diff options
| -rw-r--r-- | fs/btrfs/qgroup.h | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h index 1bc64c864b62..a72bf2192757 100644 --- a/fs/btrfs/qgroup.h +++ b/fs/btrfs/qgroup.h @@ -23,6 +23,34 @@ #include "delayed-ref.h" /* + * Btrfs qgroup overview + * + * Btrfs qgroup splits into 3 main part: + * 1) Reserve + * Reserve metadata/data space for incoming operations + * Affect how qgroup limit works + * + * 2) Trace + * Tell btrfs qgroup to trace dirty extents. + * + * Dirty extents including: + * - Newly allocated extents + * - Extents going to be deleted (in this trans) + * - Extents whose owner is going to be modified + * + * This is the main part affects whether qgroup numbers will stay + * consistent. + * Btrfs qgroup can trace clean extents and won't cause any problem, + * but it will consume extra CPU time, it should be avoided if possible. + * + * 3) Account + * Btrfs qgroup will updates its numbers, based on dirty extents traced + * in previous step. + * + * Normally at qgroup rescan and transaction commit time. + */ + +/* * Record a dirty extent, and info qgroup to update quota on it * TODO: Use kmem cache to alloc it. */ |