On Mon, Jan 20, 2014 at 10:22:17PM -0800, Darrick J. Wong wrote:
> If a client asks us to remap a block in the middle of an extent, we
> potentially have to allocate a fair number of blocks to handle extent
> tree splits. A failure in either of the ext2fs_extent_insert calls
> leaves us with an extent tree that no longer maps the logical block in
> question and everything that came after it! Therefore, try to roll
> back the extent tree changes before returning an error code.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
- Zheng
> ---
> lib/ext2fs/extent.c | 25 ++++++++++++++++++++++---
> 1 file changed, 22 insertions(+), 3 deletions(-)
>
>
> diff --git a/lib/ext2fs/extent.c b/lib/ext2fs/extent.c
> index 2928695..87921e6 100644
> --- a/lib/ext2fs/extent.c
> +++ b/lib/ext2fs/extent.c
> @@ -1438,13 +1438,17 @@ errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle,
> goto done;
> } else {
> __u32 orig_length;
> + blk64_t orig_lblk;
> + struct ext2fs_extent orig_extent;
> + errcode_t r2;
>
> #ifdef DEBUG
> printf("(re/un)mapping in middle of extent\n");
> #endif
> /* need to split this extent; later */
> -
> + orig_lblk = extent.e_lblk;
> orig_length = extent.e_len;
> + orig_extent = extent;
>
> /* shorten pre-split extent */
> extent.e_len = (logical - extent.e_lblk);
> @@ -1456,8 +1460,13 @@ errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle,
> /* insert new extent after current */
> retval = ext2fs_extent_insert(handle,
> EXT2_EXTENT_INSERT_AFTER, &newextent);
> - if (retval)
> + if (retval) {
> + r2 = ext2fs_extent_goto(handle, orig_lblk);
> + if (r2 == 0)
> + ext2fs_extent_replace(handle, 0,
> + &orig_extent);
> goto done;
> + }
> }
> /* add post-split extent */
> extent.e_pblk += extent.e_len + 1;
> @@ -1465,8 +1474,18 @@ errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle,
> extent.e_len = orig_length - extent.e_len - 1;
> retval = ext2fs_extent_insert(handle,
> EXT2_EXTENT_INSERT_AFTER, &extent);
> - if (retval)
> + if (retval) {
> + if (physical) {
> + r2 = ext2fs_extent_goto(handle,
> + newextent.e_lblk);
> + if (r2 == 0)
> + ext2fs_extent_delete(handle, 0);
> + }
> + r2 = ext2fs_extent_goto(handle, orig_lblk);
> + if (r2 == 0)
> + ext2fs_extent_replace(handle, 0, &orig_extent);
> goto done;
> + }
> }
>
> done:
>
> --
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