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Date: Thu, 8 Jun 2023 10:51:33 -0700
From: Nhat Pham <nphamcs@...il.com>
To: Domenico Cerasuolo <cerasuolodomenico@...il.com>
Cc: vitaly.wool@...sulko.com, minchan@...nel.org,
senozhatsky@...omium.org, yosryahmed@...gle.com,
linux-mm@...ck.org, ddstreet@...e.org, sjenning@...hat.com,
hannes@...xchg.org, akpm@...ux-foundation.org,
linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [RFC PATCH v2 5/7] mm: zswap: remove shrink from zpool interface
On Tue, Jun 6, 2023 at 7:56 AM Domenico Cerasuolo
<cerasuolodomenico@...il.com> wrote:
>
> 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.
>
> Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@...il.com>
> ---
> include/linux/zpool.h | 19 ++---------------
> mm/z3fold.c | 5 +----
> mm/zbud.c | 5 +----
> mm/zpool.c | 48 ++-----------------------------------------
> mm/zsmalloc.c | 5 +----
> mm/zswap.c | 27 +++++++-----------------
> 6 files changed, 14 insertions(+), 95 deletions(-)
>
> diff --git a/include/linux/zpool.h b/include/linux/zpool.h
> index e8997010612a..6b15a4213de5 100644
> --- a/include/linux/zpool.h
> +++ b/include/linux/zpool.h
> @@ -14,10 +14,6 @@
>
> 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.
> @@ -40,7 +36,7 @@ enum zpool_mapmode {
> 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);
> + gfp_t gfp);
>
> const char *zpool_get_type(struct zpool *pool);
>
> @@ -53,9 +49,6 @@ int zpool_malloc(struct zpool *pool, size_t size, gfp_t gfp,
>
> 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);
>
> @@ -72,7 +65,6 @@ u64 zpool_get_total_size(struct zpool *pool);
> * @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.
> @@ -87,10 +79,7 @@ struct zpool_driver {
> 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;
> @@ -98,9 +87,6 @@ struct zpool_driver {
> 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,
> enum zpool_mapmode mm);
> @@ -113,7 +99,6 @@ void zpool_register_driver(struct zpool_driver *driver);
>
> int zpool_unregister_driver(struct zpool_driver *driver);
>
> -bool zpool_evictable(struct zpool *pool);
> bool zpool_can_sleep_mapped(struct zpool *pool);
>
> #endif
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index 4af8741553ac..e84de91ecccb 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -1364,9 +1364,7 @@ static const struct movable_operations z3fold_mops = {
> * 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);
> }
> @@ -1409,7 +1407,6 @@ static struct zpool_driver z3fold_zpool_driver = {
> .destroy = z3fold_zpool_destroy,
> .malloc = z3fold_zpool_malloc,
> .free = z3fold_zpool_free,
> - .shrink = NULL,
> .map = z3fold_zpool_map,
> .unmap = z3fold_zpool_unmap,
> .total_size = z3fold_zpool_total_size,
> diff --git a/mm/zbud.c b/mm/zbud.c
> index 19bc662ef5e9..2190cc1f37b3 100644
> --- a/mm/zbud.c
> +++ b/mm/zbud.c
> @@ -380,9 +380,7 @@ static u64 zbud_get_pool_size(struct zbud_pool *pool)
> * 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);
> }
> @@ -425,7 +423,6 @@ static struct zpool_driver zbud_zpool_driver = {
> .destroy = zbud_zpool_destroy,
> .malloc = zbud_zpool_malloc,
> .free = zbud_zpool_free,
> - .shrink = NULL,
> .map = zbud_zpool_map,
> .unmap = zbud_zpool_unmap,
> .total_size = zbud_zpool_total_size,
> diff --git a/mm/zpool.c b/mm/zpool.c
> index 6a19c4a58f77..846410479c2f 100644
> --- a/mm/zpool.c
> +++ b/mm/zpool.c
> @@ -133,7 +133,6 @@ EXPORT_SYMBOL(zpool_has_pool);
> * @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
> @@ -145,8 +144,7 @@ EXPORT_SYMBOL(zpool_has_pool);
> *
> * 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;
> @@ -173,7 +171,7 @@ struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp,
> }
>
> 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);
> @@ -279,30 +277,6 @@ void zpool_free(struct zpool *zpool, unsigned long handle)
> zpool->driver->free(zpool->pool, handle);
> }
>
> -/**
> - * 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
> @@ -359,24 +333,6 @@ 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;
> -}
> -
> /**
> * zpool_can_sleep_mapped - Test if zpool can sleep when do mapped.
> * @zpool: The zpool to test
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 75386283dba0..634daa19b6c2 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -351,9 +351,7 @@ static void record_obj(unsigned long handle, unsigned long obj)
>
> #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
> @@ -420,7 +418,6 @@ static struct zpool_driver zs_zpool_driver = {
> .malloc_support_movable = true,
> .malloc = zs_zpool_malloc,
> .free = zs_zpool_free,
> - .shrink = NULL,
> .map = zs_zpool_map,
> .unmap = zs_zpool_unmap,
> .total_size = zs_zpool_total_size,
> diff --git a/mm/zswap.c b/mm/zswap.c
> index c99bafcefecf..2831bf56b168 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -254,10 +254,6 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
> 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 <
> @@ -375,12 +371,9 @@ static void zswap_free_entry(struct zswap_entry *entry)
> 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);
> }
> @@ -659,12 +652,8 @@ static void shrink_worker(struct work_struct *w)
> 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_shrink(pool);
> + ret = zswap_shrink(pool);
> if (ret) {
> zswap_reject_reclaim_fail++;
> if (ret != -EAGAIN)
> @@ -702,7 +691,7 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
> /* 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;
> @@ -1388,8 +1377,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
> 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);
> @@ -1495,8 +1483,7 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
> freeentry:
> spin_lock(&tree->lock);
> zswap_entry_put(tree, entry);
> - /* 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_move(&entry->lru, &entry->pool->lru);
> spin_unlock(&entry->pool->lru_lock);
> --
> 2.34.1
>
zsmalloc's shrink removal looks good to me.
Acked-by: Nhat Pham <nphamcs@...il.com>
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