/* * Copyright (C) 2009-2011 Red Hat, Inc. * * Author: Mikulas Patocka <mpatocka@redhat.com> * * This file is released under the GPL. */ #include "dm-bufio.h" #include <linux/device-mapper.h> #include <linux/dm-io.h> #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/version.h> #include <linux/shrinker.h> #include <linux/module.h> #define DM_MSG_PREFIX "bufio" /* * Memory management policy: * Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory * or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower). * Always allocate at least DM_BUFIO_MIN_BUFFERS buffers. * Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT * dirty buffers. */ #define DM_BUFIO_MIN_BUFFERS 8 #define DM_BUFIO_MEMORY_PERCENT 2 #define DM_BUFIO_VMALLOC_PERCENT 25 #define DM_BUFIO_WRITEBACK_PERCENT 75 /* * Check buffer ages in this interval (seconds) */ #define DM_BUFIO_WORK_TIMER_SECS 10 /* * Free buffers when they are older than this (seconds) */ #define DM_BUFIO_DEFAULT_AGE_SECS 60 /* * The number of bvec entries that are embedded directly in the buffer. * If the chunk size is larger, dm-io is used to do the io. */ #define DM_BUFIO_INLINE_VECS 16 /* * Buffer hash */ #define DM_BUFIO_HASH_BITS 20 #define DM_BUFIO_HASH(block) \ ((((block) >> DM_BUFIO_HASH_BITS) ^ (block)) & \ ((1 << DM_BUFIO_HASH_BITS) - 1)) /* * Don't try to use kmem_cache_alloc for blocks larger than this. * For explanation, see alloc_buffer_data below. */ #define DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT (PAGE_SIZE >> 1) #define DM_BUFIO_BLOCK_SIZE_GFP_LIMIT (PAGE_SIZE << (MAX_ORDER - 1)) /* * dm_buffer->list_mode */ #define LIST_CLEAN 0 #define LIST_DIRTY 1 #define LIST_SIZE 2 /* * Linking of buffers: * All buffers are linked to cache_hash with their hash_list field. * * Clean buffers that are not being written (B_WRITING not set) * are linked to lru[LIST_CLEAN] with their lru_list field. * * Dirty and clean buffers that are being written are linked to * lru[LIST_DIRTY] with their lru_list field. When the write * finishes, the buffer cannot be relinked immediately (because we * are in an interrupt context and relinking requires process * context), so some clean-not-writing buffers can be held on * dirty_lru too. They are later added to lru in the process * context. */ struct dm_bufio_client { struct mutex lock; struct list_head lru[LIST_SIZE]; unsigned long n_buffers[LIST_SIZE]; struct block_device *bdev; unsigned block_size; unsigned char sectors_per_block_bits; unsigned char pages_per_block_bits; unsigned char blocks_per_page_bits; unsigned aux_size; void (*alloc_callback)(struct dm_buffer *); void (*write_callback)(struct dm_buffer *); struct dm_io_client *dm_io; struct list_head reserved_buffers; unsigned need_reserved_buffers; struct hlist_head *cache_hash; wait_queue_head_t free_buffer_wait; int async_write_error; struct list_head client_list; struct shrinker shrinker; }; /* * Buffer state bits. */ #define B_READING 0 #define B_WRITING 1 #define B_DIRTY 2 /* * Describes how the block was allocated: * kmem_cache_alloc(), __get_free_pages() or vmalloc(). * See the comment at alloc_buffer_data. */ enum data_mode { DATA_MODE_SLAB = 0, DATA_MODE_GET_FREE_PAGES = 1, DATA_MODE_VMALLOC = 2, DATA_MODE_LIMIT = 3 }; struct dm_buffer { struct hlist_node hash_list; struct list_head lru_list; sector_t block; void *data; enum data_mode data_mode; unsigned char list_mode; /* LIST_* */ unsigned hold_count; int read_error; int write_error; unsigned long state; unsigned long last_accessed; struct dm_bufio_client *c; struct bio bio; struct bio_vec bio_vec[DM_BUFIO_INLINE_VECS]; }; /*----------------------------------------------------------------*/ static struct kmem_cache *dm_bufio_caches[PAGE_SHIFT - SECTOR_SHIFT]; static char *dm_bufio_cache_names[PAGE_SHIFT - SECTOR_SHIFT]; static inline int dm_bufio_cache_index(struct dm_bufio_client *c) { unsigned ret = c->blocks_per_page_bits - 1; BUG_ON(ret >= ARRAY_SIZE(dm_bufio_caches)); return ret; } #define DM_BUFIO_CACHE(c) (dm_bufio_caches[dm_bufio_cache_index(c)]) #define DM_BUFIO_CACHE_NAME(c) (dm_bufio_cache_names[dm_bufio_cache_index(c)]) #define dm_bufio_in_request() (!!current->bio_list) static void dm_bufio_lock(struct dm_bufio_client *c) { mutex_lock_nested(&c->lock, dm_bufio_in_request()); } static int dm_bufio_trylock(struct dm_bufio_client *c) { return mutex_trylock(&c->lock); } static void dm_bufio_unlock(struct dm_bufio_client *c) { mutex_unlock(&c->lock); } /* * FIXME Move to sched.h? */ #ifdef CONFIG_PREEMPT_VOLUNTARY # define dm_bufio_cond_resched() \ do { \ if (unlikely(need_resched())) \ _cond_resched(); \ } while (0) #else # define dm_bufio_cond_resched() do { } while (0) #endif /*----------------------------------------------------------------*/ /* * Default cache size: available memory divided by the ratio. */ static unsigned long dm_bufio_default_cache_size; /* * Total cache size set by the user. */ static unsigned long dm_bufio_cache_size; /* * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change * at any time. If it disagrees, the user has changed cache size. */ static unsigned long dm_bufio_cache_size_latch; static DEFINE_SPINLOCK(param_spinlock); /* * Buffers are freed after this timeout */ static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS; static unsigned long dm_bufio_peak_allocated; static unsigned long dm_bufio_allocated_kmem_cache; static unsigned long dm_bufio_allocated_get_free_pages; static unsigned long dm_bufio_allocated_vmalloc; static unsigned long dm_bufio_current_allocated; /*----------------------------------------------------------------*/ /* * Per-client cache: dm_bufio_cache_size / dm_bufio_client_count */ static unsigned long dm_bufio_cache_size_per_client; /* * The current number of clients. */ static int dm_bufio_client_count; /* * The list of all clients. */ static LIST_HEAD(dm_bufio_all_clients); /* * This mutex protects dm_bufio_cache_size_latch, * dm_bufio_cache_size_per_client and dm_bufio_client_count */ static DEFINE_MUTEX(dm_bufio_clients_lock); /*----------------------------------------------------------------*/ static void adjust_total_allocated(enum data_mode data_mode, long diff) { static unsigned long * const class_ptr[DATA_MODE_LIMIT] = { &dm_bufio_allocated_kmem_cache, &dm_bufio_allocated_get_free_pages, &dm_bufio_allocated_vmalloc, }; spin_lock(¶m_spinlock); *class_ptr[data_mode] += diff; dm_bufio_current_allocated += diff; if (dm_bufio_current_allocated > dm_bufio_peak_allocated) dm_bufio_peak_allocated = dm_bufio_current_allocated; spin_unlock(¶m_spinlock); } /* * Change the number of clients and recalculate per-client limit. */ static void __cache_size_refresh(void) { BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock)); BUG_ON(dm_bufio_client_count < 0); dm_bufio_cache_size_latch = dm_bufio_cache_size; barrier(); /* * Use default if set to 0 and report the actual cache size used. */ if (!dm_bufio_cache_size_latch) { (void)cmpxchg(&dm_bufio_cache_size, 0, dm_bufio_default_cache_size); dm_bufio_cache_size_latch = dm_bufio_default_cache_size; } dm_bufio_cache_size_per_client = dm_bufio_cache_size_latch / (dm_bufio_client_count ? : 1); } /* * Allocating buffer data. * * Small buffers are allocated with kmem_cache, to use space optimally. * * For large buffers, we choose between get_free_pages and vmalloc. * Each has advantages and disadvantages. * * __get_free_pages can randomly fail if the memory is fragmented. * __vmalloc won't randomly fail, but vmalloc space is limited (it may be * as low as 128M) so using it for caching is not appropriate. * * If the allocation may fail we use __get_free_pages. Memory fragmentation * won't have a fatal effect here, but it just causes flushes of some other * buffers and more I/O will be performed. Don't use __get_free_pages if it * always fails (i.e. order >= MAX_ORDER). * * If the allocation shouldn't fail we use __vmalloc. This is only for the * initial reserve allocation, so there's no risk of wasting all vmalloc * space. */ static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask, enum data_mode *data_mode) { if (c->block_size <= DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT) { *data_mode = DATA_MODE_SLAB; return kmem_cache_alloc(DM_BUFIO_CACHE(c), gfp_mask); } if (c->block_size <= DM_BUFIO_BLOCK_SIZE_GFP_LIMIT && gfp_mask & __GFP_NORETRY) { *data_mode = DATA_MODE_GET_FREE_PAGES; return (void *)__get_free_pages(gfp_mask, c->pages_per_block_bits); } *data_mode = DATA_MODE_VMALLOC; return __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); } /* * Free buffer's data. */ static void free_buffer_data(struct dm_bufio_client *c, void *data, enum data_mode data_mode) { switch (data_mode) { case DATA_MODE_SLAB: kmem_cache_free(DM_BUFIO_CACHE(c), data); break; case DATA_MODE_GET_FREE_PAGES: free_pages((unsigned long)data, c->pages_per_block_bits); break; case DATA_MODE_VMALLOC: vfree(data); break; default: DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d", data_mode); BUG(); } } /* * Allocate buffer and its data. */ static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask) { struct dm_buffer *b = kmalloc(sizeof(struct dm_buffer) + c->aux_size, gfp_mask); if (!b) return NULL; b->c = c; b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode); if (!b->data) { kfree(b); return NULL; } adjust_total_allocated(b->data_mode, (long)c->block_size); return b; } /* * Free buffer and its data. */ static void free_buffer(struct dm_buffer *b) { struct dm_bufio_client *c = b->c; adjust_total_allocated(b->data_mode, -(long)c->block_size); free_buffer_data(c, b->data, b->data_mode); kfree(b); } /* * Link buffer to the hash list and clean or dirty queue. */ static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty) { struct dm_bufio_client *c = b->c; c->n_buffers[dirty]++; b->block = block; b->list_mode = dirty; list_add(&b->lru_list, &c->lru[dirty]); hlist_add_head(&b->hash_list, &c->cache_hash[DM_BUFIO_HASH(block)]); b->last_accessed = jiffies; } /* * Unlink buffer from the hash list and dirty or clean queue. */ static void __unlink_buffer(struct dm_buffer *b) { struct dm_bufio_client *c = b->c; BUG_ON(!c->n_buffers[b->list_mode]); c->n_buffers[b->list_mode]--; hlist_del(&b->hash_list); list_del(&b->lru_list); } /* * Place the buffer to the head of dirty or clean LRU queue. */ static void __relink_lru(struct dm_buffer *b, int dirty) { struct dm_bufio_client *c = b->c; BUG_ON(!c->n_buffers[b->list_mode]); c->n_buffers[b->list_mode]--; c->n_buffers[dirty]++; b->list_mode = dirty; list_del(&b->lru_list); list_add(&b->lru_list, &c->lru[dirty]); } /*---------------------------------------------------------------- * Submit I/O on the buffer. * * Bio interface is faster but it has some problems: * the vector list is limited (increasing this limit increases * memory-consumption per buffer, so it is not viable); * * the memory must be direct-mapped, not vmalloced; * * the I/O driver can reject requests spuriously if it thinks that * the requests are too big for the device or if they cross a * controller-defined memory boundary. * * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and * it is not vmalloced, try using the bio interface. * * If the buffer is big, if it is vmalloced or if the underlying device * rejects the bio because it is too large, use dm-io layer to do the I/O. * The dm-io layer splits the I/O into multiple requests, avoiding the above * shortcomings. *--------------------------------------------------------------*/ /* * dm-io completion routine. It just calls b->bio.bi_end_io, pretending * that the request was handled directly with bio interface. */ static void dmio_complete(unsigned long error, void *context) { struct dm_buffer *b = context; b->bio.bi_end_io(&b->bio, error ? -EIO : 0); } static void use_dmio(struct dm_buffer *b, int rw, sector_t block, bio_end_io_t *end_io) { int r; struct dm_io_request io_req = { .bi_rw = rw, .notify.fn = dmio_complete, .notify.context = b, .client = b->c->dm_io, }; struct dm_io_region region = { .bdev = b->c->bdev, .sector = block << b->c->sectors_per_block_bits, .count = b->c->block_size >> SECTOR_SHIFT, }; if (b->data_mode != DATA_MODE_VMALLOC) { io_req.mem.type = DM_IO_KMEM; io_req.mem.ptr.addr = b->data; } else { io_req.mem.type = DM_IO_VMA; io_req.mem.ptr.vma = b->data; } b->bio.bi_end_io = end_io; r = dm_io(&io_req, 1, ®ion, NULL); if (r) end_io(&b->bio, r); } static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block, bio_end_io_t *end_io) { char *ptr; int len; bio_init(&b->bio); b->bio.bi_io_vec = b->bio_vec; b->bio.bi_max_vecs = DM_BUFIO_INLINE_VECS; b->bio.bi_sector = block << b->c->sectors_per_block_bits; b->bio.bi_bdev = b->c->bdev; b->bio.bi_end_io = end_io; /* * We assume that if len >= PAGE_SIZE ptr is page-aligned. * If len < PAGE_SIZE the buffer doesn't cross page boundary. */ ptr = b->data; len = b->c->block_size; if (len >= PAGE_SIZE) BUG_ON((unsigned long)ptr & (PAGE_SIZE - 1)); else BUG_ON((unsigned long)ptr & (len - 1)); do { if (!bio_add_page(&b->bio, virt_to_page(ptr), len < PAGE_SIZE ? len : PAGE_SIZE, virt_to_phys(ptr) & (PAGE_SIZE - 1))) { BUG_ON(b->c->block_size <= PAGE_SIZE); use_dmio(b, rw, block, end_io); return; } len -= PAGE_SIZE; ptr += PAGE_SIZE; } while (len > 0); submit_bio(rw, &b->bio); } static void submit_io(struct dm_buffer *b, int rw, sector_t block, bio_end_io_t *end_io) { if (rw == WRITE && b->c->write_callback) b->c->write_callback(b); if (b->c->block_size <= DM_BUFIO_INLINE_VECS * PAGE_SIZE && b->data_mode != DATA_MODE_VMALLOC) use_inline_bio(b, rw, block, end_io); else use_dmio(b, rw, block, end_io); } /*---------------------------------------------------------------- * Writing dirty buffers *--------------------------------------------------------------*/ /* * The endio routine for write. * * Set the error, clear B_WRITING bit and wake anyone who was waiting on * it. */ static void write_endio(struct bio *bio, int error) { struct dm_buffer *b = container_of(bio, struct dm_buffer, bio); b->write_error = error; if (error) { struct dm_bufio_client *c = b->c; (void)cmpxchg(&c->async_write_error, 0, error); } BUG_ON(!test_bit(B_WRITING, &b->state)); smp_mb__before_clear_bit(); clear_bit(B_WRITING, &b->state); smp_mb__after_clear_bit(); wake_up_bit(&b->state, B_WRITING); } /* * This function is called when wait_on_bit is actually waiting. */ static int do_io_schedule(void *word) { io_schedule(); return 0; } /* * Initiate a write on a dirty buffer, but don't wait for it. * * - If the buffer is not dirty, exit. * - If there some previous write going on, wait for it to finish (we can't * have two writes on the same buffer simultaneously). * - Submit our write and don't wait on it. We set B_WRITING indicating * that there is a write in progress. */ static void __write_dirty_buffer(struct dm_buffer *b) { if (!test_bit(B_DIRTY, &b->state)) return; clear_bit(B_DIRTY, &b->state); wait_on_bit_lock(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE); submit_io(b, WRITE, b->block, write_endio); } /* * Wait until any activity on the buffer finishes. Possibly write the * buffer if it is dirty. When this function finishes, there is no I/O * running on the buffer and the buffer is not dirty. */ static void __make_buffer_clean(struct dm_buffer *b) { BUG_ON(b->hold_count); if (!b->state) /* fast case */ return; wait_on_bit(&b->state, B_READING, do_io_schedule, TASK_UNINTERRUPTIBLE); __write_dirty_buffer(b); wait_on_bit(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE); } /* * Find some buffer that is not held by anybody, clean it, unlink it and * return it. */ static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c) { struct dm_buffer *b; list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) { BUG_ON(test_bit(B_WRITING, &b->state)); BUG_ON(test_bit(B_DIRTY, &b->state)); if (!b->hold_count) { __make_buffer_clean(b); __unlink_buffer(b); return b; } dm_bufio_cond_resched(); } list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) { BUG_ON(test_bit(B_READING, &b->state)); if (!b->hold_count) { __make_buffer_clean(b); __unlink_buffer(b); return b; } dm_bufio_cond_resched(); } return NULL; } /* * Wait until some other threads free some buffer or release hold count on * some buffer. * * This function is entered with c->lock held, drops it and regains it * before exiting. */ static void __wait_for_free_buffer(struct dm_bufio_client *c) { DECLARE_WAITQUEUE(wait, current); add_wait_queue(&c->free_buffer_wait, &wait); set_task_state(current, TASK_UNINTERRUPTIBLE); dm_bufio_unlock(c); io_schedule(); set_task_state(current, TASK_RUNNING); remove_wait_queue(&c->free_buffer_wait, &wait); dm_bufio_lock(c); } /* * Allocate a new buffer. If the allocation is not possible, wait until * some other thread frees a buffer. * * May drop the lock and regain it. */ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c) { struct dm_buffer *b; /* * dm-bufio is resistant to allocation failures (it just keeps * one buffer reserved in cases all the allocations fail). * So set flags to not try too hard: * GFP_NOIO: don't recurse into the I/O layer * __GFP_NORETRY: don't retry and rather return failure * __GFP_NOMEMALLOC: don't use emergency reserves * __GFP_NOWARN: don't print a warning in case of failure * * For debugging, if we set the cache size to 1, no new buffers will * be allocated. */ while (1) { if (dm_bufio_cache_size_latch != 1) { b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); if (b) return b; } if (!list_empty(&c->reserved_buffers)) { b = list_entry(c->reserved_buffers.next, struct dm_buffer, lru_list); list_del(&b->lru_list); c->need_reserved_buffers++; return b; } b = __get_unclaimed_buffer(c); if (b) return b; __wait_for_free_buffer(c); } } static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c) { struct dm_buffer *b = __alloc_buffer_wait_no_callback(c); if (c->alloc_callback) c->alloc_callback(b); return b; } /* * Free a buffer and wake other threads waiting for free buffers. */ static void __free_buffer_wake(struct dm_buffer *b) { struct dm_bufio_client *c = b->c; if (!c->need_reserved_buffers) free_buffer(b); else { list_add(&b->lru_list, &c->reserved_buffers); c->need_reserved_buffers--; } wake_up(&c->free_buffer_wait); } static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait) { struct dm_buffer *b, *tmp; list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) { BUG_ON(test_bit(B_READING, &b->state)); if (!test_bit(B_DIRTY, &b->state) && !test_bit(B_WRITING, &b->state)) { __relink_lru(b, LIST_CLEAN); continue; } if (no_wait && test_bit(B_WRITING, &b->state)) return; __write_dirty_buffer(b); dm_bufio_cond_resched(); } } /* * Get writeback threshold and buffer limit for a given client. */ static void __get_memory_limit(struct dm_bufio_client *c, unsigned long *threshold_buffers, unsigned long *limit_buffers) { unsigned long buffers; if (dm_bufio_cache_size != dm_bufio_cache_size_latch) { mutex_lock(&dm_bufio_clients_lock); __cache_size_refresh(); mutex_unlock(&dm_bufio_clients_lock); } buffers = dm_bufio_cache_size_per_client >> (c->sectors_per_block_bits + SECTOR_SHIFT); if (buffers < DM_BUFIO_MIN_BUFFERS) buffers = DM_BUFIO_MIN_BUFFERS; *limit_buffers = buffers; *threshold_buffers = buffers * DM_BUFIO_WRITEBACK_PERCENT / 100; } /* * Check if we're over watermark. * If we are over threshold_buffers, start freeing buffers. * If we're over "limit_buffers", block until we get under the limit. */ static void __check_watermark(struct dm_bufio_client *c) { unsigned long threshold_buffers, limit_buffers; __get_memory_limit(c, &threshold_buffers, &limit_buffers); while (c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY] > limit_buffers) { struct dm_buffer *b = __get_unclaimed_buffer(c); if (!b) return; __free_buffer_wake(b); dm_bufio_cond_resched(); } if (c->n_buffers[LIST_DIRTY] > threshold_buffers) __write_dirty_buffers_async(c, 1); } /* * Find a buffer in the hash. */ static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block) { struct dm_buffer *b; struct hlist_node *hn; hlist_for_each_entry(b, hn, &c->cache_hash[DM_BUFIO_HASH(block)], hash_list) { dm_bufio_cond_resched(); if (b->block == block) return b; } return NULL; } /*---------------------------------------------------------------- * Getting a buffer *--------------------------------------------------------------*/ enum new_flag { NF_FRESH = 0, NF_READ = 1, NF_GET = 2 }; static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block, enum new_flag nf, struct dm_buffer **bp, int *need_submit) { struct dm_buffer *b, *new_b = NULL; *need_submit = 0; b = __find(c, block); if (b) { b->hold_count++; __relink_lru(b, test_bit(B_DIRTY, &b->state) || test_bit(B_WRITING, &b->state)); return b; } if (nf == NF_GET) return NULL; new_b = __alloc_buffer_wait(c); /* * We've had a period where the mutex was unlocked, so need to * recheck the hash table. */ b = __find(c, block); if (b) { __free_buffer_wake(new_b); b->hold_count++; __relink_lru(b, test_bit(B_DIRTY, &b->state) || test_bit(B_WRITING, &b->state)); return b; } __check_watermark(c); b = new_b; b->hold_count = 1; b->read_error = 0; b->write_error = 0; __link_buffer(b, block, LIST_CLEAN); if (nf == NF_FRESH) { b->state = 0; return b; } b->state = 1 << B_READING; *need_submit = 1; return b; } /* * The endio routine for reading: set the error, clear the bit and wake up * anyone waiting on the buffer. */ static void read_endio(struct bio *bio, int error) { struct dm_buffer *b = container_of(bio, struct dm_buffer, bio); b->read_error = error; BUG_ON(!test_bit(B_READING, &b->state)); smp_mb__before_clear_bit(); clear_bit(B_READING, &b->state); smp_mb__after_clear_bit(); wake_up_bit(&b->state, B_READING); } /* * A common routine for dm_bufio_new and dm_bufio_read. Operation of these * functions is similar except that dm_bufio_new doesn't read the * buffer from the disk (assuming that the caller overwrites all the data * and uses dm_bufio_mark_buffer_dirty to write new data back). */ static void *new_read(struct dm_bufio_client *c, sector_t block, enum new_flag nf, struct dm_buffer **bp) { int need_submit; struct dm_buffer *b; dm_bufio_lock(c); b = __bufio_new(c, block, nf, bp, &need_submit); dm_bufio_unlock(c); if (!b || IS_ERR(b)) return b; if (need_submit) submit_io(b, READ, b->block, read_endio); wait_on_bit(&b->state, B_READING, do_io_schedule, TASK_UNINTERRUPTIBLE); if (b->read_error) { int error = b->read_error; dm_bufio_release(b); return ERR_PTR(error); } *bp = b; return b->data; } void *dm_bufio_get(struct dm_bufio_client *c, sector_t block, struct dm_buffer **bp) { return new_read(c, block, NF_GET, bp); } EXPORT_SYMBOL_GPL(dm_bufio_get); void *dm_bufio_read(struct dm_bufio_client *c, sector_t block, struct dm_buffer **bp) { BUG_ON(dm_bufio_in_request()); return new_read(c, block, NF_READ, bp); } EXPORT_SYMBOL_GPL(dm_bufio_read); void *dm_bufio_new(struct dm_bufio_client *c, sector_t block, struct dm_buffer **bp) { BUG_ON(dm_bufio_in_request()); return new_read(c, block, NF_FRESH, bp); } EXPORT_SYMBOL_GPL(dm_bufio_new); void dm_bufio_release(struct dm_buffer *b) { struct dm_bufio_client *c = b->c; dm_bufio_lock(c); BUG_ON(test_bit(B_READING, &b->state)); BUG_ON(!b->hold_count); b->hold_count--; if (!b->hold_count) { wake_up(&c->free_buffer_wait); /* * If there were errors on the buffer, and the buffer is not * to be written, free the buffer. There is no point in caching * invalid buffer. */ if ((b->read_error || b->write_error) && !test_bit(B_WRITING, &b->state) && !test_bit(B_DIRTY, &b->state)) { __unlink_buffer(b); __free_buffer_wake(b); } } dm_bufio_unlock(c); } EXPORT_SYMBOL_GPL(dm_bufio_release); void dm_bufio_mark_buffer_dirty(struct dm_buffer *b) { struct dm_bufio_client *c = b->c; dm_bufio_lock(c); if (!test_and_set_bit(B_DIRTY, &b->state)) __relink_lru(b, LIST_DIRTY); dm_bufio_unlock(c); } EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty); void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c) { BUG_ON(dm_bufio_in_request()); dm_bufio_lock(c); __write_dirty_buffers_async(c, 0); dm_bufio_unlock(c); } EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async); /* * For performance, it is essential that the buffers are written asynchronously * and simultaneously (so that the block layer can merge the writes) and then * waited upon. * * Finally, we flush hardware disk cache. */ int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c) { int a, f; unsigned long buffers_processed = 0; struct dm_buffer *b, *tmp; dm_bufio_lock(c); __write_dirty_buffers_async(c, 0); again: list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) { int dropped_lock = 0; if (buffers_processed < c->n_buffers[LIST_DIRTY]) buffers_processed++; BUG_ON(test_bit(B_READING, &b->state)); if (test_bit(B_WRITING, &b->state)) { if (buffers_processed < c->n_buffers[LIST_DIRTY]) { dropped_lock = 1; b->hold_count++; dm_bufio_unlock(c); wait_on_bit(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE); dm_bufio_lock(c); b->hold_count--; } else wait_on_bit(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE); } if (!test_bit(B_DIRTY, &b->state) && !test_bit(B_WRITING, &b->state)) __relink_lru(b, LIST_CLEAN); dm_bufio_cond_resched(); /* * If we dropped the lock, the list is no longer consistent, * so we must restart the search. * * In the most common case, the buffer just processed is * relinked to the clean list, so we won't loop scanning the * same buffer again and again. * * This may livelock if there is another thread simultaneously * dirtying buffers, so we count the number of buffers walked * and if it exceeds the total number of buffers, it means that * someone is doing some writes simultaneously with us. In * this case, stop, dropping the lock. */ if (dropped_lock) goto again; } wake_up(&c->free_buffer_wait); dm_bufio_unlock(c); a = xchg(&c->async_write_error, 0); f = dm_bufio_issue_flush(c); if (a) return a; return f; } EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers); /* * Use dm-io to send and empty barrier flush the device. */ int dm_bufio_issue_flush(struct dm_bufio_client *c) { struct dm_io_request io_req = { .bi_rw = REQ_FLUSH, .mem.type = DM_IO_KMEM, .mem.ptr.addr = NULL, .client = c->dm_io, }; struct dm_io_region io_reg = { .bdev = c->bdev, .sector = 0, .count = 0, }; BUG_ON(dm_bufio_in_request()); return dm_io(&io_req, 1, &io_reg, NULL); } EXPORT_SYMBOL_GPL(dm_bufio_issue_flush); /* * We first delete any other buffer that may be at that new location. * * Then, we write the buffer to the original location if it was dirty. * * Then, if we are the only one who is holding the buffer, relink the buffer * in the hash queue for the new location. * * If there was someone else holding the buffer, we write it to the new * location but not relink it, because that other user needs to have the buffer * at the same place. */ void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block) { struct dm_bufio_client *c = b->c; struct dm_buffer *new; BUG_ON(dm_bufio_in_request()); dm_bufio_lock(c); retry: new = __find(c, new_block); if (new) { if (new->hold_count) { __wait_for_free_buffer(c); goto retry; } /* * FIXME: Is there any point waiting for a write that's going * to be overwritten in a bit? */ __make_buffer_clean(new); __unlink_buffer(new); __free_buffer_wake(new); } BUG_ON(!b->hold_count); BUG_ON(test_bit(B_READING, &b->state)); __write_dirty_buffer(b); if (b->hold_count == 1) { wait_on_bit(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE); set_bit(B_DIRTY, &b->state); __unlink_buffer(b); __link_buffer(b, new_block, LIST_DIRTY); } else { sector_t old_block; wait_on_bit_lock(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE); /* * Relink buffer to "new_block" so that write_callback * sees "new_block" as a block number. * After the write, link the buffer back to old_block. * All this must be done in bufio lock, so that block number * change isn't visible to other threads. */ old_block = b->block; __unlink_buffer(b); __link_buffer(b, new_block, b->list_mode); submit_io(b, WRITE, new_block, write_endio); wait_on_bit(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE); __unlink_buffer(b); __link_buffer(b, old_block, b->list_mode); } dm_bufio_unlock(c); dm_bufio_release(b); } EXPORT_SYMBOL_GPL(dm_bufio_release_move); unsigned dm_bufio_get_block_size(struct dm_bufio_client *c) { return c->block_size; } EXPORT_SYMBOL_GPL(dm_bufio_get_block_size); sector_t dm_bufio_get_device_size(struct dm_bufio_client *c) { return i_size_read(c->bdev->bd_inode) >> (SECTOR_SHIFT + c->sectors_per_block_bits); } EXPORT_SYMBOL_GPL(dm_bufio_get_device_size); sector_t dm_bufio_get_block_number(struct dm_buffer *b) { return b->block; } EXPORT_SYMBOL_GPL(dm_bufio_get_block_number); void *dm_bufio_get_block_data(struct dm_buffer *b) { return b->data; } EXPORT_SYMBOL_GPL(dm_bufio_get_block_data); void *dm_bufio_get_aux_data(struct dm_buffer *b) { return b + 1; } EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data); struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b) { return b->c; } EXPORT_SYMBOL_GPL(dm_bufio_get_client); static void drop_buffers(struct dm_bufio_client *c) { struct dm_buffer *b; int i; BUG_ON(dm_bufio_in_request()); /* * An optimization so that the buffers are not written one-by-one. */ dm_bufio_write_dirty_buffers_async(c); dm_bufio_lock(c); while ((b = __get_unclaimed_buffer(c))) __free_buffer_wake(b); for (i = 0; i < LIST_SIZE; i++) list_for_each_entry(b, &c->lru[i], lru_list) DMERR("leaked buffer %llx, hold count %u, list %d", (unsigned long long)b->block, b->hold_count, i); for (i = 0; i < LIST_SIZE; i++) BUG_ON(!list_empty(&c->lru[i])); dm_bufio_unlock(c); } /* * Test if the buffer is unused and too old, and commit it. * At if noio is set, we must not do any I/O because we hold * dm_bufio_clients_lock and we would risk deadlock if the I/O gets rerouted to * different bufio client. */ static int __cleanup_old_buffer(struct dm_buffer *b, gfp_t gfp, unsigned long max_jiffies) { if (jiffies - b->last_accessed < max_jiffies) return 1; if (!(gfp & __GFP_IO)) { if (test_bit(B_READING, &b->state) || test_bit(B_WRITING, &b->state) || test_bit(B_DIRTY, &b->state)) return 1; } if (b->hold_count) return 1; __make_buffer_clean(b); __unlink_buffer(b); __free_buffer_wake(b); return 0; } static void __scan(struct dm_bufio_client *c, unsigned long nr_to_scan, struct shrink_control *sc) { int l; struct dm_buffer *b, *tmp; for (l = 0; l < LIST_SIZE; l++) { list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) if (!__cleanup_old_buffer(b, sc->gfp_mask, 0) && !--nr_to_scan) return; dm_bufio_cond_resched(); } } static int shrink(struct shrinker *shrinker, struct shrink_control *sc) { struct dm_bufio_client *c = container_of(shrinker, struct dm_bufio_client, shrinker); unsigned long r; unsigned long nr_to_scan = sc->nr_to_scan; if (sc->gfp_mask & __GFP_IO) dm_bufio_lock(c); else if (!dm_bufio_trylock(c)) return !nr_to_scan ? 0 : -1; if (nr_to_scan) __scan(c, nr_to_scan, sc); r = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY]; if (r > INT_MAX) r = INT_MAX; dm_bufio_unlock(c); return r; } /* * Create the buffering interface */ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size, unsigned reserved_buffers, unsigned aux_size, void (*alloc_callback)(struct dm_buffer *), void (*write_callback)(struct dm_buffer *)) { int r; struct dm_bufio_client *c; unsigned i; BUG_ON(block_size < 1 << SECTOR_SHIFT || (block_size & (block_size - 1))); c = kmalloc(sizeof(*c), GFP_KERNEL); if (!c) { r = -ENOMEM; goto bad_client; } c->cache_hash = vmalloc(sizeof(struct hlist_head) << DM_BUFIO_HASH_BITS); if (!c->cache_hash) { r = -ENOMEM; goto bad_hash; } c->bdev = bdev; c->block_size = block_size; c->sectors_per_block_bits = ffs(block_size) - 1 - SECTOR_SHIFT; c->pages_per_block_bits = (ffs(block_size) - 1 >= PAGE_SHIFT) ? ffs(block_size) - 1 - PAGE_SHIFT : 0; c->blocks_per_page_bits = (ffs(block_size) - 1 < PAGE_SHIFT ? PAGE_SHIFT - (ffs(block_size) - 1) : 0); c->aux_size = aux_size; c->alloc_callback = alloc_callback; c->write_callback = write_callback; for (i = 0; i < LIST_SIZE; i++) { INIT_LIST_HEAD(&c->lru[i]); c->n_buffers[i] = 0; } for (i = 0; i < 1 << DM_BUFIO_HASH_BITS; i++) INIT_HLIST_HEAD(&c->cache_hash[i]); mutex_init(&c->lock); INIT_LIST_HEAD(&c->reserved_buffers); c->need_reserved_buffers = reserved_buffers; init_waitqueue_head(&c->free_buffer_wait); c->async_write_error = 0; c->dm_io = dm_io_client_create(); if (IS_ERR(c->dm_io)) { r = PTR_ERR(c->dm_io); goto bad_dm_io; } mutex_lock(&dm_bufio_clients_lock); if (c->blocks_per_page_bits) { if (!DM_BUFIO_CACHE_NAME(c)) { DM_BUFIO_CACHE_NAME(c) = kasprintf(GFP_KERNEL, "dm_bufio_cache-%u", c->block_size); if (!DM_BUFIO_CACHE_NAME(c)) { r = -ENOMEM; mutex_unlock(&dm_bufio_clients_lock); goto bad_cache; } } if (!DM_BUFIO_CACHE(c)) { DM_BUFIO_CACHE(c) = kmem_cache_create(DM_BUFIO_CACHE_NAME(c), c->block_size, c->block_size, 0, NULL); if (!DM_BUFIO_CACHE(c)) { r = -ENOMEM; mutex_unlock(&dm_bufio_clients_lock); goto bad_cache; } } } mutex_unlock(&dm_bufio_clients_lock); while (c->need_reserved_buffers) { struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL); if (!b) { r = -ENOMEM; goto bad_buffer; } __free_buffer_wake(b); } mutex_lock(&dm_bufio_clients_lock); dm_bufio_client_count++; list_add(&c->client_list, &dm_bufio_all_clients); __cache_size_refresh(); mutex_unlock(&dm_bufio_clients_lock); c->shrinker.shrink = shrink; c->shrinker.seeks = 1; c->shrinker.batch = 0; register_shrinker(&c->shrinker); return c; bad_buffer: bad_cache: while (!list_empty(&c->reserved_buffers)) { struct dm_buffer *b = list_entry(c->reserved_buffers.next, struct dm_buffer, lru_list); list_del(&b->lru_list); free_buffer(b); } dm_io_client_destroy(c->dm_io); bad_dm_io: vfree(c->cache_hash); bad_hash: kfree(c); bad_client: return ERR_PTR(r); } EXPORT_SYMBOL_GPL(dm_bufio_client_create); /* * Free the buffering interface. * It is required that there are no references on any buffers. */ void dm_bufio_client_destroy(struct dm_bufio_client *c) { unsigned i; drop_buffers(c); unregister_shrinker(&c->shrinker); mutex_lock(&dm_bufio_clients_lock); list_del(&c->client_list); dm_bufio_client_count--; __cache_size_refresh(); mutex_unlock(&dm_bufio_clients_lock); for (i = 0; i < 1 << DM_BUFIO_HASH_BITS; i++) BUG_ON(!hlist_empty(&c->cache_hash[i])); BUG_ON(c->need_reserved_buffers); while (!list_empty(&c->reserved_buffers)) { struct dm_buffer *b = list_entry(c->reserved_buffers.next, struct dm_buffer, lru_list); list_del(&b->lru_list); free_buffer(b); } for (i = 0; i < LIST_SIZE; i++) if (c->n_buffers[i]) DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]); for (i = 0; i < LIST_SIZE; i++) BUG_ON(c->n_buffers[i]); dm_io_client_destroy(c->dm_io); vfree(c->cache_hash); kfree(c); } EXPORT_SYMBOL_GPL(dm_bufio_client_destroy); static void cleanup_old_buffers(void) { unsigned long max_age = dm_bufio_max_age; struct dm_bufio_client *c; barrier(); if (max_age > ULONG_MAX / HZ) max_age = ULONG_MAX / HZ; mutex_lock(&dm_bufio_clients_lock); list_for_each_entry(c, &dm_bufio_all_clients, client_list) { if (!dm_bufio_trylock(c)) continue; while (!list_empty(&c->lru[LIST_CLEAN])) { struct dm_buffer *b; b = list_entry(c->lru[LIST_CLEAN].prev, struct dm_buffer, lru_list); if (__cleanup_old_buffer(b, 0, max_age * HZ)) break; dm_bufio_cond_resched(); } dm_bufio_unlock(c); dm_bufio_cond_resched(); } mutex_unlock(&dm_bufio_clients_lock); } static struct workqueue_struct *dm_bufio_wq; static struct delayed_work dm_bufio_work; static void work_fn(struct work_struct *w) { cleanup_old_buffers(); queue_delayed_work(dm_bufio_wq, &dm_bufio_work, DM_BUFIO_WORK_TIMER_SECS * HZ); } /*---------------------------------------------------------------- * Module setup *--------------------------------------------------------------*/ /* * This is called only once for the whole dm_bufio module. * It initializes memory limit. */ static int __init dm_bufio_init(void) { __u64 mem; memset(&dm_bufio_caches, 0, sizeof dm_bufio_caches); memset(&dm_bufio_cache_names, 0, sizeof dm_bufio_cache_names); mem = (__u64)((totalram_pages - totalhigh_pages) * DM_BUFIO_MEMORY_PERCENT / 100) << PAGE_SHIFT; if (mem > ULONG_MAX) mem = ULONG_MAX; #ifdef CONFIG_MMU /* * Get the size of vmalloc space the same way as VMALLOC_TOTAL * in fs/proc/internal.h */ if (mem > (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100) mem = (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100; #endif dm_bufio_default_cache_size = mem; mutex_lock(&dm_bufio_clients_lock); __cache_size_refresh(); mutex_unlock(&dm_bufio_clients_lock); dm_bufio_wq = create_singlethread_workqueue("dm_bufio_cache"); if (!dm_bufio_wq) return -ENOMEM; INIT_DELAYED_WORK(&dm_bufio_work, work_fn); queue_delayed_work(dm_bufio_wq, &dm_bufio_work, DM_BUFIO_WORK_TIMER_SECS * HZ); return 0; } /* * This is called once when unloading the dm_bufio module. */ static void __exit dm_bufio_exit(void) { int bug = 0; int i; cancel_delayed_work_sync(&dm_bufio_work); destroy_workqueue(dm_bufio_wq); for (i = 0; i < ARRAY_SIZE(dm_bufio_caches); i++) { struct kmem_cache *kc = dm_bufio_caches[i]; if (kc) kmem_cache_destroy(kc); } for (i = 0; i < ARRAY_SIZE(dm_bufio_cache_names); i++) kfree(dm_bufio_cache_names[i]); if (dm_bufio_client_count) { DMCRIT("%s: dm_bufio_client_count leaked: %d", __func__, dm_bufio_client_count); bug = 1; } if (dm_bufio_current_allocated) { DMCRIT("%s: dm_bufio_current_allocated leaked: %lu", __func__, dm_bufio_current_allocated); bug = 1; } if (dm_bufio_allocated_get_free_pages) { DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu", __func__, dm_bufio_allocated_get_free_pages); bug = 1; } if (dm_bufio_allocated_vmalloc) { DMCRIT("%s: dm_bufio_vmalloc leaked: %lu", __func__, dm_bufio_allocated_vmalloc); bug = 1; } if (bug) BUG(); } module_init(dm_bufio_init) module_exit(dm_bufio_exit) module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR); MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache"); module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR); MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds"); module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR); MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory"); module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO); MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc"); module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO); MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages"); module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO); MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc"); module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO); MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache"); MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>"); MODULE_DESCRIPTION(DM_NAME " buffered I/O library"); MODULE_LICENSE("GPL");