commit cbca895541facb3a1a00fd0fe6614301a64c0e3a Author: Eric Sandeen Date: Fri Sep 23 09:16:52 2016 +1000 xfs_copy: Fix meta UUID handling on multiple copies 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-and-tested-by: Zorro Lang Signed-off-by: Eric Sandeen Reviewed-by: Dave Chinner Signed-off-by: Dave Chinner diff --git a/copy/xfs_copy.c b/copy/xfs_copy.c index 3c8998c..22ded6b 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 */