quota: fix infinite loop

If we fail to start a transaction when releasing dquot, we have to call
dquot_release() anyway to mark dquot structure as inactive.  Otherwise we
end in an infinite loop inside dqput().

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: xb <xavier.bru@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ext3/super.c

@@ -2578,8 +2578,11 @@ static int ext3_release_dquot(struct dquot *dquot)
 
 	handle = ext3_journal_start(dquot_to_inode(dquot),
 					EXT3_QUOTA_DEL_BLOCKS(dquot->dq_sb));
-	if (IS_ERR(handle))
+	if (IS_ERR(handle)) {
+		/* Release dquot anyway to avoid endless cycle in dqput() */
+		dquot_release(dquot);
 		return PTR_ERR(handle);
+	}
 	ret = dquot_release(dquot);
 	err = ext3_journal_stop(handle);
 	if (!ret)
@@ -2712,6 +2715,12 @@ static ssize_t ext3_quota_write(struct super_block *sb, int type,
 	struct buffer_head *bh;
 	handle_t *handle = journal_current_handle();
 
+	if (!handle) {
+		printk(KERN_WARNING "EXT3-fs: Quota write (off=%Lu, len=%Lu)"
+			" cancelled because transaction is not started.\n",
+			(unsigned long long)off, (unsigned long long)len);
+		return -EIO;
+	}
 	mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA);
 	while (towrite > 0) {
 		tocopy = sb->s_blocksize - offset < towrite ?