Re: [PATCH] Fix bug in ext3 htree rename: doesn't delete old name, leaves ino with bad nlink

["Theodore Ts'o" <tytso@mit.edu>]

On Wed, Nov 06, 2002 at 12:25:00AM -0800, chrisl@vmware.com wrote:
> This should fix the ext3 htree rename problem. Please try it again.

I've looked over the patch, and I've got some comments....

>         handle = ext3_journal_start(old_dir, 2 * EXT3_DATA_TRANS_BLOCKS +
> -                                       EXT3_INDEX_EXTRA_TRANS_BLOCKS + 2);
> +                                       EXT3_INDEX_EXTRA_TRANS_BLOCKS + 3);

There's no need to increase the number of blocks that might need to be
dirtied; if ext3_delete_entry() can't find the missing entry, it won't
dirty the block, so the number of blocks that might need to modified
remains constant.

> -       ext3_delete_entry(handle, old_dir, old_de, old_bh);
> +       retval = ext3_delete_entry(handle, old_dir, old_de, old_bh);
> +       if (retval == -ENOENT) {
> +               /*
> +                * old_de can be moved during ext3_add_entry.
> +                */
> +               struct buffer_head * old_bh2;
> +               struct ext3_dir_entry_2 * old_de2;
> +               old_bh2 = ext3_find_entry (old_dentry, &old_de2);
> +               if (old_bh2) {
> +                       retval = ext3_delete_entry(handle, old_dir, old_de2,
> +                                                  old_bh2);
> +                       brelse(old_bh2);
> +               } else {
> +                       ext3_warning(old_dir->i_sb, "ext3_rename",
> +                                    "Deleting old file not found (%lu), %d",
> +                                    old_dir->i_ino, old_dir->i_nlink);
> +               }
>  
> +       }

Simply retrying the ext3_delete_entry() isn't sufficient, since
another ext3_add_entry() could move the directory entry again while
you're reading in the blocks as part of ext3_find_entry().  OK, that
would be pretty rare, since enough other directory adds would have
to fill up enough that another split could happen, but *is* possible.
(Surely our scheduler isn't that unfair....)

Probably a better thing to do is use a while loop, and retry as long
(a) ext3_delete_entry fails, and (b) old_dir->i_version has changed.
In practice this will probably never happen, but I'll feel better with
that change.

Anyway, I plan to make these two changes to your patch, and then
submit it to Linus.

						- Ted