Commit ff9d5ba2 authored by Domenico Cerasuolo's avatar Domenico Cerasuolo Committed by Andrew Morton
Browse files

mm: zswap: simplify writeback function 

zswap_writeback_entry() used to be a callback for the backends, which
don't know about struct zswap_entry.

Now that the only user is the generic zswap LRU reclaimer, it can be
simplified: pass the pinned zswap_entry directly, and consolidate the
refcount management in the shrink function.

Link: https://lkml.kernel.org/r/20230612093815.133504-7-cerasuolodomenico@gmail.com


Signed-off-by: default avatarDomenico Cerasuolo <cerasuolodomenico@gmail.com>
Tested-by: default avatarYosry Ahmed <yosryahmed@google.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 35499e2b

mm/zswap.c

+19 −51
Original line number Diff line number Diff line
@@ -254,7 +254,8 @@ static bool zswap_has_pool; 
	pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,		\

		 zpool_get_type((p)->zpool))



static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);

static int zswap_writeback_entry(struct zswap_entry *entry, struct zswap_header *zhdr,

				 struct zswap_tree *tree);

static int zswap_pool_get(struct zswap_pool *pool);

static void zswap_pool_put(struct zswap_pool *pool);
@@ -635,7 +636,7 @@ static int zswap_reclaim_entry(struct zswap_pool *pool) 
	zswap_entry_get(entry);

	spin_unlock(&tree->lock);



	ret = zswap_writeback_entry(pool->zpool, entry->handle);

	ret = zswap_writeback_entry(entry, zhdr, tree);



	spin_lock(&tree->lock);

	if (ret) {
@@ -643,8 +644,17 @@ static int zswap_reclaim_entry(struct zswap_pool *pool) 
		spin_lock(&pool->lru_lock);

		list_move(&entry->lru, &pool->lru);

		spin_unlock(&pool->lru_lock);

		goto put_unlock;

	}



	/* Check for invalidate() race */

	if (entry != zswap_rb_search(&tree->rbroot, swpoffset))

		goto put_unlock;



	/* Drop base reference */

	zswap_entry_put(tree, entry);



put_unlock:

	/* Drop local reference */

	zswap_entry_put(tree, entry);

unlock:
@@ -1045,16 +1055,14 @@ static int zswap_get_swap_cache_page(swp_entry_t entry, 
 * the swap cache, the compressed version stored by zswap can be

 * freed.

 */

static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)

static int zswap_writeback_entry(struct zswap_entry *entry, struct zswap_header *zhdr,

				 struct zswap_tree *tree)

{

	struct zswap_header *zhdr;

	swp_entry_t swpentry;

	struct zswap_tree *tree;

	pgoff_t offset;

	struct zswap_entry *entry;

	swp_entry_t swpentry = zhdr->swpentry;

	struct page *page;

	struct scatterlist input, output;

	struct crypto_acomp_ctx *acomp_ctx;

	struct zpool *pool = entry->pool->zpool;



	u8 *src, *tmp = NULL;

	unsigned int dlen;
@@ -1069,25 +1077,6 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) 
			return -ENOMEM;

	}



	/* extract swpentry from data */

	zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);

	swpentry = zhdr->swpentry; /* here */

	tree = zswap_trees[swp_type(swpentry)];

	offset = swp_offset(swpentry);

	zpool_unmap_handle(pool, handle);



	/* find and ref zswap entry */

	spin_lock(&tree->lock);

	entry = zswap_entry_find_get(&tree->rbroot, offset);

	if (!entry) {

		/* entry was invalidated */

		spin_unlock(&tree->lock);

		kfree(tmp);

		return 0;

	}

	spin_unlock(&tree->lock);

	BUG_ON(offset != entry->offset);



	/* try to allocate swap cache page */

	switch (zswap_get_swap_cache_page(swpentry, &page)) {

	case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
@@ -1121,12 +1110,12 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) 
		acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);

		dlen = PAGE_SIZE;



		zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);

		zhdr = zpool_map_handle(pool, entry->handle, ZPOOL_MM_RO);

		src = (u8 *)zhdr + sizeof(struct zswap_header);

		if (!zpool_can_sleep_mapped(pool)) {

			memcpy(tmp, src, entry->length);

			src = tmp;

			zpool_unmap_handle(pool, handle);

			zpool_unmap_handle(pool, entry->handle);

		}



		mutex_lock(acomp_ctx->mutex);
@@ -1141,7 +1130,7 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) 
		if (!zpool_can_sleep_mapped(pool))

			kfree(tmp);

		else

			zpool_unmap_handle(pool, handle);

			zpool_unmap_handle(pool, entry->handle);



		BUG_ON(ret);

		BUG_ON(dlen != PAGE_SIZE);
@@ -1158,23 +1147,7 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) 
	put_page(page);

	zswap_written_back_pages++;



	spin_lock(&tree->lock);

	/* drop local reference */

	zswap_entry_put(tree, entry);



	/*

	* There are two possible situations for entry here:

	* (1) refcount is 1(normal case),  entry is valid and on the tree

	* (2) refcount is 0, entry is freed and not on the tree

	*     because invalidate happened during writeback

	*  search the tree and free the entry if find entry

	*/

	if (entry == zswap_rb_search(&tree->rbroot, offset))

		zswap_entry_put(tree, entry);

	spin_unlock(&tree->lock);



	return ret;



fail:

	if (!zpool_can_sleep_mapped(pool))

		kfree(tmp);
@@ -1183,13 +1156,8 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) 
	* if we get here due to ZSWAP_SWAPCACHE_EXIST

	* a load may be happening concurrently.

	* it is safe and okay to not free the entry.

	* if we free the entry in the following put

	* it is also okay to return !0

	*/

	spin_lock(&tree->lock);

	zswap_entry_put(tree, entry);

	spin_unlock(&tree->lock);



	return ret;

}