Theodore Ts'o wrote:
> In the case where we ext2fs_extent_set_bmap() is replacing the block
> mapping at the beginning of an already-existing extent, insert a new
> extent if necessary before shrinking an existing extent, to avoid data
> loss if the disk is full.
>
> This mostly addresses the problem described in Red Hat Bugzilla's
> statistics are still wrong, but at least the files on the filesystem
> are not corrupted. If there is a failure during the
> inode_scan_and_fix pass, the simplest thing to do may be to tell the
> user to run e2fsck -fy.
>
> Addresses-Red-Hat-Bug: #510379
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> ---
> lib/ext2fs/extent.c | 44 ++++++++++++++++++++++++++++++++------------
> 1 files changed, 32 insertions(+), 12 deletions(-)
>
> diff --git a/lib/ext2fs/extent.c b/lib/ext2fs/extent.c
> index 4a4fd2c..2f280ea 100644
> --- a/lib/ext2fs/extent.c
> +++ b/lib/ext2fs/extent.c
> @@ -1270,24 +1270,44 @@ again:
> #ifdef DEBUG
> printf("(re/un)mapping first block in extent\n");
> #endif
> + if (physical) {
> + retval = ext2fs_extent_get(handle,
> + EXT2_EXTENT_PREV_LEAF,
> + &extent);
> + if (extent.e_flags & EXT2_EXTENT_FLAGS_UNINIT)
> + extent_uninit = 1;
> + if (retval == EXT2_ET_EXTENT_NO_PREV) {
> + retval = ext2fs_extent_insert(handle,
> + 0, &newextent);
> + } else if (retval)
> + goto done;
A lot of this is cut & paste from "mapping unmapped logical block" - at
some point we should probably factor out into helpers, but fine for now.
A little comment here about extent merging may be helpful just to guide
the reader; it's a lot of conditionals to eyeball - not so difficult in
the end, but not all that conducive to a quick skim either.
Aside from those nitpicks (and the now-extraneous again: goto target)
this look fine to me, thanks.
-Eric
> + else if ((logical == extent.e_lblk + extent.e_len) &&
> + (physical == extent.e_pblk + extent.e_len) &&
> + (new_uninit == extent_uninit) &&
> + ((int) extent.e_len < max_len-1)) {
> + extent.e_len++;
> + retval = ext2fs_extent_replace(handle, 0,
> + &extent);
> + } else {
> + retval = ext2fs_extent_insert(handle,
> + EXT2_EXTENT_INSERT_AFTER, &newextent);
> + }
> + if (retval)
> + goto done;
> + }
> + retval = ext2fs_extent_fix_parents(handle);
> + if (retval)
> + goto done;
> + retval = ext2fs_extent_get(handle, EXT2_EXTENT_NEXT_LEAF,
> + &extent);
> + if (retval)
> + goto done;
> extent.e_pblk++;
> extent.e_lblk++;
> extent.e_len--;
> retval = ext2fs_extent_replace(handle, 0, &extent);
> if (retval)
> goto done;
> - if (physical) {
> - /*
> - * We've removed the old block, now rely on
> - * the optimized hueristics for adding a new
> - * mapping with appropriate merging if necessary.
> - */
> - goto again;
> - } else {
> - retval = ext2fs_extent_fix_parents(handle);
> - if (retval)
> - goto done;
> - }
> } else {
> __u32 orig_length;
>
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