return ENOENT from ext3_link when racing with unlink

An update from the earlier thread, [PATCH] [RFC] remove ext3 inode from orphan list when link and unlink race

I think this is better than the original idea of trying to handle the race; I've seen that the orphan inode list can get corrupted, but there may well be other implications of the race which haven't yet been exposed. I think it's safer to simply return -ENOENT in this race window, and avoid other potential problems. Anything wrong with this?

Thanks for the comments suggesting this approach in the prior thread.

Thanks,

-Eric

---

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.

Signed-off-by Eric Sandeen <[email protected]>

Index: linux-2.6.19/fs/ext3/namei.c
===================================================================

fs/ext3/namei.c +2 -0

@@ -2191,6 +2191,8 @@ static int ext3_link (struct dentry * ol
 
    if (inode->i_nlink >= EXT3_LINK_MAX)
        return -EMLINK;
+    if (inode->i_nlink == 0)
+        return -ENOENT;
 

retry:

    handle = ext3_journal_start(dir, EXT3_DATA_TRANS_BLOCKS(dir->i_sb) +

Index: linux-2.6.19/fs/ext4/namei.c
===================================================================

fs/ext4/namei.c +2 -0

@@ -2189,6 +2189,8 @@ static int ext4_link (struct dentry * ol
 
    if (inode->i_nlink >= EXT4_LINK_MAX)
        return -EMLINK;
+    if (inode->i_nlink == 0)
+        return -ENOENT;
 

retry:

    handle = ext4_journal_start(dir, EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +

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Peter Staubach (PS) writes:

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Peter Staubach (PS) writes:

PS> Just out of curosity, what keeps i_nlink from going to 0 immediately PS> after the new test is executed?

i_mutex in vfs_link() and vfs_unlink()