Snapshot deletion performance has been reported to be an issue, so this patch series should address that.
The important optimization relies on the fact that if an extent/dirent/xattr exists, a version of that inode must exist in that specific snapshot. We can make use of that to avoid a lot of scanning. Previously only fsck relied on this, so it would spit out a warning and correct the issue in its in memory data structures if this occurred. Now, it's turned into a proper fsck_err() with on-disk repair if detected. We also want some additional safety with this: if snapshot deletion ever screws up and doesn't delete all the keys it was supposed to, we want to be able to automatically repair. So there's a new on disk format version with an incompatible (i.e. must be expliticly enabled) feature, where we never delete snapshot keys - we just mark them as deleted. This allows fsck to differentiate between "key for deleted snapshot, I know how to repair this" vs. "key for missing snapshot, we're not sure what happened and someone should probably take a look". And snapshot deletion status is now present in sysfs, currently with btree and position in that btree. We do have per-snapshot-id accounting, so it might be possible to turn that into a proper progress indicator later. Kent Overstreet (8): bcachefs: snapshot delete progress indicator bcachefs: Add comments for inode snapshot requirements bcachefs: kill inode_walker_entry.snapshot bcachefs: BCH_FSCK_ERR_snapshot_key_missing_inode_snapshot bcachefs: Skip unrelated snapshot trees in snapshot deletion bcachefs: BCH_SNAPSHOT_DELETED -> BCH_SNAPSHOT_WILL_DELETE bcachefs: bcachefs_metadata_version_snapshot_deletion_v2 bcachefs: delete_dead_snapshot_keys_v2() fs/bcachefs/bcachefs.h | 3 +- fs/bcachefs/bcachefs_format.h | 3 +- fs/bcachefs/fsck.c | 78 ++++--- fs/bcachefs/io_write.c | 6 + fs/bcachefs/sb-errors_format.h | 4 +- fs/bcachefs/snapshot.c | 389 +++++++++++++++++++++++++-------- fs/bcachefs/snapshot.h | 32 ++- fs/bcachefs/snapshot_format.h | 4 +- fs/bcachefs/snapshot_types.h | 56 +++++ fs/bcachefs/subvolume.c | 2 - fs/bcachefs/subvolume.h | 3 - fs/bcachefs/subvolume_types.h | 27 --- fs/bcachefs/super.c | 1 + fs/bcachefs/sysfs.c | 5 + fs/bcachefs/xattr.c | 5 + 15 files changed, 445 insertions(+), 173 deletions(-) create mode 100644 fs/bcachefs/snapshot_types.h -- 2.49.0
