diff options
Diffstat (limited to 'fs/btrfs/delayed-ref.h')
| -rw-r--r-- | fs/btrfs/delayed-ref.h | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h index 085f30968aba..352921e76c74 100644 --- a/fs/btrfs/delayed-ref.h +++ b/fs/btrfs/delayed-ref.h @@ -202,7 +202,15 @@ struct btrfs_delayed_ref_root { /* head ref rbtree */ struct rb_root_cached href_root; - /* Track dirty extent records. */ + /* + * Track dirty extent records. + * The keys correspond to the logical address of the extent ("bytenr") + * right shifted by fs_info->sectorsize_bits. This is both to get a more + * dense index space (optimizes xarray structure) and because indexes in + * xarrays are of "unsigned long" type, meaning they are 32 bits wide on + * 32 bits platforms, limiting the extent range to 4G which is too low + * and makes it unusable (truncated index values) on 32 bits platforms. + */ struct xarray dirty_extents; /* this spin lock protects the rbtree and the entries inside */ |