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![Vitaly Wool](/assets/img/avatar_default.png)
Stress testing of the current z3fold implementation on a 8-core system
revealed it was possible that a z3fold page deleted from its unbuddied
list in z3fold_alloc() would be put on another unbuddied list by
z3fold_free() while z3fold_alloc() is still processing it. This has
been introduced with commit 5a27aa822
("z3fold: add kref refcounting")
due to the removal of special handling of a z3fold page not on any list
in z3fold_free().
To fix this, the z3fold page lock should be taken in z3fold_alloc()
before the pool lock is released. To avoid deadlocking, we just try to
lock the page as soon as we get a hold of it, and if trylock fails, we
drop this page and take the next one.
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: <Oleksiy.Avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
889 lines
24 KiB
C
889 lines
24 KiB
C
/*
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* z3fold.c
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*
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* Author: Vitaly Wool <vitaly.wool@konsulko.com>
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* Copyright (C) 2016, Sony Mobile Communications Inc.
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*
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* This implementation is based on zbud written by Seth Jennings.
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*
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* z3fold is an special purpose allocator for storing compressed pages. It
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* can store up to three compressed pages per page which improves the
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* compression ratio of zbud while retaining its main concepts (e. g. always
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* storing an integral number of objects per page) and simplicity.
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* It still has simple and deterministic reclaim properties that make it
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* preferable to a higher density approach (with no requirement on integral
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* number of object per page) when reclaim is used.
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*
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* As in zbud, pages are divided into "chunks". The size of the chunks is
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* fixed at compile time and is determined by NCHUNKS_ORDER below.
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*
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* z3fold doesn't export any API and is meant to be used via zpool API.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/atomic.h>
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#include <linux/list.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/preempt.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/zpool.h>
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/*****************
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* Structures
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*****************/
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struct z3fold_pool;
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struct z3fold_ops {
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int (*evict)(struct z3fold_pool *pool, unsigned long handle);
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};
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enum buddy {
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HEADLESS = 0,
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FIRST,
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MIDDLE,
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LAST,
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BUDDIES_MAX
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};
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/*
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* struct z3fold_header - z3fold page metadata occupying the first chunk of each
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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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* @first_num: the starting number (for the first handle)
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*/
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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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unsigned short start_middle;
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unsigned short first_num:2;
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};
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/*
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* NCHUNKS_ORDER determines the internal allocation granularity, effectively
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* adjusting internal fragmentation. It also determines the number of
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* freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
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* allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
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* in the beginning of an allocated page are occupied by z3fold header, so
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* NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
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* which shows the max number of free chunks in z3fold page, also there will
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* be 63, or 62, respectively, freelists per pool.
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*/
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#define NCHUNKS_ORDER 6
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#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
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#define CHUNK_SIZE (1 << CHUNK_SHIFT)
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#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
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#define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
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#define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
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#define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
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#define BUDDY_MASK (0x3)
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/**
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* struct z3fold_pool - stores metadata for each z3fold pool
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* @lock: protects all pool fields and first|last_chunk fields of any
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* z3fold page in the pool
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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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* @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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* @ops: pointer to a structure of user defined operations specified at
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* pool creation time.
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*
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* This structure is allocated at pool creation time and maintains metadata
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* pertaining to a particular z3fold pool.
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*/
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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 lru;
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atomic64_t pages_nr;
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const struct z3fold_ops *ops;
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struct zpool *zpool;
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const struct zpool_ops *zpool_ops;
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};
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/*
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* Internal z3fold page flags
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*/
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enum z3fold_page_flags {
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PAGE_HEADLESS = 0,
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MIDDLE_CHUNK_MAPPED,
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};
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/*****************
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* Helpers
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*****************/
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/* Converts an allocation size in bytes to size in z3fold chunks */
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static int size_to_chunks(size_t size)
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{
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return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
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}
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#define for_each_unbuddied_list(_iter, _begin) \
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for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
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/* Initializes the z3fold header of a newly allocated z3fold page */
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static struct z3fold_header *init_z3fold_page(struct page *page)
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{
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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(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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zhdr->first_num = 0;
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zhdr->start_middle = 0;
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INIT_LIST_HEAD(&zhdr->buddy);
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return zhdr;
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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 page *page)
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{
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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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static inline void z3fold_page_lock(struct z3fold_header *zhdr)
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{
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spin_lock(&zhdr->page_lock);
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}
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/* Try to lock a z3fold page */
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static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
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{
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return spin_trylock(&zhdr->page_lock);
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}
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/* Unlock a z3fold page */
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static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
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{
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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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*/
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static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
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{
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unsigned long handle;
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handle = (unsigned long)zhdr;
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if (bud != HEADLESS)
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handle += (bud + zhdr->first_num) & BUDDY_MASK;
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return handle;
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}
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/* Returns the z3fold page where a given handle is stored */
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static struct z3fold_header *handle_to_z3fold_header(unsigned long handle)
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{
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return (struct z3fold_header *)(handle & PAGE_MASK);
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}
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/*
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* (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
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* but that doesn't matter. because the masking will result in the
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* correct buddy number.
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*/
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static enum buddy handle_to_buddy(unsigned long handle)
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{
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struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
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return (handle - zhdr->first_num) & BUDDY_MASK;
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}
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/*
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* Returns the number of free chunks in a z3fold page.
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* NB: can't be used with HEADLESS pages.
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*/
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static int num_free_chunks(struct z3fold_header *zhdr)
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{
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int nfree;
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/*
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* If there is a middle object, pick up the bigger free space
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* either before or after it. Otherwise just subtract the number
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* of chunks occupied by the first and the last objects.
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*/
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if (zhdr->middle_chunks != 0) {
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int nfree_before = zhdr->first_chunks ?
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0 : zhdr->start_middle - ZHDR_CHUNKS;
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int nfree_after = zhdr->last_chunks ?
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0 : TOTAL_CHUNKS -
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(zhdr->start_middle + zhdr->middle_chunks);
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nfree = max(nfree_before, nfree_after);
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} else
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nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
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return nfree;
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}
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/*****************
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* API Functions
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*****************/
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/**
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* z3fold_create_pool() - create a new z3fold pool
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* @gfp: gfp flags when allocating the z3fold pool structure
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* @ops: user-defined operations for the z3fold pool
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*
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* Return: pointer to the new z3fold pool or NULL if the metadata allocation
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* failed.
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*/
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static struct z3fold_pool *z3fold_create_pool(gfp_t gfp,
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const struct z3fold_ops *ops)
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{
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struct z3fold_pool *pool;
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int i;
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pool = kzalloc(sizeof(struct z3fold_pool), gfp);
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if (!pool)
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return NULL;
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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->lru);
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atomic64_set(&pool->pages_nr, 0);
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pool->ops = ops;
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return pool;
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}
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/**
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* z3fold_destroy_pool() - destroys an existing z3fold pool
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* @pool: the z3fold pool to be destroyed
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*
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* The pool should be emptied before this function is called.
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*/
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static void z3fold_destroy_pool(struct z3fold_pool *pool)
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{
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kfree(pool);
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}
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static inline void *mchunk_memmove(struct z3fold_header *zhdr,
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unsigned short dst_chunk)
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{
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void *beg = zhdr;
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return memmove(beg + (dst_chunk << CHUNK_SHIFT),
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beg + (zhdr->start_middle << CHUNK_SHIFT),
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zhdr->middle_chunks << CHUNK_SHIFT);
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}
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#define BIG_CHUNK_GAP 3
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/* Has to be called with lock held */
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static int z3fold_compact_page(struct z3fold_header *zhdr)
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{
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struct page *page = virt_to_page(zhdr);
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if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
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return 0; /* can't move middle chunk, it's used */
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if (zhdr->middle_chunks == 0)
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return 0; /* nothing to compact */
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if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
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/* move to the beginning */
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mchunk_memmove(zhdr, ZHDR_CHUNKS);
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zhdr->first_chunks = zhdr->middle_chunks;
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zhdr->middle_chunks = 0;
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zhdr->start_middle = 0;
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zhdr->first_num++;
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return 1;
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}
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/*
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* moving data is expensive, so let's only do that if
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* there's substantial gain (at least BIG_CHUNK_GAP chunks)
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*/
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if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
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zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
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BIG_CHUNK_GAP) {
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mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
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zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
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return 1;
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} else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
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TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
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+ zhdr->middle_chunks) >=
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BIG_CHUNK_GAP) {
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unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
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zhdr->middle_chunks;
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mchunk_memmove(zhdr, new_start);
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zhdr->start_middle = new_start;
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return 1;
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}
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return 0;
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}
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/**
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* z3fold_alloc() - allocates a region of a given size
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* @pool: z3fold pool from which to allocate
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* @size: size in bytes of the desired allocation
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* @gfp: gfp flags used if the pool needs to grow
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* @handle: handle of the new allocation
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*
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* This function will attempt to find a free region in the pool large enough to
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* satisfy the allocation request. A search of the unbuddied lists is
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* performed first. If no suitable free region is found, then a new page is
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* allocated and added to the pool to satisfy the request.
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*
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* gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
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* as z3fold pool pages.
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*
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* Return: 0 if success and handle is set, otherwise -EINVAL if the size or
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* gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
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* a new page.
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*/
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static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
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unsigned long *handle)
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{
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int chunks = 0, i, freechunks;
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struct z3fold_header *zhdr = NULL;
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enum buddy bud;
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struct page *page;
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if (!size || (gfp & __GFP_HIGHMEM))
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return -EINVAL;
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if (size > PAGE_SIZE)
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return -ENOSPC;
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if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
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bud = HEADLESS;
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else {
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chunks = size_to_chunks(size);
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/* First, try to find an unbuddied z3fold page. */
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zhdr = NULL;
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for_each_unbuddied_list(i, chunks) {
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spin_lock(&pool->lock);
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zhdr = list_first_entry_or_null(&pool->unbuddied[i],
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struct z3fold_header, buddy);
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if (!zhdr || !z3fold_page_trylock(zhdr)) {
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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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page = virt_to_page(zhdr);
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if (zhdr->first_chunks == 0) {
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if (zhdr->middle_chunks != 0 &&
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chunks >= zhdr->start_middle)
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bud = LAST;
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else
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bud = FIRST;
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} else if (zhdr->last_chunks == 0)
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bud = LAST;
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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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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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}
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goto found;
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}
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bud = FIRST;
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}
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/* Couldn't find unbuddied z3fold page, create new one */
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page = alloc_page(gfp);
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if (!page)
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return -ENOMEM;
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atomic64_inc(&pool->pages_nr);
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zhdr = init_z3fold_page(page);
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if (bud == HEADLESS) {
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set_bit(PAGE_HEADLESS, &page->private);
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spin_lock(&pool->lock);
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goto headless;
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}
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z3fold_page_lock(zhdr);
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found:
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if (bud == FIRST)
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zhdr->first_chunks = chunks;
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else if (bud == LAST)
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zhdr->last_chunks = chunks;
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else {
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zhdr->middle_chunks = chunks;
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zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
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}
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spin_lock(&pool->lock);
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if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
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zhdr->middle_chunks == 0) {
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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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}
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headless:
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/* Add/move z3fold page to beginning of LRU */
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if (!list_empty(&page->lru))
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list_del(&page->lru);
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list_add(&page->lru, &pool->lru);
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*handle = encode_handle(zhdr, bud);
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spin_unlock(&pool->lock);
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if (bud != HEADLESS)
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z3fold_page_unlock(zhdr);
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return 0;
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}
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/**
|
|
* z3fold_free() - frees the allocation associated with the given handle
|
|
* @pool: pool in which the allocation resided
|
|
* @handle: handle associated with the allocation returned by z3fold_alloc()
|
|
*
|
|
* In the case that the z3fold 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 z3fold_reclaim_page() below).
|
|
*/
|
|
static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
|
|
{
|
|
struct z3fold_header *zhdr;
|
|
int freechunks;
|
|
struct page *page;
|
|
enum buddy bud;
|
|
|
|
zhdr = handle_to_z3fold_header(handle);
|
|
page = virt_to_page(zhdr);
|
|
|
|
if (test_bit(PAGE_HEADLESS, &page->private)) {
|
|
/* HEADLESS page stored */
|
|
bud = HEADLESS;
|
|
} else {
|
|
z3fold_page_lock(zhdr);
|
|
bud = handle_to_buddy(handle);
|
|
|
|
switch (bud) {
|
|
case FIRST:
|
|
zhdr->first_chunks = 0;
|
|
break;
|
|
case MIDDLE:
|
|
zhdr->middle_chunks = 0;
|
|
zhdr->start_middle = 0;
|
|
break;
|
|
case LAST:
|
|
zhdr->last_chunks = 0;
|
|
break;
|
|
default:
|
|
pr_err("%s: unknown bud %d\n", __func__, bud);
|
|
WARN_ON(1);
|
|
z3fold_page_unlock(zhdr);
|
|
return;
|
|
}
|
|
}
|
|
|
|
if (bud == HEADLESS) {
|
|
spin_lock(&pool->lock);
|
|
list_del(&page->lru);
|
|
spin_unlock(&pool->lock);
|
|
free_z3fold_page(page);
|
|
atomic64_dec(&pool->pages_nr);
|
|
} else {
|
|
if (zhdr->first_chunks != 0 || zhdr->middle_chunks != 0 ||
|
|
zhdr->last_chunks != 0) {
|
|
z3fold_compact_page(zhdr);
|
|
/* Add to the unbuddied list */
|
|
spin_lock(&pool->lock);
|
|
if (!list_empty(&zhdr->buddy))
|
|
list_del(&zhdr->buddy);
|
|
freechunks = num_free_chunks(zhdr);
|
|
list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
|
|
spin_unlock(&pool->lock);
|
|
}
|
|
z3fold_page_unlock(zhdr);
|
|
spin_lock(&pool->lock);
|
|
if (kref_put(&zhdr->refcount, release_z3fold_page))
|
|
atomic64_dec(&pool->pages_nr);
|
|
spin_unlock(&pool->lock);
|
|
}
|
|
|
|
}
|
|
|
|
/**
|
|
* z3fold_reclaim_page() - evicts allocations from a pool page and frees it
|
|
* @pool: pool from which a page will attempt to be evicted
|
|
* @retires: number of pages on the LRU list for which eviction will
|
|
* be attempted before failing
|
|
*
|
|
* z3fold reclaim is different from normal system reclaim in that it is done
|
|
* from the bottom, up. This is because only the bottom layer, z3fold, has
|
|
* information on how the allocations are organized within each z3fold page.
|
|
* This has the potential to create interesting locking situations between
|
|
* z3fold and the user, however.
|
|
*
|
|
* To avoid these, this is how z3fold_reclaim_page() should be called:
|
|
|
|
* The user detects a page should be reclaimed and calls z3fold_reclaim_page().
|
|
* z3fold_reclaim_page() will remove a z3fold 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. z3fold_reclaim_page() will add the z3fold page back to the
|
|
* appropriate list and try the next z3fold 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 z3fold_free() on the handle. z3fold_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 z3fold page are successfully evicted, then the
|
|
* z3fold 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 z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
|
|
{
|
|
int i, ret = 0, freechunks;
|
|
struct z3fold_header *zhdr;
|
|
struct page *page;
|
|
unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
|
|
|
|
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);
|
|
return -EINVAL;
|
|
}
|
|
page = list_last_entry(&pool->lru, struct page, lru);
|
|
list_del_init(&page->lru);
|
|
|
|
zhdr = page_address(page);
|
|
if (!test_bit(PAGE_HEADLESS, &page->private)) {
|
|
if (!list_empty(&zhdr->buddy))
|
|
list_del_init(&zhdr->buddy);
|
|
kref_get(&zhdr->refcount);
|
|
spin_unlock(&pool->lock);
|
|
z3fold_page_lock(zhdr);
|
|
/*
|
|
* 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;
|
|
middle_handle = 0;
|
|
if (zhdr->first_chunks)
|
|
first_handle = encode_handle(zhdr, FIRST);
|
|
if (zhdr->middle_chunks)
|
|
middle_handle = encode_handle(zhdr, MIDDLE);
|
|
if (zhdr->last_chunks)
|
|
last_handle = encode_handle(zhdr, LAST);
|
|
z3fold_page_unlock(zhdr);
|
|
} else {
|
|
first_handle = encode_handle(zhdr, HEADLESS);
|
|
last_handle = middle_handle = 0;
|
|
spin_unlock(&pool->lock);
|
|
}
|
|
|
|
/* Issue the eviction callback(s) */
|
|
if (middle_handle) {
|
|
ret = pool->ops->evict(pool, middle_handle);
|
|
if (ret)
|
|
goto next;
|
|
}
|
|
if (first_handle) {
|
|
ret = pool->ops->evict(pool, first_handle);
|
|
if (ret)
|
|
goto next;
|
|
}
|
|
if (last_handle) {
|
|
ret = pool->ops->evict(pool, last_handle);
|
|
if (ret)
|
|
goto next;
|
|
}
|
|
next:
|
|
if (test_bit(PAGE_HEADLESS, &page->private)) {
|
|
if (ret == 0) {
|
|
free_z3fold_page(page);
|
|
return 0;
|
|
} else {
|
|
spin_lock(&pool->lock);
|
|
}
|
|
} else {
|
|
z3fold_page_lock(zhdr);
|
|
if ((zhdr->first_chunks || zhdr->last_chunks ||
|
|
zhdr->middle_chunks) &&
|
|
!(zhdr->first_chunks && zhdr->last_chunks &&
|
|
zhdr->middle_chunks)) {
|
|
z3fold_compact_page(zhdr);
|
|
/* add to unbuddied list */
|
|
spin_lock(&pool->lock);
|
|
freechunks = num_free_chunks(zhdr);
|
|
list_add(&zhdr->buddy,
|
|
&pool->unbuddied[freechunks]);
|
|
spin_unlock(&pool->lock);
|
|
}
|
|
z3fold_page_unlock(zhdr);
|
|
spin_lock(&pool->lock);
|
|
if (kref_put(&zhdr->refcount, release_z3fold_page)) {
|
|
spin_unlock(&pool->lock);
|
|
atomic64_dec(&pool->pages_nr);
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Add to the beginning of LRU.
|
|
* Pool lock has to be kept here to ensure the page has
|
|
* not already been released
|
|
*/
|
|
list_add(&page->lru, &pool->lru);
|
|
}
|
|
spin_unlock(&pool->lock);
|
|
return -EAGAIN;
|
|
}
|
|
|
|
/**
|
|
* z3fold_map() - maps the allocation associated with the given handle
|
|
* @pool: pool in which the allocation resides
|
|
* @handle: handle associated with the allocation to be mapped
|
|
*
|
|
* Extracts the buddy number from handle and constructs the pointer to the
|
|
* correct starting chunk within the page.
|
|
*
|
|
* Returns: a pointer to the mapped allocation
|
|
*/
|
|
static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
|
|
{
|
|
struct z3fold_header *zhdr;
|
|
struct page *page;
|
|
void *addr;
|
|
enum buddy buddy;
|
|
|
|
zhdr = handle_to_z3fold_header(handle);
|
|
addr = zhdr;
|
|
page = virt_to_page(zhdr);
|
|
|
|
if (test_bit(PAGE_HEADLESS, &page->private))
|
|
goto out;
|
|
|
|
z3fold_page_lock(zhdr);
|
|
buddy = handle_to_buddy(handle);
|
|
switch (buddy) {
|
|
case FIRST:
|
|
addr += ZHDR_SIZE_ALIGNED;
|
|
break;
|
|
case MIDDLE:
|
|
addr += zhdr->start_middle << CHUNK_SHIFT;
|
|
set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
|
|
break;
|
|
case LAST:
|
|
addr += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
|
|
break;
|
|
default:
|
|
pr_err("unknown buddy id %d\n", buddy);
|
|
WARN_ON(1);
|
|
addr = NULL;
|
|
break;
|
|
}
|
|
|
|
z3fold_page_unlock(zhdr);
|
|
out:
|
|
return addr;
|
|
}
|
|
|
|
/**
|
|
* z3fold_unmap() - unmaps the allocation associated with the given handle
|
|
* @pool: pool in which the allocation resides
|
|
* @handle: handle associated with the allocation to be unmapped
|
|
*/
|
|
static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
|
|
{
|
|
struct z3fold_header *zhdr;
|
|
struct page *page;
|
|
enum buddy buddy;
|
|
|
|
zhdr = handle_to_z3fold_header(handle);
|
|
page = virt_to_page(zhdr);
|
|
|
|
if (test_bit(PAGE_HEADLESS, &page->private))
|
|
return;
|
|
|
|
z3fold_page_lock(zhdr);
|
|
buddy = handle_to_buddy(handle);
|
|
if (buddy == MIDDLE)
|
|
clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
|
|
z3fold_page_unlock(zhdr);
|
|
}
|
|
|
|
/**
|
|
* z3fold_get_pool_size() - gets the z3fold pool size in pages
|
|
* @pool: pool whose size is being queried
|
|
*
|
|
* Returns: size in pages of the given pool.
|
|
*/
|
|
static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
|
|
{
|
|
return atomic64_read(&pool->pages_nr);
|
|
}
|
|
|
|
/*****************
|
|
* 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(gfp, zpool_ops ? &z3fold_zpool_ops : NULL);
|
|
if (pool) {
|
|
pool->zpool = zpool;
|
|
pool->zpool_ops = zpool_ops;
|
|
}
|
|
return pool;
|
|
}
|
|
|
|
static void z3fold_zpool_destroy(void *pool)
|
|
{
|
|
z3fold_destroy_pool(pool);
|
|
}
|
|
|
|
static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
|
|
unsigned long *handle)
|
|
{
|
|
return z3fold_alloc(pool, size, gfp, handle);
|
|
}
|
|
static void z3fold_zpool_free(void *pool, unsigned long handle)
|
|
{
|
|
z3fold_free(pool, handle);
|
|
}
|
|
|
|
static int z3fold_zpool_shrink(void *pool, unsigned int pages,
|
|
unsigned int *reclaimed)
|
|
{
|
|
unsigned int total = 0;
|
|
int ret = -EINVAL;
|
|
|
|
while (total < pages) {
|
|
ret = z3fold_reclaim_page(pool, 8);
|
|
if (ret < 0)
|
|
break;
|
|
total++;
|
|
}
|
|
|
|
if (reclaimed)
|
|
*reclaimed = total;
|
|
|
|
return ret;
|
|
}
|
|
|
|
static void *z3fold_zpool_map(void *pool, unsigned long handle,
|
|
enum zpool_mapmode mm)
|
|
{
|
|
return z3fold_map(pool, handle);
|
|
}
|
|
static void z3fold_zpool_unmap(void *pool, unsigned long handle)
|
|
{
|
|
z3fold_unmap(pool, handle);
|
|
}
|
|
|
|
static u64 z3fold_zpool_total_size(void *pool)
|
|
{
|
|
return z3fold_get_pool_size(pool) * PAGE_SIZE;
|
|
}
|
|
|
|
static struct zpool_driver z3fold_zpool_driver = {
|
|
.type = "z3fold",
|
|
.owner = THIS_MODULE,
|
|
.create = z3fold_zpool_create,
|
|
.destroy = z3fold_zpool_destroy,
|
|
.malloc = z3fold_zpool_malloc,
|
|
.free = z3fold_zpool_free,
|
|
.shrink = z3fold_zpool_shrink,
|
|
.map = z3fold_zpool_map,
|
|
.unmap = z3fold_zpool_unmap,
|
|
.total_size = z3fold_zpool_total_size,
|
|
};
|
|
|
|
MODULE_ALIAS("zpool-z3fold");
|
|
|
|
static int __init init_z3fold(void)
|
|
{
|
|
/* Make sure the z3fold header is not larger than the page size */
|
|
BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
|
|
zpool_register_driver(&z3fold_zpool_driver);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void __exit exit_z3fold(void)
|
|
{
|
|
zpool_unregister_driver(&z3fold_zpool_driver);
|
|
}
|
|
|
|
module_init(init_z3fold);
|
|
module_exit(exit_z3fold);
|
|
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
|
|
MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");
|