diff options
Diffstat (limited to 'fs/ext4/extents_status.h')
| -rw-r--r-- | fs/ext4/extents_status.h | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h index df9628c3ec3b..379b7171c67c 100644 --- a/fs/ext4/extents_status.h +++ b/fs/ext4/extents_status.h @@ -78,6 +78,51 @@ struct ext4_es_stats { struct percpu_counter es_stats_shk_cnt; }; +/* + * Pending cluster reservations for bigalloc file systems + * + * A cluster with a pending reservation is a logical cluster shared by at + * least one extent in the extents status tree with delayed and unwritten + * status and at least one other written or unwritten extent. The + * reservation is said to be pending because a cluster reservation would + * have to be taken in the event all blocks in the cluster shared with + * written or unwritten extents were deleted while the delayed and + * unwritten blocks remained. + * + * The set of pending cluster reservations is an auxiliary data structure + * used with the extents status tree to implement reserved cluster/block + * accounting for bigalloc file systems. The set is kept in memory and + * records all pending cluster reservations. + * + * Its primary function is to avoid the need to read extents from the + * disk when invalidating pages as a result of a truncate, punch hole, or + * collapse range operation. Page invalidation requires a decrease in the + * reserved cluster count if it results in the removal of all delayed + * and unwritten extents (blocks) from a cluster that is not shared with a + * written or unwritten extent, and no decrease otherwise. Determining + * whether the cluster is shared can be done by searching for a pending + * reservation on it. + * + * Secondarily, it provides a potentially faster method for determining + * whether the reserved cluster count should be increased when a physical + * cluster is deallocated as a result of a truncate, punch hole, or + * collapse range operation. The necessary information is also present + * in the extents status tree, but might be more rapidly accessed in + * the pending reservation set in many cases due to smaller size. + * + * The pending cluster reservation set is implemented as a red-black tree + * with the goal of minimizing per page search time overhead. + */ + +struct pending_reservation { + struct rb_node rb_node; + ext4_lblk_t lclu; +}; + +struct ext4_pending_tree { + struct rb_root root; +}; + extern int __init ext4_init_es(void); extern void ext4_exit_es(void); extern void ext4_es_init_tree(struct ext4_es_tree *tree); @@ -182,4 +227,10 @@ extern void ext4_es_unregister_shrinker(struct ext4_sb_info *sbi); extern int ext4_seq_es_shrinker_info_show(struct seq_file *seq, void *v); +extern int __init ext4_init_pending(void); +extern void ext4_exit_pending(void); +extern void ext4_init_pending_tree(struct ext4_pending_tree *tree); +extern void ext4_remove_pending(struct inode *inode, ext4_lblk_t lblk); +extern bool ext4_is_pending(struct inode *inode, ext4_lblk_t lblk); + #endif /* _EXT4_EXTENTS_STATUS_H */ |