mm: zswap: remove shrink from zpool interface

Now that all three zswap backends have removed their shrink code, it is
no longer necessary for the zpool interface to include shrink/writeback
endpoints.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Domenico Cerasuolo <[e-mail]>
Reviewed-by: Yosry Ahmed <[e-mail]>
Acked-by: Nhat Pham <[e-mail]>
Acked-by: Johannes Weiner <[e-mail]>
Reviewed-by: Sergey Senozhatsky <[e-mail]>
Cc: Dan Streetman <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Cc: Seth Jennings <[e-mail]>
Cc: Vitaly Wool <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/linux/zpool.h

···
 
 struct zpool;
 
-struct zpool_ops {
-	int (*evict)(struct zpool *pool, unsigned long handle);
-};
-
 /*
  * Control how a handle is mapped.  It will be ignored if the
  * implementation does not support it.  Its use is optional.
···
 
 bool zpool_has_pool(char *type);
 
-struct zpool *zpool_create_pool(const char *type, const char *name,
-			gfp_t gfp, const struct zpool_ops *ops);
+struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp);
 
 const char *zpool_get_type(struct zpool *pool);
 
···
 			unsigned long *handle);
 
 void zpool_free(struct zpool *pool, unsigned long handle);
-
-int zpool_shrink(struct zpool *pool, unsigned int pages,
-			unsigned int *reclaimed);
 
 void *zpool_map_handle(struct zpool *pool, unsigned long handle,
 			enum zpool_mapmode mm);
···
  * @destroy:	destroy a pool.
  * @malloc:	allocate mem from a pool.
  * @free:	free mem from a pool.
- * @shrink:	shrink the pool.
  * @sleep_mapped: whether zpool driver can sleep during map.
  * @map:	map a handle.
  * @unmap:	unmap a handle.
···
 	atomic_t refcount;
 	struct list_head list;
 
-	void *(*create)(const char *name,
-			gfp_t gfp,
-			const struct zpool_ops *ops,
-			struct zpool *zpool);
+	void *(*create)(const char *name, gfp_t gfp);
 	void (*destroy)(void *pool);
 
 	bool malloc_support_movable;
 	int (*malloc)(void *pool, size_t size, gfp_t gfp,
 				unsigned long *handle);
 	void (*free)(void *pool, unsigned long handle);
-
-	int (*shrink)(void *pool, unsigned int pages,
-				unsigned int *reclaimed);
 
 	bool sleep_mapped;
 	void *(*map)(void *pool, unsigned long handle,
···
 
 int zpool_unregister_driver(struct zpool_driver *driver);
 
-bool zpool_evictable(struct zpool *pool);
 bool zpool_can_sleep_mapped(struct zpool *pool);
 
 #endif

mm/z3fold.c

···
  * zpool
  ****************/
 
-static void *z3fold_zpool_create(const char *name, gfp_t gfp,
-			       const struct zpool_ops *zpool_ops,
-			       struct zpool *zpool)
+static void *z3fold_zpool_create(const char *name, gfp_t gfp)
 {
 	return z3fold_create_pool(name, gfp);
 }

mm/zbud.c

···
  * zpool
  ****************/
 
-static void *zbud_zpool_create(const char *name, gfp_t gfp,
-			       const struct zpool_ops *zpool_ops,
-			       struct zpool *zpool)
+static void *zbud_zpool_create(const char *name, gfp_t gfp)
 {
 	return zbud_create_pool(gfp);
 }

mm/zpool.c

···
  * @type:	The type of the zpool to create (e.g. zbud, zsmalloc)
  * @name:	The name of the zpool (e.g. zram0, zswap)
  * @gfp:	The GFP flags to use when allocating the pool.
- * @ops:	The optional ops callback.
  *
  * This creates a new zpool of the specified type.  The gfp flags will be
  * used when allocating memory, if the implementation supports it.  If the
···
  *
  * Returns: New zpool on success, NULL on failure.
  */
-struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp,
-		const struct zpool_ops *ops)
+struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp)
 {
 	struct zpool_driver *driver;
 	struct zpool *zpool;
···
 	}
 
 	zpool->driver = driver;
-	zpool->pool = driver->create(name, gfp, ops, zpool);
+	zpool->pool = driver->create(name, gfp);
 
 	if (!zpool->pool) {
 		pr_err("couldn't create %s pool\n", type);
···
 }
 
 /**
- * zpool_shrink() - Shrink the pool size
- * @zpool:	The zpool to shrink.
- * @pages:	The number of pages to shrink the pool.
- * @reclaimed:	The number of pages successfully evicted.
- *
- * This attempts to shrink the actual memory size of the pool
- * by evicting currently used handle(s).  If the pool was
- * created with no zpool_ops, or the evict call fails for any
- * of the handles, this will fail.  If non-NULL, the @reclaimed
- * parameter will be set to the number of pages reclaimed,
- * which may be more than the number of pages requested.
- *
- * Implementations must guarantee this to be thread-safe.
- *
- * Returns: 0 on success, negative value on error/failure.
- */
-int zpool_shrink(struct zpool *zpool, unsigned int pages,
-			unsigned int *reclaimed)
-{
-	return zpool->driver->shrink ?
-	       zpool->driver->shrink(zpool->pool, pages, reclaimed) : -EINVAL;
-}
-
-/**
  * zpool_map_handle() - Map a previously allocated handle into memory
  * @zpool:	The zpool that the handle was allocated from
  * @handle:	The handle to map
···
 u64 zpool_get_total_size(struct zpool *zpool)
 {
 	return zpool->driver->total_size(zpool->pool);
-}
-
-/**
- * zpool_evictable() - Test if zpool is potentially evictable
- * @zpool:	The zpool to test
- *
- * Zpool is only potentially evictable when it's created with struct
- * zpool_ops.evict and its driver implements struct zpool_driver.shrink.
- *
- * However, it doesn't necessarily mean driver will use zpool_ops.evict
- * in its implementation of zpool_driver.shrink. It could do internal
- * defragmentation instead.
- *
- * Returns: true if potentially evictable; false otherwise.
- */
-bool zpool_evictable(struct zpool *zpool)
-{
-	return zpool->driver->shrink;
 }
 
 /**

mm/zsmalloc.c

···
 
 #ifdef CONFIG_ZPOOL
 
-static void *zs_zpool_create(const char *name, gfp_t gfp,
-			     const struct zpool_ops *zpool_ops,
-			     struct zpool *zpool)
+static void *zs_zpool_create(const char *name, gfp_t gfp)
 {
 	/*
 	 * Ignore global gfp flags: zs_malloc() may be invoked from

mm/zswap.c

···
 static int zswap_pool_get(struct zswap_pool *pool);
 static void zswap_pool_put(struct zswap_pool *pool);
 
-static const struct zpool_ops zswap_zpool_ops = {
-	.evict = zswap_writeback_entry
-};
-
 static bool zswap_is_full(void)
 {
 	return totalram_pages() * zswap_max_pool_percent / 100 <
···
 	if (!entry->length)
 		atomic_dec(&zswap_same_filled_pages);
 	else {
-		/* zpool_evictable will be removed once all 3 backends have migrated */
-		if (!zpool_evictable(entry->pool->zpool)) {
-			spin_lock(&entry->pool->lru_lock);
-			list_del(&entry->lru);
-			spin_unlock(&entry->pool->lru_lock);
-		}
+		spin_lock(&entry->pool->lru_lock);
+		list_del(&entry->lru);
+		spin_unlock(&entry->pool->lru_lock);
 		zpool_free(entry->pool->zpool, entry->handle);
 		zswap_pool_put(entry->pool);
 	}
···
 						shrink_work);
 	int ret, failures = 0;
 
-	/* zpool_evictable will be removed once all 3 backends have migrated */
 	do {
-		if (zpool_evictable(pool->zpool))
-			ret = zpool_shrink(pool->zpool, 1, NULL);
-		else
-			ret = zswap_reclaim_entry(pool);
+		ret = zswap_reclaim_entry(pool);
 		if (ret) {
 			zswap_reject_reclaim_fail++;
 			if (ret != -EAGAIN)
···
 	/* unique name for each pool specifically required by zsmalloc */
 	snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
 
-	pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
+	pool->zpool = zpool_create_pool(type, name, gfp);
 	if (!pool->zpool) {
 		pr_err("%s zpool not available\n", type);
 		goto error;
···
 			zswap_entry_put(tree, dupentry);
 		}
 	} while (ret == -EEXIST);
-	/* zpool_evictable will be removed once all 3 backends have migrated */
-	if (entry->length && !zpool_evictable(entry->pool->zpool)) {
+	if (entry->length) {
 		spin_lock(&entry->pool->lru_lock);
 		list_add(&entry->lru, &entry->pool->lru);
 		spin_unlock(&entry->pool->lru_lock);
···
 	if (!ret && zswap_exclusive_loads_enabled) {
 		zswap_invalidate_entry(tree, entry);
 		*exclusive = true;
-	} else if (entry->length && !zpool_evictable(entry->pool->zpool)) {
-		/* zpool_evictable will be removed once all 3 backends have migrated */
+	} else if (entry->length) {
 		spin_lock(&entry->pool->lru_lock);
 		list_move(&entry->lru, &entry->pool->lru);
 		spin_unlock(&entry->pool->lru_lock);