[PATCH v7 2/6] zpool: clean out dead code

From: Nhat Pham
Date: Mon Nov 28 2022 - 14:16:28 EST

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In reply to: Sergey Senozhatsky: "Re: [PATCH v7 1/6] zswap: fix writeback lock ordering for zsmalloc"
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From: Johannes Weiner <hannes@xxxxxxxxxxx>

There is a lot of provision for flexibility that isn't actually needed
or used. Zswap (the only zpool user) always passes zpool_ops with an
.evict method set. The backends who reclaim only do so for zswap, so
they can also directly call zpool_ops without indirection or checks.

Finally, there is no need to check the retries parameters and bail
with -EINVAL in the reclaim function, when that's called just a few
lines below with a hard-coded 8. There is no need to duplicate the
evictable and sleep_mapped attrs from the driver in zpool_ops.

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx>
Reviewed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
---
mm/z3fold.c | 36 +++++-------------------------------
mm/zbud.c | 32 +++++---------------------------
mm/zpool.c | 10 ++--------
3 files changed, 12 insertions(+), 66 deletions(-)

diff --git a/mm/z3fold.c b/mm/z3fold.c
index cf71da10d04e..a4de0c317ac7 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -68,9 +68,6 @@
* Structures
*****************/
struct z3fold_pool;
-struct z3fold_ops {
- int (*evict)(struct z3fold_pool *pool, unsigned long handle);
-};

enum buddy {
HEADLESS = 0,
@@ -138,8 +135,6 @@ struct z3fold_header {
* @stale: list of pages marked for freeing
* @pages_nr: number of z3fold pages in the pool.
* @c_handle: cache for z3fold_buddy_slots allocation
- * @ops: pointer to a structure of user defined operations specified at
- * pool creation time.
* @zpool: zpool driver
* @zpool_ops: zpool operations structure with an evict callback
* @compact_wq: workqueue for page layout background optimization
@@ -158,7 +153,6 @@ struct z3fold_pool {
struct list_head stale;
atomic64_t pages_nr;
struct kmem_cache *c_handle;
- const struct z3fold_ops *ops;
struct zpool *zpool;
const struct zpool_ops *zpool_ops;
struct workqueue_struct *compact_wq;
@@ -907,13 +901,11 @@ static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
* z3fold_create_pool() - create a new z3fold pool
* @name: pool name
* @gfp: gfp flags when allocating the z3fold pool structure
- * @ops: user-defined operations for the z3fold pool
*
* Return: pointer to the new z3fold pool or NULL if the metadata allocation
* failed.
*/
-static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
- const struct z3fold_ops *ops)
+static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp)
{
struct z3fold_pool *pool = NULL;
int i, cpu;
@@ -949,7 +941,6 @@ static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
if (!pool->release_wq)
goto out_wq;
INIT_WORK(&pool->work, free_pages_work);
- pool->ops = ops;
return pool;

out_wq:
@@ -1230,10 +1221,6 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
slots.pool = (unsigned long)pool | (1 << HANDLES_NOFREE);

spin_lock(&pool->lock);
- if (!pool->ops || !pool->ops->evict || retries == 0) {
- spin_unlock(&pool->lock);
- return -EINVAL;
- }
for (i = 0; i < retries; i++) {
if (list_empty(&pool->lru)) {
spin_unlock(&pool->lock);
@@ -1319,17 +1306,17 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
}
/* Issue the eviction callback(s) */
if (middle_handle) {
- ret = pool->ops->evict(pool, middle_handle);
+ ret = pool->zpool_ops->evict(pool->zpool, middle_handle);
if (ret)
goto next;
}
if (first_handle) {
- ret = pool->ops->evict(pool, first_handle);
+ ret = pool->zpool_ops->evict(pool->zpool, first_handle);
if (ret)
goto next;
}
if (last_handle) {
- ret = pool->ops->evict(pool, last_handle);
+ ret = pool->zpool_ops->evict(pool->zpool, last_handle);
if (ret)
goto next;
}
@@ -1593,26 +1580,13 @@ static const struct movable_operations z3fold_mops = {
* zpool
****************/

-static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
-{
- if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
- return pool->zpool_ops->evict(pool->zpool, handle);
- else
- return -ENOENT;
-}
-
-static const struct z3fold_ops z3fold_zpool_ops = {
- .evict = z3fold_zpool_evict
-};
-
static void *z3fold_zpool_create(const char *name, gfp_t gfp,
const struct zpool_ops *zpool_ops,
struct zpool *zpool)
{
struct z3fold_pool *pool;

- pool = z3fold_create_pool(name, gfp,
- zpool_ops ? &z3fold_zpool_ops : NULL);
+ pool = z3fold_create_pool(name, gfp);
if (pool) {
pool->zpool = zpool;
pool->zpool_ops = zpool_ops;
diff --git a/mm/zbud.c b/mm/zbud.c
index 6348932430b8..3acd26193920 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -74,10 +74,6 @@

struct zbud_pool;

-struct zbud_ops {
- int (*evict)(struct zbud_pool *pool, unsigned long handle);
-};
-
/**
* struct zbud_pool - stores metadata for each zbud pool
* @lock: protects all pool fields and first|last_chunk fields of any
@@ -90,8 +86,6 @@ struct zbud_ops {
* @lru: list tracking the zbud pages in LRU order by most recently
* added buddy.
* @pages_nr: number of zbud pages in the pool.
- * @ops: pointer to a structure of user defined operations specified at
- * pool creation time.
* @zpool: zpool driver
* @zpool_ops: zpool operations structure with an evict callback
*
@@ -110,7 +104,6 @@ struct zbud_pool {
};
struct list_head lru;
u64 pages_nr;
- const struct zbud_ops *ops;
struct zpool *zpool;
const struct zpool_ops *zpool_ops;
};
@@ -212,12 +205,11 @@ static int num_free_chunks(struct zbud_header *zhdr)
/**
* zbud_create_pool() - create a new zbud pool
* @gfp: gfp flags when allocating the zbud pool structure
- * @ops: user-defined operations for the zbud pool
*
* Return: pointer to the new zbud pool or NULL if the metadata allocation
* failed.
*/
-static struct zbud_pool *zbud_create_pool(gfp_t gfp, const struct zbud_ops *ops)
+static struct zbud_pool *zbud_create_pool(gfp_t gfp)
{
struct zbud_pool *pool;
int i;
@@ -231,7 +223,6 @@ static struct zbud_pool *zbud_create_pool(gfp_t gfp, const struct zbud_ops *ops)
INIT_LIST_HEAD(&pool->buddied);
INIT_LIST_HEAD(&pool->lru);
pool->pages_nr = 0;
- pool->ops = ops;
return pool;
}

@@ -419,8 +410,7 @@ static int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries)
unsigned long first_handle = 0, last_handle = 0;

spin_lock(&pool->lock);
- if (!pool->ops || !pool->ops->evict || list_empty(&pool->lru) ||
- retries == 0) {
+ if (list_empty(&pool->lru)) {
spin_unlock(&pool->lock);
return -EINVAL;
}
@@ -444,12 +434,12 @@ static int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries)

/* Issue the eviction callback(s) */
if (first_handle) {
- ret = pool->ops->evict(pool, first_handle);
+ ret = pool->zpool_ops->evict(pool->zpool, first_handle);
if (ret)
goto next;
}
if (last_handle) {
- ret = pool->ops->evict(pool, last_handle);
+ ret = pool->zpool_ops->evict(pool->zpool, last_handle);
if (ret)
goto next;
}
@@ -524,25 +514,13 @@ static u64 zbud_get_pool_size(struct zbud_pool *pool)
* zpool
****************/

-static int zbud_zpool_evict(struct zbud_pool *pool, unsigned long handle)
-{
- if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
- return pool->zpool_ops->evict(pool->zpool, handle);
- else
- return -ENOENT;
-}
-
-static const struct zbud_ops zbud_zpool_ops = {
- .evict = zbud_zpool_evict
-};
-
static void *zbud_zpool_create(const char *name, gfp_t gfp,
const struct zpool_ops *zpool_ops,
struct zpool *zpool)
{
struct zbud_pool *pool;

- pool = zbud_create_pool(gfp, zpool_ops ? &zbud_zpool_ops : NULL);
+ pool = zbud_create_pool(gfp);
if (pool) {
pool->zpool = zpool;
pool->zpool_ops = zpool_ops;
diff --git a/mm/zpool.c b/mm/zpool.c
index f46c0d5e766c..571f5c5031dd 100644
--- a/mm/zpool.c
+++ b/mm/zpool.c
@@ -21,9 +21,6 @@
struct zpool {
struct zpool_driver *driver;
void *pool;
- const struct zpool_ops *ops;
- bool evictable;
- bool can_sleep_mapped;
};

static LIST_HEAD(drivers_head);
@@ -177,9 +174,6 @@ 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->ops = ops;
- zpool->evictable = driver->shrink && ops && ops->evict;
- zpool->can_sleep_mapped = driver->sleep_mapped;

if (!zpool->pool) {
pr_err("couldn't create %s pool\n", type);
@@ -380,7 +374,7 @@ u64 zpool_get_total_size(struct zpool *zpool)
*/
bool zpool_evictable(struct zpool *zpool)
{
- return zpool->evictable;
+ return zpool->driver->shrink;
}

/**
@@ -398,7 +392,7 @@ bool zpool_evictable(struct zpool *zpool)
*/
bool zpool_can_sleep_mapped(struct zpool *zpool)
{
- return zpool->can_sleep_mapped;
+ return zpool->driver->sleep_mapped;
}

MODULE_LICENSE("GPL");
--
2.30.2

Next message: Nhat Pham: "[PATCH v7 3/6] zsmalloc: Consolidate zs_pool's migrate_lock and size_class's locks"
Previous message: Nhat Pham: "[PATCH v7 1/6] zswap: fix writeback lock ordering for zsmalloc"
In reply to: Sergey Senozhatsky: "Re: [PATCH v7 1/6] zswap: fix writeback lock ordering for zsmalloc"
Next in thread: Nhat Pham: "[PATCH v7 3/6] zsmalloc: Consolidate zs_pool's migrate_lock and size_class's locks"
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