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authorNikolay Borisov <nborisov@suse.com>2020-01-10 14:11:34 +0200
committerDavid Sterba <dsterba@suse.com>2020-01-23 17:24:38 +0100
commit05840710149c7d1a78ea85a2db5723f706e97d8f (patch)
tree926e216b113647bdc2a5126214718cc9312ef1c1 /fs/btrfs/volumes.c
parentc6730a0e5778bf2d83189f97ab5e3efe61f6aad1 (diff)
btrfs: Handle another split brain scenario with metadata uuid feature
There is one more cases which isn't handled by the original metadata uuid work. Namely, when a filesystem has METADATA_UUID incompat bit and the user decides to change the FSID to the original one e.g. have metadata_uuid and fsid match. In case of power failure while this operation is in progress we could end up in a situation where some of the disks have the incompat bit removed and the other half have both METADATA_UUID_INCOMPAT and FSID_CHANGING_IN_PROGRESS flags. This patch handles the case where a disk that has successfully changed its FSID such that it equals METADATA_UUID is scanned first. Subsequently when a disk with both METADATA_UUID_INCOMPAT/FSID_CHANGING_IN_PROGRESS flags is scanned find_fsid_changed won't be able to find an appropriate btrfs_fs_devices. This is done by extending find_fsid_changed to correctly find btrfs_fs_devices whose metadata_uuid/fsid are the same and they match the metadata_uuid of the currently scanned device. Fixes: cc5de4e70256 ("btrfs: Handle final split-brain possibility during fsid change") Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reported-by: Su Yue <Damenly_Su@gmx.com> Signed-off-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/volumes.c')
-rw-r--r--fs/btrfs/volumes.c17
1 files changed, 14 insertions, 3 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index d48274451452..7a30dd8ffdb5 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -710,17 +710,28 @@ static struct btrfs_fs_devices *find_fsid_changed(
/*
* Handles the case where scanned device is part of an fs that had
* multiple successful changes of FSID but curently device didn't
- * observe it. Meaning our fsid will be different than theirs.
+ * observe it. Meaning our fsid will be different than theirs. We need
+ * to handle two subcases :
+ * 1 - The fs still continues to have different METADATA/FSID uuids.
+ * 2 - The fs is switched back to its original FSID (METADATA/FSID
+ * are equal).
*/
list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+ /* Changed UUIDs */
if (memcmp(fs_devices->metadata_uuid, fs_devices->fsid,
BTRFS_FSID_SIZE) != 0 &&
memcmp(fs_devices->metadata_uuid, disk_super->metadata_uuid,
BTRFS_FSID_SIZE) == 0 &&
memcmp(fs_devices->fsid, disk_super->fsid,
- BTRFS_FSID_SIZE) != 0) {
+ BTRFS_FSID_SIZE) != 0)
+ return fs_devices;
+
+ /* Unchanged UUIDs */
+ if (memcmp(fs_devices->metadata_uuid, fs_devices->fsid,
+ BTRFS_FSID_SIZE) == 0 &&
+ memcmp(fs_devices->fsid, disk_super->metadata_uuid,
+ BTRFS_FSID_SIZE) == 0)
return fs_devices;
- }
}
return NULL;