This patch lands the last case which needs to be handled by the fsid
change code. Namely, this is the case where a multidisk filesystem has
already undergone at least one successful fsid change i.e all disks
have the METADATA_UUID incompat bit and power failure occurs as another
fsid chind is in progress. When such an event occurs disks should be
split in 2 groups. One of the groups will have both METADATA_UUID and
FSID_CHANGING_V2 flags set coupled with old fsid/metadata_uuid pairs.
The other group of disks will have only METADATA_UUID bit set and their
fsid will be different than the one in disks in the first group. Here
we look at cases:
a) A disk from the first group is scanned first, so fs_devices is
created with stale fsid/metdata_uuid. Then when a disk from the
second group is scanned it needs to first check whether there exists
such an fs_devices that has fsid_change set to true (because it was
created with a disk having the FSID_CHANGING_V2 flag), the
metadata_uuid and fsid of the fsdevices will be different (since it was
created by a disk which already had at least 1 successful fsid change)
and finally the metadata_uuid of the fs_devices will equal that of the
currently scanned disk (because metadata_uuid never really changes).
When the correct fs_devices is found the information from the scanned
disk will replace the current one in fs_devices since the scanned disk
will have higher generation number.
b) A disk from the second group is scanned so fs_devices is created
as usual with differing fsid/metdata_uid. Then when a disk from the
first group is scanned the code detects that it has both
FSID_CHANGING and METADATA_UUID flags set and will scan for fs_devices
that has differing metadata_uuid/fsid and whose metadata_uuid is the
same as that of the scanned device.
Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
---
fs/btrfs/volumes.c | 65 ++++++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 53 insertions(+), 12 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 2c9879a81884..d08667cea189 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -383,7 +383,6 @@ find_fsid(const u8 *fsid, const u8 *metadata_fsid)
ASSERT(fsid);
if (metadata_fsid) {
-
/*
* Handle scanned device having completed its fsid change but
* belonging to a fs_devices that was created by first scanning
@@ -399,6 +398,21 @@ find_fsid(const u8 *fsid, const u8 *metadata_fsid)
return fs_devices;
}
}
+ /*
+ * Handle scanned device having completed its fsid change but
+ * belonging to a fs_devices that was created by a device that
+ * has an outdated pair of fsid/metadata_uuid and CHANGING_FSID
+ * flag set. 6/b
+ */
+ list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+ if (fs_devices->fsid_change &&
+ memcmp(fs_devices->metadata_uuid,
+ fs_devices->fsid, BTRFS_FSID_SIZE) != 0 &&
+ memcmp(metadata_fsid, fs_devices->metadata_uuid,
+ BTRFS_FSID_SIZE) == 0) {
+ return fs_devices;
+ }
+ }
}
/* Handle non-split brain cases */
@@ -808,6 +822,30 @@ static struct btrfs_fs_devices *find_fsid_inprogress(
return NULL;
}
+
+static struct btrfs_fs_devices *find_fsid_changed(
+ struct btrfs_super_block *disk_super)
+{
+ struct btrfs_fs_devices *fs_devices;
+
+ /*
+ * 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. 6/b
+ */
+ 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) {
+ return fs_devices;
+ }
+ }
+
+ return NULL;
+}
/*
* Add new device to list of registered devices
*
@@ -829,17 +867,20 @@ static noinline struct btrfs_device *device_list_add(const char *path,
bool fsid_change_in_progress = (btrfs_super_flags(disk_super) &
BTRFS_SUPER_FLAG_CHANGING_FSID_v2);
- if (fsid_change_in_progress && !has_metadata_uuid) {
- /*
- * When we have an image which has FSID_CHANGE set
- * it might belong to either a filesystem which has
- * disks with completed fsid change or it might belong
- * to fs with no uuid changes in effect, handle both.
- */
- fs_devices = find_fsid_inprogress(disk_super);
- if (!fs_devices)
- fs_devices = find_fsid(disk_super->fsid, NULL);
-
+ if (fsid_change_in_progress) {
+ if (!has_metadata_uuid) {
+ /*
+ * When we have an image which has FSID_CHANGE set
+ * it might belong to either a filesystem which has
+ * disks with completed fsid change or it might belong
+ * to fs with no uuid changes in effect, handle both.
+ */
+ fs_devices = find_fsid_inprogress(disk_super);
+ if (!fs_devices)
+ fs_devices = find_fsid(disk_super->fsid, NULL);
+ } else {
+ fs_devices = find_fsid_changed(disk_super);
+ }
} else if (has_metadata_uuid) {
fs_devices = find_fsid(disk_super->fsid,
disk_super->metadata_uuid);
--
2.7.4
