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mm/zswap: invalidate zswap entry when swap entry free 

During testing I found there are some times the zswap_writeback_entry()
return -ENOMEM, which is not we expected:

bpftrace -e 'kr:zswap_writeback_entry {@[(int32)retval]=count()}'
@[-12]: 1563
@[0]: 277221

The reason is that __read_swap_cache_async() return NULL because
swapcache_prepare() failed.  The reason is that we won't invalidate zswap
entry when swap entry freed to the per-cpu pool, these zswap entries are
still on the zswap tree and lru list.

This patch moves the invalidation ahead to when swap entry freed to the
per-cpu pool, since there is no any benefit to leave trashy zswap entry on
the tree and lru list.

With this patch:
bpftrace -e 'kr:zswap_writeback_entry {@[(int32)retval]=count()}'
@[0]: 259744

Note: large folio can't have zswap entry for now, so don't bother
to add zswap entry invalidation in the large folio swap free path.

Link: https://lkml.kernel.org/r/20240201-b4-zswap-invalidate-entry-v2-2-99d4084260a0@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Chengming Zhou 2024-02-04 03:06:00 +00:00 committed by Andrew Morton
parent f9c0f1c32c
commit 0827a1fb14
4 changed files with 8 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/zswap.h
View File

@ -29,7 +29,7 @@ struct zswap_lruvec_state {
bool zswap_store(struct folio *folio);
bool zswap_load(struct folio *folio);
void zswap_invalidate(int type, pgoff_t offset);
void zswap_invalidate(swp_entry_t swp);
int zswap_swapon(int type, unsigned long nr_pages);
void zswap_swapoff(int type);
void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg);
@ -50,7 +50,7 @@ static inline bool zswap_load(struct folio *folio)
return false;
}
static inline void zswap_invalidate(int type, pgoff_t offset) {}
static inline void zswap_invalidate(swp_entry_t swp) {}
static inline int zswap_swapon(int type, unsigned long nr_pages)
{
return 0;

3
mm/swap_slots.c
View File

@ -273,6 +273,9 @@ void free_swap_slot(swp_entry_t entry)
{
struct swap_slots_cache *cache;
/* Large folio swap slot is not covered. */
zswap_invalidate(entry);
cache = raw_cpu_ptr(&swp_slots);
if (likely(use_swap_slot_cache && cache->slots_ret)) {
spin_lock_irq(&cache->free_lock);

1
mm/swapfile.c
View File

@ -744,7 +744,6 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
swap_slot_free_notify = NULL;
while (offset <= end) {
arch_swap_invalidate_page(si->type, offset);
zswap_invalidate(si->type, offset);
if (swap_slot_free_notify)
swap_slot_free_notify(si->bdev, offset);
offset++;

5
mm/zswap.c
View File

@ -1739,9 +1739,10 @@ bool zswap_load(struct folio *folio)
return true;
}
void zswap_invalidate(int type, pgoff_t offset)
void zswap_invalidate(swp_entry_t swp)
{
struct zswap_tree *tree = swap_zswap_tree(swp_entry(type, offset));
pgoff_t offset = swp_offset(swp);
struct zswap_tree *tree = swap_zswap_tree(swp);
struct zswap_entry *entry;
spin_lock(&tree->lock);