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z3fold: add kref refcounting
With both coming and already present locking optimizations, introducing kref to reference-count z3fold objects is the right thing to do. Moreover, it makes buddied list no longer necessary, and allows for a simpler handling of headless pages. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/20170131214650.8ea78033d91ded233f552bc0@gmail.com Signed-off-by: Vitaly Wool <vitalywool@gmail.com> Reviewed-by: Dan Streetman <ddstreet@ieee.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vitaly Wool
Linus Torvalds
parent
2f1e5e4d84
commit
5a27aa8220
1 changed files with 71 additions and 88 deletions
145
mm/z3fold.c
145
mm/z3fold.c
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@ -52,6 +52,7 @@ enum buddy {
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* z3fold page, except for HEADLESS pages
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* @buddy: links the z3fold page into the relevant list in the pool
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* @page_lock: per-page lock
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* @refcount: reference cound for the z3fold page
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* @first_chunks: the size of the first buddy in chunks, 0 if free
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* @middle_chunks: the size of the middle buddy in chunks, 0 if free
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* @last_chunks: the size of the last buddy in chunks, 0 if free
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@ -60,6 +61,7 @@ enum buddy {
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struct z3fold_header {
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struct list_head buddy;
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spinlock_t page_lock;
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struct kref refcount;
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unsigned short first_chunks;
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unsigned short middle_chunks;
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unsigned short last_chunks;
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@ -95,8 +97,6 @@ struct z3fold_header {
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* @unbuddied: array of lists tracking z3fold pages that contain 2- buddies;
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* the lists each z3fold page is added to depends on the size of
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* its free region.
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* @buddied: list tracking the z3fold pages that contain 3 buddies;
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* these z3fold pages are full
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* @lru: list tracking the z3fold pages in LRU order by most recently
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* added buddy.
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* @pages_nr: number of z3fold pages in the pool.
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@ -109,7 +109,6 @@ struct z3fold_header {
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struct z3fold_pool {
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spinlock_t lock;
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struct list_head unbuddied[NCHUNKS];
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struct list_head buddied;
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struct list_head lru;
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atomic64_t pages_nr;
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const struct z3fold_ops *ops;
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@ -121,8 +120,7 @@ struct z3fold_pool {
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* Internal z3fold page flags
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*/
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enum z3fold_page_flags {
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UNDER_RECLAIM = 0,
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PAGE_HEADLESS,
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PAGE_HEADLESS = 0,
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MIDDLE_CHUNK_MAPPED,
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};
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@ -146,11 +144,11 @@ static struct z3fold_header *init_z3fold_page(struct page *page)
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struct z3fold_header *zhdr = page_address(page);
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INIT_LIST_HEAD(&page->lru);
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clear_bit(UNDER_RECLAIM, &page->private);
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clear_bit(PAGE_HEADLESS, &page->private);
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clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
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spin_lock_init(&zhdr->page_lock);
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kref_init(&zhdr->refcount);
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zhdr->first_chunks = 0;
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zhdr->middle_chunks = 0;
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zhdr->last_chunks = 0;
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@ -161,9 +159,24 @@ static struct z3fold_header *init_z3fold_page(struct page *page)
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}
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/* Resets the struct page fields and frees the page */
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static void free_z3fold_page(struct z3fold_header *zhdr)
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static void free_z3fold_page(struct page *page)
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{
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__free_page(virt_to_page(zhdr));
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__free_page(page);
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}
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static void release_z3fold_page(struct kref *ref)
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{
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struct z3fold_header *zhdr;
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struct page *page;
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zhdr = container_of(ref, struct z3fold_header, refcount);
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page = virt_to_page(zhdr);
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if (!list_empty(&zhdr->buddy))
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list_del(&zhdr->buddy);
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if (!list_empty(&page->lru))
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list_del(&page->lru);
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free_z3fold_page(page);
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}
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/* Lock a z3fold page */
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@ -178,7 +191,6 @@ static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
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spin_unlock(&zhdr->page_lock);
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}
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/*
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* Encodes the handle of a particular buddy within a z3fold page
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* Pool lock should be held as this function accesses first_num
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@ -257,7 +269,6 @@ static struct z3fold_pool *z3fold_create_pool(gfp_t gfp,
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spin_lock_init(&pool->lock);
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for_each_unbuddied_list(i, 0)
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INIT_LIST_HEAD(&pool->unbuddied[i]);
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INIT_LIST_HEAD(&pool->buddied);
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INIT_LIST_HEAD(&pool->lru);
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atomic64_set(&pool->pages_nr, 0);
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pool->ops = ops;
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@ -378,6 +389,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
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spin_unlock(&pool->lock);
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continue;
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}
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kref_get(&zhdr->refcount);
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list_del_init(&zhdr->buddy);
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spin_unlock(&pool->lock);
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@ -394,10 +406,12 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
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else if (zhdr->middle_chunks == 0)
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bud = MIDDLE;
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else {
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spin_lock(&pool->lock);
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list_add(&zhdr->buddy, &pool->buddied);
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spin_unlock(&pool->lock);
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z3fold_page_unlock(zhdr);
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spin_lock(&pool->lock);
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if (kref_put(&zhdr->refcount,
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release_z3fold_page))
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atomic64_dec(&pool->pages_nr);
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spin_unlock(&pool->lock);
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pr_err("No free chunks in unbuddied\n");
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WARN_ON(1);
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continue;
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@ -438,9 +452,6 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
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/* Add to unbuddied list */
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freechunks = num_free_chunks(zhdr);
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list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
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} else {
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/* Add to buddied list */
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list_add(&zhdr->buddy, &pool->buddied);
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}
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headless:
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@ -504,52 +515,29 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
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}
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}
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if (test_bit(UNDER_RECLAIM, &page->private)) {
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/* z3fold page is under reclaim, reclaim will free */
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if (bud != HEADLESS)
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z3fold_page_unlock(zhdr);
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return;
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}
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/* Remove from existing buddy list */
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if (bud != HEADLESS) {
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spin_lock(&pool->lock);
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/*
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* this object may have been removed from its list by
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* z3fold_alloc(). In that case we just do nothing,
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* z3fold_alloc() will allocate an object and add the page
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* to the relevant list.
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*/
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if (!list_empty(&zhdr->buddy)) {
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list_del(&zhdr->buddy);
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} else {
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spin_unlock(&pool->lock);
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z3fold_page_unlock(zhdr);
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return;
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}
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spin_unlock(&pool->lock);
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}
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if (bud == HEADLESS ||
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(zhdr->first_chunks == 0 && zhdr->middle_chunks == 0 &&
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zhdr->last_chunks == 0)) {
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/* z3fold page is empty, free */
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if (bud == HEADLESS) {
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spin_lock(&pool->lock);
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list_del(&page->lru);
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spin_unlock(&pool->lock);
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clear_bit(PAGE_HEADLESS, &page->private);
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if (bud != HEADLESS)
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z3fold_page_unlock(zhdr);
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free_z3fold_page(zhdr);
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free_z3fold_page(page);
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atomic64_dec(&pool->pages_nr);
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} else {
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if (zhdr->first_chunks != 0 || zhdr->middle_chunks != 0 ||
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zhdr->last_chunks != 0) {
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z3fold_compact_page(zhdr);
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/* Add to the unbuddied list */
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spin_lock(&pool->lock);
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if (!list_empty(&zhdr->buddy))
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list_del(&zhdr->buddy);
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freechunks = num_free_chunks(zhdr);
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list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
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spin_unlock(&pool->lock);
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}
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z3fold_page_unlock(zhdr);
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spin_lock(&pool->lock);
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if (kref_put(&zhdr->refcount, release_z3fold_page))
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atomic64_dec(&pool->pages_nr);
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spin_unlock(&pool->lock);
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}
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}
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@ -608,13 +596,13 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
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return -EINVAL;
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}
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page = list_last_entry(&pool->lru, struct page, lru);
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list_del(&page->lru);
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list_del_init(&page->lru);
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/* Protect z3fold page against free */
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set_bit(UNDER_RECLAIM, &page->private);
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zhdr = page_address(page);
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if (!test_bit(PAGE_HEADLESS, &page->private)) {
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list_del(&zhdr->buddy);
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if (!list_empty(&zhdr->buddy))
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list_del_init(&zhdr->buddy);
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kref_get(&zhdr->refcount);
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spin_unlock(&pool->lock);
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z3fold_page_lock(zhdr);
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/*
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@ -655,30 +643,19 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
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goto next;
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}
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next:
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if (!test_bit(PAGE_HEADLESS, &page->private))
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z3fold_page_lock(zhdr);
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clear_bit(UNDER_RECLAIM, &page->private);
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if ((test_bit(PAGE_HEADLESS, &page->private) && ret == 0) ||
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(zhdr->first_chunks == 0 && zhdr->last_chunks == 0 &&
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zhdr->middle_chunks == 0)) {
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/*
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* All buddies are now free, free the z3fold page and
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* return success.
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*/
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if (!test_and_clear_bit(PAGE_HEADLESS, &page->private))
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z3fold_page_unlock(zhdr);
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free_z3fold_page(zhdr);
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atomic64_dec(&pool->pages_nr);
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if (test_bit(PAGE_HEADLESS, &page->private)) {
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if (ret == 0) {
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free_z3fold_page(page);
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return 0;
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} else if (!test_bit(PAGE_HEADLESS, &page->private)) {
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if (zhdr->first_chunks != 0 &&
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zhdr->last_chunks != 0 &&
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zhdr->middle_chunks != 0) {
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/* Full, add to buddied list */
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spin_lock(&pool->lock);
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list_add(&zhdr->buddy, &pool->buddied);
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spin_unlock(&pool->lock);
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} else {
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spin_lock(&pool->lock);
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}
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} else {
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z3fold_page_lock(zhdr);
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if ((zhdr->first_chunks || zhdr->last_chunks ||
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zhdr->middle_chunks) &&
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!(zhdr->first_chunks && zhdr->last_chunks &&
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zhdr->middle_chunks)) {
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z3fold_compact_page(zhdr);
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/* add to unbuddied list */
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spin_lock(&pool->lock);
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@ -687,13 +664,19 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
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&pool->unbuddied[freechunks]);
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spin_unlock(&pool->lock);
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}
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z3fold_page_unlock(zhdr);
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spin_lock(&pool->lock);
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if (kref_put(&zhdr->refcount, release_z3fold_page)) {
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atomic64_dec(&pool->pages_nr);
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return 0;
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}
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}
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if (!test_bit(PAGE_HEADLESS, &page->private))
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z3fold_page_unlock(zhdr);
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spin_lock(&pool->lock);
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/* add to beginning of LRU */
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/*
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* Add to the beginning of LRU.
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* Pool lock has to be kept here to ensure the page has
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* not already been released
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*/
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list_add(&page->lru, &pool->lru);
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}
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spin_unlock(&pool->lock);
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