| Message ID | 20200110121135.7386-4-nborisov@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | More split-brain fixes for metadata uuid feature | expand |
On 1/10/20 7:11 AM, Nikolay Borisov wrote: > 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") > Reported-by: Su Yue <Damenly_Su@gmx.com> > Signed-off-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Thanks, Josef
On Fri, Jan 10, 2020 at 02:11:34PM +0200, Nikolay Borisov wrote: > list_for_each_entry(fs_devices, &fs_uuids, fs_list) { > - 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) { > + bool changed_fsdevices = > + 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; > + > + bool unchanged_fsdevices = > + memcmp(fs_devices->metadata_uuid, fs_devices->fsid, > + BTRFS_FSID_SIZE) == 0 && > + memcmp(fs_devices->fsid, disk_super->metadata_uuid, BTRFS_FSID_SIZE) == 0; > + if (changed_fsdevices || unchanged_fsdevices) > return fs_devices; This is ugly, I've converted it to if (memcmp) and dropped the variables.
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 90e5ed5f5364..7739d40939bf 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -709,17 +709,26 @@ 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) { - 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) { + bool changed_fsdevices = + 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; + + bool unchanged_fsdevices = + memcmp(fs_devices->metadata_uuid, fs_devices->fsid, + BTRFS_FSID_SIZE) == 0 && + memcmp(fs_devices->fsid, disk_super->metadata_uuid, BTRFS_FSID_SIZE) == 0; + if (changed_fsdevices || unchanged_fsdevices) return fs_devices; - } } return NULL;
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") Reported-by: Su Yue <Damenly_Su@gmx.com> Signed-off-by: Nikolay Borisov <nborisov@suse.com> --- fs/btrfs/volumes.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) -- 2.17.1 find_fsid_changed