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btrfs: add members to fs_devices to track fsid changes
In order to gracefully handle split-brain scenario during fsid change (which are very unlikely, yet possible), two more pieces of information will be necessary: 1. The highest generation number among all devices registered to a particular btrfs_fs_devices 2. A boolean flag whether a given btrfs_fs_devices was created by a device which had the FSID_CHANGING_V2 flag set. This is a preparatory patch and just introduces the variables as well as code which sets them, their actual use is going to happen in a later patch. Signed-off-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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2 changed files with 13 additions and 1 deletions
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@ -792,6 +792,8 @@ static noinline struct btrfs_device *device_list_add(const char *path,
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u64 devid = btrfs_stack_device_id(&disk_super->dev_item);
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bool has_metadata_uuid = (btrfs_super_incompat_flags(disk_super) &
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BTRFS_FEATURE_INCOMPAT_METADATA_UUID);
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bool fsid_change_in_progress = (btrfs_super_flags(disk_super) &
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BTRFS_SUPER_FLAG_CHANGING_FSID_V2);
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if (has_metadata_uuid)
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fs_devices = find_fsid(disk_super->fsid, disk_super->metadata_uuid);
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@ -805,6 +807,8 @@ static noinline struct btrfs_device *device_list_add(const char *path,
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else
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fs_devices = alloc_fs_devices(disk_super->fsid, NULL);
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fs_devices->fsid_change = fsid_change_in_progress;
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if (IS_ERR(fs_devices))
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return ERR_CAST(fs_devices);
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@ -940,8 +944,11 @@ static noinline struct btrfs_device *device_list_add(const char *path,
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* it back. We need it to pick the disk with largest generation
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* (as above).
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*/
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if (!fs_devices->opened)
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if (!fs_devices->opened) {
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device->generation = found_transid;
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fs_devices->latest_generation = max_t(u64, found_transid,
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fs_devices->latest_generation);
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}
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fs_devices->total_devices = btrfs_super_num_devices(disk_super);
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@ -211,6 +211,7 @@ BTRFS_DEVICE_GETSET_FUNCS(bytes_used);
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struct btrfs_fs_devices {
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u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */
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u8 metadata_uuid[BTRFS_FSID_SIZE];
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bool fsid_change;
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struct list_head fs_list;
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u64 num_devices;
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@ -219,6 +220,10 @@ struct btrfs_fs_devices {
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u64 missing_devices;
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u64 total_rw_bytes;
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u64 total_devices;
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/* Highest generation number of seen devices */
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u64 latest_generation;
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struct block_device *latest_bdev;
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/* all of the devices in the FS, protected by a mutex
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