linux/fs/btrfs/lru_cache.c
Filipe Manana d588adae3b btrfs: add an api to delete a specific entry from the lru cache
In order to replace the open coded name cache in send with the lru cache,
we need an API for the lru cache to delete a specific entry for which we
did a previous lookup. This adds the API for it, and a next patch in the
series will use it.

This patch is part of a larger patchset and the changelog of the last
patch in the series contains a sample performance test and results.
The patches that comprise the patchset are the following:

  btrfs: send: directly return from did_overwrite_ref() and simplify it
  btrfs: send: avoid unnecessary generation search at did_overwrite_ref()
  btrfs: send: directly return from will_overwrite_ref() and simplify it
  btrfs: send: avoid extra b+tree searches when checking reference overrides
  btrfs: send: remove send_progress argument from can_rmdir()
  btrfs: send: avoid duplicated orphan dir allocation and initialization
  btrfs: send: avoid unnecessary orphan dir rbtree search at can_rmdir()
  btrfs: send: reduce searches on parent root when checking if dir can be removed
  btrfs: send: iterate waiting dir move rbtree only once when processing refs
  btrfs: send: initialize all the red black trees earlier
  btrfs: send: genericize the backref cache to allow it to be reused
  btrfs: adapt lru cache to allow for 64 bits keys on 32 bits systems
  btrfs: send: cache information about created directories
  btrfs: allow a generation number to be associated with lru cache entries
  btrfs: add an api to delete a specific entry from the lru cache
  btrfs: send: use the lru cache to implement the name cache
  btrfs: send: update size of roots array for backref cache entries
  btrfs: send: cache utimes operations for directories if possible

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2023-02-13 17:50:36 +01:00

165 lines
3.6 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/mm.h>
#include "lru_cache.h"
#include "messages.h"
/*
* Initialize a cache object.
*
* @cache: The cache.
* @max_size: Maximum size (number of entries) for the cache.
*/
void btrfs_lru_cache_init(struct btrfs_lru_cache *cache, unsigned int max_size)
{
INIT_LIST_HEAD(&cache->lru_list);
mt_init(&cache->entries);
cache->size = 0;
cache->max_size = max_size;
}
static struct btrfs_lru_cache_entry *match_entry(struct list_head *head, u64 key,
u64 gen)
{
struct btrfs_lru_cache_entry *entry;
list_for_each_entry(entry, head, list) {
if (entry->key == key && entry->gen == gen)
return entry;
}
return NULL;
}
/*
* Lookup for an entry in the cache.
*
* @cache: The cache.
* @key: The key of the entry we are looking for.
* @gen: Generation associated to the key.
*
* Returns the entry associated with the key or NULL if none found.
*/
struct btrfs_lru_cache_entry *btrfs_lru_cache_lookup(struct btrfs_lru_cache *cache,
u64 key, u64 gen)
{
struct list_head *head;
struct btrfs_lru_cache_entry *entry;
head = mtree_load(&cache->entries, key);
if (!head)
return NULL;
entry = match_entry(head, key, gen);
if (entry)
list_move_tail(&entry->lru_list, &cache->lru_list);
return entry;
}
/*
* Remove an entry from the cache.
*
* @cache: The cache to remove from.
* @entry: The entry to remove from the cache.
*
* Note: this also frees the memory used by the entry.
*/
void btrfs_lru_cache_remove(struct btrfs_lru_cache *cache,
struct btrfs_lru_cache_entry *entry)
{
struct list_head *prev = entry->list.prev;
ASSERT(cache->size > 0);
ASSERT(!mtree_empty(&cache->entries));
list_del(&entry->list);
list_del(&entry->lru_list);
if (list_empty(prev)) {
struct list_head *head;
/*
* If previous element in the list entry->list is now empty, it
* means it's a head entry not pointing to any cached entries,
* so remove it from the maple tree and free it.
*/
head = mtree_erase(&cache->entries, entry->key);
ASSERT(head == prev);
kfree(head);
}
kfree(entry);
cache->size--;
}
/*
* Store an entry in the cache.
*
* @cache: The cache.
* @entry: The entry to store.
*
* Returns 0 on success and < 0 on error.
*/
int btrfs_lru_cache_store(struct btrfs_lru_cache *cache,
struct btrfs_lru_cache_entry *new_entry,
gfp_t gfp)
{
const u64 key = new_entry->key;
struct list_head *head;
int ret;
head = kmalloc(sizeof(*head), gfp);
if (!head)
return -ENOMEM;
ret = mtree_insert(&cache->entries, key, head, gfp);
if (ret == 0) {
INIT_LIST_HEAD(head);
list_add_tail(&new_entry->list, head);
} else if (ret == -EEXIST) {
kfree(head);
head = mtree_load(&cache->entries, key);
ASSERT(head != NULL);
if (match_entry(head, key, new_entry->gen) != NULL)
return -EEXIST;
list_add_tail(&new_entry->list, head);
} else if (ret < 0) {
kfree(head);
return ret;
}
if (cache->size == cache->max_size) {
struct btrfs_lru_cache_entry *lru_entry;
lru_entry = list_first_entry(&cache->lru_list,
struct btrfs_lru_cache_entry,
lru_list);
btrfs_lru_cache_remove(cache, lru_entry);
}
list_add_tail(&new_entry->lru_list, &cache->lru_list);
cache->size++;
return 0;
}
/*
* Empty a cache.
*
* @cache: The cache to empty.
*
* Removes all entries from the cache.
*/
void btrfs_lru_cache_clear(struct btrfs_lru_cache *cache)
{
struct btrfs_lru_cache_entry *entry;
struct btrfs_lru_cache_entry *tmp;
list_for_each_entry_safe(entry, tmp, &cache->lru_list, lru_list)
btrfs_lru_cache_remove(cache, entry);
ASSERT(cache->size == 0);
ASSERT(mtree_empty(&cache->entries));
}