On Tue, Sep 20, 2016 at 10:50:39AM -0500, Eric Sandeen wrote:
> Zorro reported that when making multiple copies of a V5
> filesystem with xfs_copy while generating new UUIDs, all
> but the first copy were corrupt.
>
> Upon inspection, the corruption was related to incorrect UUIDs;
> the original UUID, as stamped into every metadata structure,
> was not preserved in the sb_meta_uuid field of the superblock
> on any but the first copy.
>
> This happened because sb_update_uuid was using the UUID present in
> the ag_hdr structure as the unchanging meta-uuid which is to match
> existing structures, but it also /updates/ that UUID with the
> new identifying UUID present in tcarg. So the newly-generated
> UUIDs moved transitively from tcarg->uuid to ag_hdr->xfs_sb->sb_uuid
> to ag_hdr->xfs_sb->sb_meta_uuid each time the function got called.
>
> Fix this by looking instead to the unchanging, original UUID
> present in the xfs_sb_t we are given, which reflects the original
> filesystem's metadata UUID, and copy /that/ UUID into each target
> filesystem's meta_uuid field.
>
> Most of this patch is changing comments and re-ordering tests
> to match; the functional change is to simply use the *sb rather
> than the *ag_hdr to identify the proper metadata UUID.
>
> Reported-by: Zorro Lang <zlang@xxxxxxxxxx>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
I can't reproduce that bug again after merge this patch. V4 and V5
XFS all test passed, different block size test passed too.
I didn't do regression test for this patch.
Thanks,
Zorro
>
>
> diff --git a/copy/xfs_copy.c b/copy/xfs_copy.c
> index 3c8998c..d8edfdd 100644
> --- a/copy/xfs_copy.c
> +++ b/copy/xfs_copy.c
> @@ -494,27 +494,29 @@ write_wbuf(void)
>
> void
> sb_update_uuid(
> - xfs_sb_t *sb,
> - ag_header_t *ag_hdr,
> - thread_args *tcarg)
> + xfs_sb_t *sb, /* Original fs superblock */
> + ag_header_t *ag_hdr, /* AG hdr to update for this copy */
> + thread_args *tcarg) /* Args for this thread, with UUID */
> {
> /*
> * If this filesystem has CRCs, the original UUID is stamped into
> - * all metadata. If we are changing the UUID in the copy, we need
> - * to copy the original UUID into the meta_uuid slot and set the
> - * set the incompat flag if that hasn't already been done.
> + * all metadata. If we don't have an existing meta_uuid field in the
> + * the original filesystem and we are changing the UUID in this copy,
> + * we must copy the original sb_uuid to the sb_meta_uuid slot and set
> + * the incompat flag for the feature on this copy.
> */
> - if (!uuid_equal(&tcarg->uuid, &ag_hdr->xfs_sb->sb_uuid) &&
> - xfs_sb_version_hascrc(sb) && !xfs_sb_version_hasmetauuid(sb)) {
> + if (xfs_sb_version_hascrc(sb) && !xfs_sb_version_hasmetauuid(sb) &&
> + !uuid_equal(&tcarg->uuid, &sb->sb_uuid)) {
> __be32 feat;
>
> feat = be32_to_cpu(ag_hdr->xfs_sb->sb_features_incompat);
> feat |= XFS_SB_FEAT_INCOMPAT_META_UUID;
> ag_hdr->xfs_sb->sb_features_incompat = cpu_to_be32(feat);
> platform_uuid_copy(&ag_hdr->xfs_sb->sb_meta_uuid,
> - &ag_hdr->xfs_sb->sb_uuid);
> + &sb->sb_uuid);
> }
>
> + /* Copy the (possibly new) fs-identifier UUID into sb_uuid */
> platform_uuid_copy(&ag_hdr->xfs_sb->sb_uuid, &tcarg->uuid);
>
> /* We may have changed the UUID, so update the superblock CRC */
>
>
> --
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