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Message-ID: <51AE61FB.8080402@redhat.com>
Date: Tue, 04 Jun 2013 16:54:03 -0500
From: Eric Sandeen <sandeen@...hat.com>
To: David Jeffery <djeffery@...hat.com>
CC: linux-ext4@...r.kernel.org
Subject: Re: [PATCH] e2fsck: detect invalid extents at the end of an extent-block
On 4/3/13 2:08 PM, David Jeffery wrote:
> e2fsck does not detect extents which are outside their location in the
> extent tree. This can result in a bad extent at the end of an extent-block
> not being detected.
>
> From a part of a dump_extents output:
>
> 1/ 2 37/ 68 143960 - 146679 123826181 2720
> 2/ 2 1/ 2 143960 - 146679 123785816 - 123788535 2720
> 2/ 2 2/ 2 146680 - 147583 123788536 - 123789439 904 Uninit <-bad extent
> 1/ 2 38/ 68 146680 - 149391 123826182 2712
> 2/ 2 1/ 2 146680 - 147583 18486 - 19389 904
> 2/ 2 2/ 2 147584 - 149391 123789440 - 123791247 1808
>
> e2fsck does not detect this bad extent which both overlaps another, valid
> extent, and is invalid by being beyond the end of the extent above it in
> the tree.
>
> This patch modifies e2fsck to detect this invalid extent and remove it.
>
> Signed-off-by: David Jeffery <djeffery@...hat.com>
> ---
> e2fsck/pass1.c | 13 +++++++++----
> e2fsck/problem.c | 6 ++++++
> e2fsck/problem.h | 1 +
> 3 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
> index a20b57b..198e9a0 100644
> --- a/e2fsck/pass1.c
> +++ b/e2fsck/pass1.c
> @@ -1848,7 +1848,7 @@ void e2fsck_clear_inode(e2fsck_t ctx, ext2_ino_t ino,
>
> static void scan_extent_node(e2fsck_t ctx, struct problem_context *pctx,
> struct process_block_struct *pb,
> - blk64_t start_block,
> + blk64_t start_block, blk64_t end_block,
> ext2_extent_handle_t ehandle)
> {
> struct ext2fs_extent extent;
> @@ -1891,6 +1891,9 @@ static void scan_extent_node(e2fsck_t ctx, struct problem_context *pctx,
> problem = PR_1_EXTENT_BAD_START_BLK;
> else if (extent.e_lblk < start_block)
> problem = PR_1_OUT_OF_ORDER_EXTENTS;
> + else if (end_block &&
> + (extent.e_lblk + extent.e_len) > end_block)
> + problem = PR_1_EXTENT_END_OUT_OF_BOUNDS;
thinking out loud; let's say e_lblk is 10 and len is 10. So the
extent covers blocks 10->19, and e_lbk + e_len is 20, though
the last block in the range is 19.
But you pass in the same value (lblk + len) as "last block" so I guess
it matches up, it just requires some thought.
It might be better to do this in the caller:
lblk_end = extent.e_lblk + extent.e_len - 1;
and this in the test:
else if (end_block &&
(extent.e_lblk + extent.e_len - 1) > end_block)
just so that "end_block" really is the end block?
> else if (is_leaf && extent.e_len == 0)
> problem = PR_1_EXTENT_LENGTH_ZERO;
> else if (is_leaf &&
> @@ -1937,10 +1940,11 @@ fix_problem_now:
> }
>
> if (!is_leaf) {
> - blk64_t lblk;
> + blk64_t lblk, lblk_end;
>
> blk = extent.e_pblk;
> lblk = extent.e_lblk;
> + lblk_end = extent.e_lblk + extent.e_len;
maybe extent.e_lblk + extent.e_len - 1 ?
> pctx->errcode = ext2fs_extent_get(ehandle,
> EXT2_EXTENT_DOWN, &extent);
> if (pctx->errcode) {
> @@ -1965,7 +1969,8 @@ fix_problem_now:
> if (fix_problem(ctx, problem, pctx))
> ext2fs_extent_fix_parents(ehandle);
> }
> - scan_extent_node(ctx, pctx, pb, extent.e_lblk, ehandle);
> + scan_extent_node(ctx, pctx, pb, extent.e_lblk,
> + lblk_end, ehandle);
> if (pctx->errcode)
> return;
> pctx->errcode = ext2fs_extent_get(ehandle,
> @@ -2084,7 +2089,7 @@ static void check_blocks_extents(e2fsck_t ctx, struct problem_context *pctx,
> ctx->extent_depth_count[info.max_depth]++;
> }
>
> - scan_extent_node(ctx, pctx, pb, 0, ehandle);
> + scan_extent_node(ctx, pctx, pb, 0, 0, ehandle);
Other than the above nitpick, I think this does what it advertises, so:
Reviewed-by: Eric Sandeen <sandeen@...hat.com>
Thanks,
-Eric
> if (pctx->errcode &&
> fix_problem(ctx, PR_1_EXTENT_ITERATE_FAILURE, pctx)) {
> pb->num_blocks = 0;
> diff --git a/e2fsck/problem.c b/e2fsck/problem.c
> index 76bc1d5..b0a6e19 100644
> --- a/e2fsck/problem.c
> +++ b/e2fsck/problem.c
> @@ -1008,6 +1008,12 @@ static struct e2fsck_problem problem_table[] = {
> "Logical start %b does not match logical start %c at next level. "),
> PROMPT_FIX, 0 },
>
> + /* Extent end is out of bounds for the tree */
> + { PR_1_EXTENT_END_OUT_OF_BOUNDS,
> + N_("@i %i, end of extent exceeds allowed value\n\t(logical @b %c, physical @b %b, len %N)\n"),
> + PROMPT_CLEAR, 0 },
> +
> +
> /* Pass 1b errors */
>
> /* Pass 1B: Rescan for duplicate/bad blocks */
> diff --git a/e2fsck/problem.h b/e2fsck/problem.h
> index d2b6df4..fcdc1a1 100644
> --- a/e2fsck/problem.h
> +++ b/e2fsck/problem.h
> @@ -589,6 +589,7 @@ struct problem_context {
> /* Index start doesn't match start of next extent down */
> #define PR_1_EXTENT_INDEX_START_INVALID 0x01006D
>
> +#define PR_1_EXTENT_END_OUT_OF_BOUNDS 0x01006E
> /*
> * Pass 1b errors
> */
> --
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