f648dc915ba450a2aaf7fa9674..8819d281500c977118c8e0af8bf0ee0904f966e4 100644 (file)
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -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);

diff --git a/fs/quota.c b/fs/quota.c
index e9d88fd0eca8f48917871653fd489bdb5d28b554..9f237d6182c90e10129f6810279da32259fab6fe 100644 (file)
--- a/fs/quota.c
+++ b/fs/quota.c
@@ -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)