litmus-rt.git - The LITMUS^RT kernel.

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author	Mark Brown <broonie@kernel.org>	2015-02-05 14:36:29 -0500
committer	Mark Brown <broonie@kernel.org>	2015-02-05 14:36:29 -0500
commit	c503ca52a57cfe24f8937ca145a96ba94f6bb112 (patch)
tree	870d4f44e6c17f25f426bf662fb8fdf466b6e264 /arch/x86/mm/fault.c
parent	b2dde2f975a7850b696c21253864fd93c1753e7c (diff)
parent	fddcd300732dad5b822d27de7aa78998dca43162 (diff)

Merge remote-tracking branch 'asoc/fix/samsung' into asoc-linus

Diffstat (limited to 'arch/x86/mm/fault.c')

0 files changed, 0 insertions, 0 deletions

/* * zbud.c * * Copyright (C) 2013, Seth Jennings, IBM * * Concepts based on zcache internal zbud allocator by Dan Magenheimer. * * zbud is an special purpose allocator for storing compressed pages. Contrary * to what its name may suggest, zbud is not a buddy allocator, but rather an * allocator that "buddies" two compressed pages together in a single memory * page. * * While this design limits storage density, it has simple and deterministic * reclaim properties that make it preferable to a higher density approach when * reclaim will be used. * * zbud works by storing compressed pages, or "zpages", together in pairs in a * single memory page called a "zbud page". The first buddy is "left * justified" at the beginning of the zbud page, and the last buddy is "right * justified" at the end of the zbud page. The benefit is that if either * buddy is freed, the freed buddy space, coalesced with whatever slack space * that existed between the buddies, results in the largest possible free region * within the zbud page. * * zbud also provides an attractive lower bound on density. The ratio of zpages * to zbud pages can not be less than 1. This ensures that zbud can never "do * harm" by using more pages to store zpages than the uncompressed zpages would * have used on their own. * * zbud pages are divided into "chunks". The size of the chunks is fixed at * compile time and determined by NCHUNKS_ORDER below. Dividing zbud pages * into chunks allows organizing unbuddied zbud pages into a manageable number * of unbuddied lists according to the number of free chunks available in the * zbud page. * * The zbud API differs from that of conventional allocators in that the * allocation function, zbud_alloc(), returns an opaque handle to the user, * not a dereferenceable pointer. The user must map the handle using * zbud_map() in order to get a usable pointer by which to access the * allocation data and unmap the handle with zbud_unmap() when operations * on the allocation data are complete. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/atomic.h> #include <linux/list.h> #include <linux/mm.h> #include <linux/module.h> #include <linux/preempt.h> #include <linux/slab.h> #include <linux/spinlock.h> #include <linux/zbud.h> #include <linux/zpool.h> /***************** * Structures *****************/ /* * NCHUNKS_ORDER determines the internal allocation granularity, effectively * adjusting internal fragmentation. It also determines the number of * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the * allocation granularity will be in chunks of size PAGE_SIZE/64, and there * will be 64 freelists per pool. */ #define NCHUNKS_ORDER 6 #define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER) #define CHUNK_SIZE (1 << CHUNK_SHIFT) #define NCHUNKS (PAGE_SIZE >> CHUNK_SHIFT) #define ZHDR_SIZE_ALIGNED CHUNK_SIZE /** * struct zbud_pool - stores metadata for each zbud pool * @lock: protects all pool fields and first|last_chunk fields of any * zbud page in the pool * @unbuddied: array of lists tracking zbud pages that only contain one buddy; * the lists each zbud page is added to depends on the size of * 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. * @ops: pointer to a structure of user defined operations specified at * pool creation time. * * This structure is allocated at pool creation time and maintains metadata * pertaining to a particular zbud pool. */ struct zbud_pool { spinlock_t lock; struct list_head unbuddied[NCHUNKS]; struct list_head buddied; struct list_head lru; u64 pages_nr; struct zbud_ops *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; }; /***************** * zpool ****************/ #ifdef CONFIG_ZPOOL static int zbud_zpool_evict(struct zbud_pool *pool, unsigned long handle) { return zpool_evict(pool, handle); } static struct zbud_ops zbud_zpool_ops = { .evict = zbud_zpool_evict }; static void *zbud_zpool_create(gfp_t gfp, struct zpool_ops *zpool_ops) { return zbud_create_pool(gfp, &zbud_zpool_ops); } static void zbud_zpool_destroy(void *pool) { zbud_destroy_pool(pool); } static int zbud_zpool_malloc(void *pool, size_t size, gfp_t gfp, unsigned long *handle) { return zbud_alloc(pool, size, gfp, handle); } static void zbud_zpool_free(void *pool, unsigned long handle) { 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) { return zbud_map(pool, handle); } static void zbud_zpool_unmap(void *pool, unsigned long handle) { zbud_unmap(pool, handle); } static u64 zbud_zpool_total_size(void *pool) { return zbud_get_pool_size(pool) * PAGE_SIZE; } static struct zpool_driver zbud_zpool_driver = { .type = "zbud", .owner = THIS_MODULE, .create = zbud_zpool_create, .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, }; MODULE_ALIAS("zpool-zbud"); #endif /* CONFIG_ZPOOL */ /***************** * Helpers *****************/ /* Just to make the code easier to read */ enum buddy { FIRST, LAST }; /* Converts an allocation size in bytes to size in zbud chunks */ static int size_to_chunks(size_t size) { return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT; } #define for_each_unbuddied_list(_iter, _begin) \ for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++) /* Initializes the zbud header of a newly allocated zbud page */ static struct zbud_header *init_zbud_page(struct page *page) { struct zbud_header *zhdr = page_address(page); zhdr->first_chunks = 0; zhdr->last_chunks = 0; INIT_LIST_HEAD(&zhdr->buddy); INIT_LIST_HEAD(&zhdr->lru); zhdr->under_reclaim = 0; return zhdr; } /* Resets the struct page fields and frees the page */ static void free_zbud_page(struct zbud_header *zhdr) { __free_page(virt_to_page(zhdr)); } /* * Encodes the handle of a particular buddy within a zbud page * Pool lock should be held as this function accesses first|last_chunks */ static unsigned long encode_handle(struct zbud_header *zhdr, enum buddy bud) { unsigned long handle; /* * For now, the encoded handle is actually just the pointer to the data * but this might not always be the case. A little information hiding. * Add CHUNK_SIZE to the handle if it is the first allocation to jump * over the zbud header in the first chunk. */ handle = (unsigned long)zhdr; if (bud == FIRST) /* skip over zbud header */ handle += ZHDR_SIZE_ALIGNED; else /* bud == LAST */ handle += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT); return handle; } /* Returns the zbud page where a given handle is stored */ static struct zbud_header *handle_to_zbud_header(unsigned long handle) { return (struct zbud_header *)(handle & PAGE_MASK); } /* Returns the number of free chunks in a zbud page */ static int num_free_chunks(struct zbud_header *zhdr) { /* * Rather than branch for different situations, just use the fact that * free buddies have a length of zero to simplify everything. -1 at the * end for the zbud header. */ return NCHUNKS - zhdr->first_chunks - zhdr->last_chunks - 1; } /***************** * API Functions *****************/ /** * 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. */ struct zbud_pool *zbud_create_pool(gfp_t gfp, struct zbud_ops *ops) { struct zbud_pool *pool; int i; pool = kmalloc(sizeof(struct zbud_pool), gfp); if (!pool) return NULL; spin_lock_init(&pool->lock); 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; pool->ops = ops; return pool; } /** * zbud_destroy_pool() - destroys an existing zbud pool * @pool: the zbud pool to be destroyed * * The pool should be emptied before this function is called. */ void zbud_destroy_pool(struct zbud_pool *pool) { kfree(pool); } /** * zbud_alloc() - allocates a region of a given size * @pool: zbud pool from which to allocate * @size: size in bytes of the desired allocation * @gfp: gfp flags used if the pool needs to grow * @handle: handle of the new allocation * * This function will attempt to find a free region in the pool large enough to * satisfy the allocation request. A search of the unbuddied lists is * performed first. If no suitable free region is found, then a new page is * allocated and added to the pool to satisfy the request. * * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used * as zbud pool pages. * * Return: 0 if success and handle is set, otherwise -EINVAL if the size or * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate * a new page. */ int zbud_alloc(struct zbud_pool *pool, size_t size, gfp_t gfp, unsigned long *handle) { int chunks, i, freechunks; struct zbud_header *zhdr = NULL; enum buddy bud; struct page *page; if (!size || (gfp & __GFP_HIGHMEM)) return -EINVAL; if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE) return -ENOSPC; chunks = size_to_chunks(size); spin_lock(&pool->lock); /* First, try to find an unbuddied zbud page. */ zhdr = NULL; for_each_unbuddied_list(i, chunks) { if (!list_empty(&pool->unbuddied[i])) { zhdr = list_first_entry(&pool->unbuddied[i], struct zbud_header, buddy); list_del(&zhdr->buddy); if (zhdr->first_chunks == 0) bud = FIRST; else bud = LAST; goto found; } } /* Couldn't find unbuddied zbud page, create new one */ spin_unlock(&pool->lock); page = alloc_page(gfp); if (!page) return -ENOMEM; spin_lock(&pool->lock); pool->pages_nr++; zhdr = init_zbud_page(page); bud = FIRST; found: if (bud == FIRST) zhdr->first_chunks = chunks; else zhdr->last_chunks = chunks; 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 */


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