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SubjectRe: [reiserfs-list] [PATCH] reiserfs fix for null bytes in small files
Hi

Chris Mason wrote:

> Hello everyone,
>
> I think Alexander Zarochentcev and I have finally figured out
> cause for null bytes in small reiserfs files. reiserfs stores
> parts of these files packed together in the tree, and the
> packed bytes can shift around as the tree is balanced.
>
> When converting from the packed bytes to a full block, the
> full block is inserted, and the packed bytes are removed. If
> the packed bytes are split between two tree blocks, and then
> merged by a different process balancing the tree, the conversion
> code might remove too many bytes from the file. This creates
> a hole in the file, which is why people see null bytes.
>
> If anyone wants more details, drop a line to me or the reiserfs
> list ;-) This patch against 2.4.1 (will work on any 2.4.1ac or
> 2.4.2pre as well) should fix it, please try it on your
> non-production machines, we are still running it through tests
> here.
>

Just to make things clear:
reiserfs for 2.2 does not have this bug, so there is nothing to fix.

Thanks,
vs


>
> -chris
>
> --- linux/fs/reiserfs/tail_conversion.c.old Thu Feb 15 13:16:47 2001
> +++ linux/fs/reiserfs/tail_conversion.c Thu Feb 15 13:10:23 2001
> @@ -92,7 +92,7 @@
> /* Move bytes from the direct items to the new unformatted node
> and delete them. */
> while (1) {
> - int item_len, first_direct;
> + int tail_size;
>
> /* end_key.k_offset is set so, that we will always have found
> last item of the file */
> @@ -103,13 +103,11 @@
> #ifdef CONFIG_REISERFS_CHECK
> if (!is_direct_le_ih (p_le_ih))
> reiserfs_panic (sb, "vs-14055: direct2indirect: "
> - "direct item expected, found %h", p_le_ih);
> + "direct item expected(%k), found %h",
> + &end_key, p_le_ih);
> #endif
> - if ((le_ih_k_offset (p_le_ih) & (n_blk_size - 1)) == 1)
> - first_direct = 1;
> - else
> - first_direct = 0;
> - item_len = le16_to_cpu (p_le_ih->ih_item_len);
> + tail_size = (le_ih_k_offset (p_le_ih) & (n_blk_size - 1))
> + + ih_item_len(p_le_ih) - 1;
>
> /* we only send the unbh pointer if the buffer is not up to date.
> ** this avoids overwriting good data from writepage() with old data
> @@ -123,7 +121,7 @@
> n_retval = reiserfs_delete_item (th, path, &end_key, inode,
> up_to_date_bh) ;
>
> - if (first_direct && item_len == n_retval)
> + if (tail_size == n_retval)
> // done: file does not have direct items anymore
> break;
>

-
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