[PATCH] return ENOENT from ext3_link when racing with unlink

Return -ENOENT from ext[34]_link if we've raced with unlink and i_nlink is
0.  Doing otherwise has the potential to corrupt the orphan inode list,
because we'd wind up with an inode with a non-zero link count on the list,
and it will never get properly cleaned up & removed from the orphan list
before it is freed.

[akpm@osdl.org: build fix]
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ext3/namei.c

@@ -2191,6 +2191,12 @@ static int ext3_link (struct dentry * old_dentry,
 
 	if (inode->i_nlink >= EXT3_LINK_MAX)
 		return -EMLINK;
+	/*
+	 * Return -ENOENT if we've raced with unlink and i_nlink is 0.  Doing
+	 * otherwise has the potential to corrupt the orphan inode list.
+	 */
+	if (inode->i_nlink == 0)
+		return -ENOENT;
 
 retry:
 	handle = ext3_journal_start(dir, EXT3_DATA_TRANS_BLOCKS(dir->i_sb) +

fs/ext4/namei.c

@@ -2189,6 +2189,12 @@ static int ext4_link (struct dentry * old_dentry,
 
 	if (inode->i_nlink >= EXT4_LINK_MAX)
 		return -EMLINK;
+	/*
+	 * Return -ENOENT if we've raced with unlink and i_nlink is 0.  Doing
+	 * otherwise has the potential to corrupt the orphan inode list.
+	 */
+	if (inode->i_nlink == 0)
+		return -ENOENT;
 
 retry:
 	handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +