mm: zswap: remove page reclaim logic from zbud

 *		its free region.

 * @buddied:	list tracking the zbud pages that contain two buddies;

 *		these zbud pages are full

 * @lru:	list tracking the zbud pages in LRU order by most recently

 *		added buddy.

 * @pages_nr:	number of zbud pages in the pool.

 * @zpool:	zpool driver

 * @zpool_ops:	zpool operations structure with an evict callback

 *

 * This structure is allocated at pool creation time and maintains metadata

 * pertaining to a particular zbud pool.

		struct list_head buddied;

		struct list_head unbuddied[NCHUNKS];

	};

	struct list_head lru;

	u64 pages_nr;

	struct zpool *zpool;

	const struct zpool_ops *zpool_ops;

};

/*

 * struct zbud_header - zbud page metadata occupying the first chunk of each

 *			zbud page.

 * @buddy:	links the zbud page into the unbuddied/buddied lists in the pool

 * @lru:	links the zbud page into the lru list in the pool

 * @first_chunks:	the size of the first buddy in chunks, 0 if free

 * @last_chunks:	the size of the last buddy in chunks, 0 if free

 */

struct zbud_header {

	struct list_head buddy;

	struct list_head lru;

	unsigned int first_chunks;

	unsigned int last_chunks;

	bool under_reclaim;

};

/*****************

	zhdr->first_chunks = 0;

	zhdr->last_chunks = 0;

	INIT_LIST_HEAD(&zhdr->buddy);

	INIT_LIST_HEAD(&zhdr->lru);

	zhdr->under_reclaim = false;

	return zhdr;

}

	for_each_unbuddied_list(i, 0)

		INIT_LIST_HEAD(&pool->unbuddied[i]);

	INIT_LIST_HEAD(&pool->buddied);

	INIT_LIST_HEAD(&pool->lru);

	pool->pages_nr = 0;

	return pool;

}

		list_add(&zhdr->buddy, &pool->buddied);

	}

	/* Add/move zbud page to beginning of LRU */

	if (!list_empty(&zhdr->lru))

		list_del(&zhdr->lru);

	list_add(&zhdr->lru, &pool->lru);

	*handle = encode_handle(zhdr, bud);

	spin_unlock(&pool->lock);

 * zbud_free() - frees the allocation associated with the given handle

 * @pool:	pool in which the allocation resided

 * @handle:	handle associated with the allocation returned by zbud_alloc()

 *

 * In the case that the zbud page in which the allocation resides is under

 * reclaim, as indicated by the PG_reclaim flag being set, this function

 * only sets the first|last_chunks to 0.  The page is actually freed

 * once both buddies are evicted (see zbud_reclaim_page() below).

 */

static void zbud_free(struct zbud_pool *pool, unsigned long handle)

{

	else

		zhdr->first_chunks = 0;

	if (zhdr->under_reclaim) {

		/* zbud page is under reclaim, reclaim will free */

		spin_unlock(&pool->lock);

		return;

	}

	/* Remove from existing buddy list */

	list_del(&zhdr->buddy);

	if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {

		/* zbud page is empty, free */

		list_del(&zhdr->lru);

		free_zbud_page(zhdr);

		pool->pages_nr--;

	} else {

	spin_unlock(&pool->lock);

}

/**

 * zbud_reclaim_page() - evicts allocations from a pool page and frees it

 * @pool:	pool from which a page will attempt to be evicted

 * @retries:	number of pages on the LRU list for which eviction will

 *		be attempted before failing

 *

 * zbud reclaim is different from normal system reclaim in that the reclaim is

 * done from the bottom, up.  This is because only the bottom layer, zbud, has

 * information on how the allocations are organized within each zbud page. This

 * has the potential to create interesting locking situations between zbud and

 * the user, however.

 *

 * To avoid these, this is how zbud_reclaim_page() should be called:

 *

 * The user detects a page should be reclaimed and calls zbud_reclaim_page().

 * zbud_reclaim_page() will remove a zbud page from the pool LRU list and call

 * the user-defined eviction handler with the pool and handle as arguments.

 *

 * If the handle can not be evicted, the eviction handler should return

 * non-zero. zbud_reclaim_page() will add the zbud page back to the

 * appropriate list and try the next zbud page on the LRU up to

 * a user defined number of retries.

 *

 * If the handle is successfully evicted, the eviction handler should

 * return 0 _and_ should have called zbud_free() on the handle. zbud_free()

 * contains logic to delay freeing the page if the page is under reclaim,

 * as indicated by the setting of the PG_reclaim flag on the underlying page.

 *

 * If all buddies in the zbud page are successfully evicted, then the

 * zbud page can be freed.

 *

 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are

 * no pages to evict or an eviction handler is not registered, -EAGAIN if

 * the retry limit was hit.

 */

static int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries)

{

	int i, ret, freechunks;

	struct zbud_header *zhdr;

	unsigned long first_handle = 0, last_handle = 0;

	spin_lock(&pool->lock);

	if (list_empty(&pool->lru)) {

		spin_unlock(&pool->lock);

		return -EINVAL;

	}

	for (i = 0; i < retries; i++) {

		zhdr = list_last_entry(&pool->lru, struct zbud_header, lru);

		list_del(&zhdr->lru);

		list_del(&zhdr->buddy);

		/* Protect zbud page against free */

		zhdr->under_reclaim = true;

		/*

		 * We need encode the handles before unlocking, since we can

		 * race with free that will set (first|last)_chunks to 0

		 */

		first_handle = 0;

		last_handle = 0;

		if (zhdr->first_chunks)

			first_handle = encode_handle(zhdr, FIRST);

		if (zhdr->last_chunks)

			last_handle = encode_handle(zhdr, LAST);

		spin_unlock(&pool->lock);

		/* Issue the eviction callback(s) */

		if (first_handle) {

			ret = pool->zpool_ops->evict(pool->zpool, first_handle);

			if (ret)

				goto next;

		}

		if (last_handle) {

			ret = pool->zpool_ops->evict(pool->zpool, last_handle);

			if (ret)

				goto next;

		}

next:

		spin_lock(&pool->lock);

		zhdr->under_reclaim = false;

		if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {

			/*

			 * Both buddies are now free, free the zbud page and

			 * return success.

			 */

			free_zbud_page(zhdr);

			pool->pages_nr--;

			spin_unlock(&pool->lock);

			return 0;

		} else if (zhdr->first_chunks == 0 ||

				zhdr->last_chunks == 0) {

			/* add to unbuddied list */

			freechunks = num_free_chunks(zhdr);

			list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);

		} else {

			/* add to buddied list */

			list_add(&zhdr->buddy, &pool->buddied);

		}

		/* add to beginning of LRU */

		list_add(&zhdr->lru, &pool->lru);

	}

	spin_unlock(&pool->lock);

	return -EAGAIN;

}

/**

 * zbud_map() - maps the allocation associated with the given handle

 * @pool:	pool in which the allocation resides

			       const struct zpool_ops *zpool_ops,

			       struct zpool *zpool)

{

	struct zbud_pool *pool;

	pool = zbud_create_pool(gfp);

	if (pool) {

		pool->zpool = zpool;

		pool->zpool_ops = zpool_ops;

	}

	return pool;

	return zbud_create_pool(gfp);

}

static void zbud_zpool_destroy(void *pool)

	zbud_free(pool, handle);

}

static int zbud_zpool_shrink(void *pool, unsigned int pages,

			unsigned int *reclaimed)

{

	unsigned int total = 0;

	int ret = -EINVAL;

	while (total < pages) {

		ret = zbud_reclaim_page(pool, 8);

		if (ret < 0)

			break;

		total++;

	}

	if (reclaimed)

		*reclaimed = total;

	return ret;

}

static void *zbud_zpool_map(void *pool, unsigned long handle,

			enum zpool_mapmode mm)

{

	.destroy =	zbud_zpool_destroy,

	.malloc =	zbud_zpool_malloc,

	.free =		zbud_zpool_free,

	.shrink =	zbud_zpool_shrink,

	.map =		zbud_zpool_map,

	.unmap =	zbud_zpool_unmap,

	.total_size =	zbud_zpool_total_size,