diff options
Diffstat (limited to 'fs/btrfs/lru_cache.h')
| -rw-r--r-- | fs/btrfs/lru_cache.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/fs/btrfs/lru_cache.h b/fs/btrfs/lru_cache.h index 44a7b41236ce..7a255cd2958e 100644 --- a/fs/btrfs/lru_cache.h +++ b/fs/btrfs/lru_cache.h @@ -17,6 +17,18 @@ struct btrfs_lru_cache_entry { struct list_head lru_list; u64 key; + /* + * The maple tree uses unsigned long type for the keys, which is 32 bits + * on 32 bits systems, and 64 bits on 64 bits systems. So if we want to + * use something like inode numbers as keys, which are always a u64, we + * have to deal with this in a special way - we store the key in the + * entry itself, as a u64, and the values inserted into the maple tree + * are linked lists of entries - so in case we are on a 64 bits system, + * that list always has a single entry, while on 32 bits systems it + * may have more than one, with each entry having the same value for + * their lower 32 bits of the u64 key. + */ + struct list_head list; }; struct btrfs_lru_cache { |