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authorNikolay Borisov <nborisov@suse.com>2018-10-30 16:43:27 +0200
committerDavid Sterba <dsterba@suse.com>2018-12-17 14:51:38 +0100
commit7a62d0f07377b51a9033eb12fa537c264bcba3e5 (patch)
treed6952b42c6f143a0dd48fc27f625483079d070ee /fs/btrfs/volumes.c
parentd1a63002829a4d8014de20dc141b404cc808405e (diff)
btrfs: Handle one more split-brain scenario during fsid change
This commit continues hardening the scanning code to handle cases where power loss could have caused disks in a multi-disk filesystem to be in inconsistent state. Namely handle the situation that can occur when some of the disks in multi-disk fs have completed their fsid change i.e they have METADATA_UUID incompat flag set, have cleared the CHANGING_FSID_V2 flag and their fsid/metadata_uuid are different. At the same time the other half of the disks will have their fsid/metadata_uuid unchanged and will only have CHANGING_FSID_V2 flag. This is handled by introducing code in the scan path which: a) Handles the case when a device with CHANGING_FSID_V2 flag is scanned and as a result btrfs_fs_devices is created with matching fsid/metdata_uuid. Subsequently, when a device with completed fsid change is scanned it will detect this via the new code in find_fsid i.e that such an fs_devices exist that fsid_change flag is set to true, it's metadata_uuid/fsid match and the metadata_uuid of the scanned device matches that of the fs_devices. In this case, it's important to note that the devices which has its fsid change completed will have a higher generation number than the device with FSID_CHANGING_V2 flag set, so its superblock block will be used during mount. To prevent an assertion triggering because the sb used for mounting will have differing fsid/metadata_uuid than the ones in the fs_devices struct also add code in device_list_add which overwrites the values in fs_devices. b) Alternatively we can end up with a device that completed its fsid change be scanned first which will create the respective btrfs_fs_devices struct with differing fsid/metadata_uuid. In this case when a device with FSID_CHANGING_V2 flag set is scanned it will call the newly added find_fsid_inprogress function which will return the correct fs_devices. 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.c77
1 files changed, 73 insertions, 4 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 13bb44194c56..ce14ce068a84 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -389,6 +389,25 @@ static noinline struct btrfs_fs_devices *find_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
+ * a device which didn't have its fsid/metadata_uuid changed
+ * at all and the CHANGING_FSID_V2 flag set.
+ */
+ list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+ if (fs_devices->fsid_change &&
+ memcmp(metadata_fsid, fs_devices->fsid,
+ BTRFS_FSID_SIZE) == 0 &&
+ memcmp(fs_devices->fsid, fs_devices->metadata_uuid,
+ BTRFS_FSID_SIZE) == 0) {
+ return fs_devices;
+ }
+ }
+ }
+
+ /* Handle non-split brain cases */
list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
if (metadata_fsid) {
if (memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE) == 0
@@ -775,6 +794,27 @@ error_brelse:
}
/*
+ * Handle scanned device having its CHANGING_FSID_V2 flag set and the fs_devices
+ * being created with a disk that has already completed its fsid change.
+ */
+static struct btrfs_fs_devices *find_fsid_inprogress(
+ struct btrfs_super_block *disk_super)
+{
+ struct btrfs_fs_devices *fs_devices;
+
+ 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->fsid,
+ BTRFS_FSID_SIZE) == 0 && !fs_devices->fsid_change) {
+ return fs_devices;
+ }
+ }
+
+ return NULL;
+}
+
+/*
* Add new device to list of registered devices
*
* Returns:
@@ -786,7 +826,7 @@ static noinline struct btrfs_device *device_list_add(const char *path,
bool *new_device_added)
{
struct btrfs_device *device;
- struct btrfs_fs_devices *fs_devices;
+ struct btrfs_fs_devices *fs_devices = NULL;
struct rcu_string *name;
u64 found_transid = btrfs_super_generation(disk_super);
u64 devid = btrfs_stack_device_id(&disk_super->dev_item);
@@ -795,10 +835,24 @@ 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 (has_metadata_uuid)
- fs_devices = find_fsid(disk_super->fsid, disk_super->metadata_uuid);
- else
+ if (fsid_change_in_progress && !has_metadata_uuid) {
+ /*
+ * When we have an image which has CHANGING_FSID_V2 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 if (has_metadata_uuid) {
+ fs_devices = find_fsid(disk_super->fsid,
+ disk_super->metadata_uuid);
+ } else {
fs_devices = find_fsid(disk_super->fsid, NULL);
+ }
+
if (!fs_devices) {
if (has_metadata_uuid)
@@ -820,6 +874,21 @@ static noinline struct btrfs_device *device_list_add(const char *path,
mutex_lock(&fs_devices->device_list_mutex);
device = find_device(fs_devices, devid,
disk_super->dev_item.uuid);
+
+ /*
+ * If this disk has been pulled into an fs devices created by
+ * a device which had the CHANGING_FSID_V2 flag then replace the
+ * metadata_uuid/fsid values of the fs_devices.
+ */
+ if (has_metadata_uuid && fs_devices->fsid_change &&
+ found_transid > fs_devices->latest_generation) {
+ memcpy(fs_devices->fsid, disk_super->fsid,
+ BTRFS_FSID_SIZE);
+ memcpy(fs_devices->metadata_uuid,
+ disk_super->metadata_uuid, BTRFS_FSID_SIZE);
+
+ fs_devices->fsid_change = false;
+ }
}
if (!device) {