diff options
Diffstat (limited to 'drivers/md/dm-bufio.c')
| -rw-r--r-- | drivers/md/dm-bufio.c | 1994 |
1 files changed, 1994 insertions, 0 deletions
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c new file mode 100644 index 000000000..b3b799f84 --- /dev/null +++ b/drivers/md/dm-bufio.c @@ -0,0 +1,1994 @@ +/* + * Copyright (C) 2009-2011 Red Hat, Inc. + * + * Author: Mikulas Patocka <mpatocka@redhat.com> + * + * This file is released under the GPL. + */ + +#include <linux/dm-bufio.h> + +#include <linux/device-mapper.h> +#include <linux/dm-io.h> +#include <linux/slab.h> +#include <linux/sched/mm.h> +#include <linux/jiffies.h> +#include <linux/vmalloc.h> +#include <linux/shrinker.h> +#include <linux/module.h> +#include <linux/rbtree.h> +#include <linux/stacktrace.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 30 + +/* + * Free buffers when they are older than this (seconds) + */ +#define DM_BUFIO_DEFAULT_AGE_SECS 300 + +/* + * The nr of bytes of cached data to keep around. + */ +#define DM_BUFIO_DEFAULT_RETAIN_BYTES (256 * 1024) + +/* + * Align buffer writes to this boundary. + * Tests show that SSDs have the highest IOPS when using 4k writes. + */ +#define DM_BUFIO_WRITE_ALIGN 4096 + +/* + * 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; + s8 sectors_per_block_bits; + void (*alloc_callback)(struct dm_buffer *); + void (*write_callback)(struct dm_buffer *); + + struct kmem_cache *slab_buffer; + struct kmem_cache *slab_cache; + struct dm_io_client *dm_io; + + struct list_head reserved_buffers; + unsigned need_reserved_buffers; + + unsigned minimum_buffers; + + struct rb_root buffer_tree; + wait_queue_head_t free_buffer_wait; + + sector_t start; + + 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 rb_node node; + struct list_head lru_list; + sector_t block; + void *data; + unsigned char data_mode; /* DATA_MODE_* */ + unsigned char list_mode; /* LIST_* */ + blk_status_t read_error; + blk_status_t write_error; + unsigned hold_count; + unsigned long state; + unsigned long last_accessed; + unsigned dirty_start; + unsigned dirty_end; + unsigned write_start; + unsigned write_end; + struct dm_bufio_client *c; + struct list_head write_list; + void (*end_io)(struct dm_buffer *, blk_status_t); +#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING +#define MAX_STACK 10 + struct stack_trace stack_trace; + unsigned long stack_entries[MAX_STACK]; +#endif +}; + +/*----------------------------------------------------------------*/ + +#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); +} + +/*----------------------------------------------------------------*/ + +/* + * 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_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES; + +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); + +#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING +static void buffer_record_stack(struct dm_buffer *b) +{ + b->stack_trace.nr_entries = 0; + b->stack_trace.max_entries = MAX_STACK; + b->stack_trace.entries = b->stack_entries; + b->stack_trace.skip = 2; + save_stack_trace(&b->stack_trace); +} +#endif + +/*---------------------------------------------------------------- + * A red/black tree acts as an index for all the buffers. + *--------------------------------------------------------------*/ +static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block) +{ + struct rb_node *n = c->buffer_tree.rb_node; + struct dm_buffer *b; + + while (n) { + b = container_of(n, struct dm_buffer, node); + + if (b->block == block) + return b; + + n = (b->block < block) ? n->rb_left : n->rb_right; + } + + return NULL; +} + +static void __insert(struct dm_bufio_client *c, struct dm_buffer *b) +{ + struct rb_node **new = &c->buffer_tree.rb_node, *parent = NULL; + struct dm_buffer *found; + + while (*new) { + found = container_of(*new, struct dm_buffer, node); + + if (found->block == b->block) { + BUG_ON(found != b); + return; + } + + parent = *new; + new = (found->block < b->block) ? + &((*new)->rb_left) : &((*new)->rb_right); + } + + rb_link_node(&b->node, parent, new); + rb_insert_color(&b->node, &c->buffer_tree); +} + +static void __remove(struct dm_bufio_client *c, struct dm_buffer *b) +{ + rb_erase(&b->node, &c->buffer_tree); +} + +/*----------------------------------------------------------------*/ + +static void adjust_total_allocated(unsigned char 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 = READ_ONCE(dm_bufio_cache_size); + + /* + * 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, + unsigned char *data_mode) +{ + if (unlikely(c->slab_cache != NULL)) { + *data_mode = DATA_MODE_SLAB; + return kmem_cache_alloc(c->slab_cache, gfp_mask); + } + + if (c->block_size <= KMALLOC_MAX_SIZE && + gfp_mask & __GFP_NORETRY) { + *data_mode = DATA_MODE_GET_FREE_PAGES; + return (void *)__get_free_pages(gfp_mask, + c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT)); + } + + *data_mode = DATA_MODE_VMALLOC; + + /* + * __vmalloc allocates the data pages and auxiliary structures with + * gfp_flags that were specified, but pagetables are always allocated + * with GFP_KERNEL, no matter what was specified as gfp_mask. + * + * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that + * all allocations done by this process (including pagetables) are done + * as if GFP_NOIO was specified. + */ + if (gfp_mask & __GFP_NORETRY) { + unsigned noio_flag = memalloc_noio_save(); + void *ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); + + memalloc_noio_restore(noio_flag); + return ptr; + } + + 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, unsigned char data_mode) +{ + switch (data_mode) { + case DATA_MODE_SLAB: + kmem_cache_free(c->slab_cache, data); + break; + + case DATA_MODE_GET_FREE_PAGES: + free_pages((unsigned long)data, + c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT)); + 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 = kmem_cache_alloc(c->slab_buffer, gfp_mask); + + if (!b) + return NULL; + + b->c = c; + + b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode); + if (!b->data) { + kmem_cache_free(c->slab_buffer, b); + return NULL; + } + + adjust_total_allocated(b->data_mode, (long)c->block_size); + +#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING + memset(&b->stack_trace, 0, sizeof(b->stack_trace)); +#endif + 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); + kmem_cache_free(c->slab_buffer, 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]); + __insert(b->c, b); + 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]--; + __remove(b->c, b); + 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_move(&b->lru_list, &c->lru[dirty]); + b->last_accessed = jiffies; +} + +/*---------------------------------------------------------------- + * 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; + * + * 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->end_io(b, unlikely(error != 0) ? BLK_STS_IOERR : 0); +} + +static void use_dmio(struct dm_buffer *b, int rw, sector_t sector, + unsigned n_sectors, unsigned offset) +{ + int r; + struct dm_io_request io_req = { + .bi_op = rw, + .bi_op_flags = 0, + .notify.fn = dmio_complete, + .notify.context = b, + .client = b->c->dm_io, + }; + struct dm_io_region region = { + .bdev = b->c->bdev, + .sector = sector, + .count = n_sectors, + }; + + if (b->data_mode != DATA_MODE_VMALLOC) { + io_req.mem.type = DM_IO_KMEM; + io_req.mem.ptr.addr = (char *)b->data + offset; + } else { + io_req.mem.type = DM_IO_VMA; + io_req.mem.ptr.vma = (char *)b->data + offset; + } + + r = dm_io(&io_req, 1, ®ion, NULL); + if (unlikely(r)) + b->end_io(b, errno_to_blk_status(r)); +} + +static void bio_complete(struct bio *bio) +{ + struct dm_buffer *b = bio->bi_private; + blk_status_t status = bio->bi_status; + bio_put(bio); + b->end_io(b, status); +} + +static void use_bio(struct dm_buffer *b, int rw, sector_t sector, + unsigned n_sectors, unsigned offset) +{ + struct bio *bio; + char *ptr; + unsigned vec_size, len; + + vec_size = b->c->block_size >> PAGE_SHIFT; + if (unlikely(b->c->sectors_per_block_bits < PAGE_SHIFT - SECTOR_SHIFT)) + vec_size += 2; + + bio = bio_kmalloc(GFP_NOWAIT | __GFP_NORETRY | __GFP_NOWARN, vec_size); + if (!bio) { +dmio: + use_dmio(b, rw, sector, n_sectors, offset); + return; + } + + bio->bi_iter.bi_sector = sector; + bio_set_dev(bio, b->c->bdev); + bio_set_op_attrs(bio, rw, 0); + bio->bi_end_io = bio_complete; + bio->bi_private = b; + + ptr = (char *)b->data + offset; + len = n_sectors << SECTOR_SHIFT; + + do { + unsigned this_step = min((unsigned)(PAGE_SIZE - offset_in_page(ptr)), len); + if (!bio_add_page(bio, virt_to_page(ptr), this_step, + offset_in_page(ptr))) { + bio_put(bio); + goto dmio; + } + + len -= this_step; + ptr += this_step; + } while (len > 0); + + submit_bio(bio); +} + +static void submit_io(struct dm_buffer *b, int rw, void (*end_io)(struct dm_buffer *, blk_status_t)) +{ + unsigned n_sectors; + sector_t sector; + unsigned offset, end; + + b->end_io = end_io; + + if (likely(b->c->sectors_per_block_bits >= 0)) + sector = b->block << b->c->sectors_per_block_bits; + else + sector = b->block * (b->c->block_size >> SECTOR_SHIFT); + sector += b->c->start; + + if (rw != REQ_OP_WRITE) { + n_sectors = b->c->block_size >> SECTOR_SHIFT; + offset = 0; + } else { + if (b->c->write_callback) + b->c->write_callback(b); + offset = b->write_start; + end = b->write_end; + offset &= -DM_BUFIO_WRITE_ALIGN; + end += DM_BUFIO_WRITE_ALIGN - 1; + end &= -DM_BUFIO_WRITE_ALIGN; + if (unlikely(end > b->c->block_size)) + end = b->c->block_size; + + sector += offset >> SECTOR_SHIFT; + n_sectors = (end - offset) >> SECTOR_SHIFT; + } + + if (b->data_mode != DATA_MODE_VMALLOC) + use_bio(b, rw, sector, n_sectors, offset); + else + use_dmio(b, rw, sector, n_sectors, offset); +} + +/*---------------------------------------------------------------- + * 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 dm_buffer *b, blk_status_t status) +{ + b->write_error = status; + if (unlikely(status)) { + struct dm_bufio_client *c = b->c; + + (void)cmpxchg(&c->async_write_error, 0, + blk_status_to_errno(status)); + } + + BUG_ON(!test_bit(B_WRITING, &b->state)); + + smp_mb__before_atomic(); + clear_bit(B_WRITING, &b->state); + smp_mb__after_atomic(); + + wake_up_bit(&b->state, B_WRITING); +} + +/* + * 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, + struct list_head *write_list) +{ + if (!test_bit(B_DIRTY, &b->state)) + return; + + clear_bit(B_DIRTY, &b->state); + wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE); + + b->write_start = b->dirty_start; + b->write_end = b->dirty_end; + + if (!write_list) + submit_io(b, REQ_OP_WRITE, write_endio); + else + list_add_tail(&b->write_list, write_list); +} + +static void __flush_write_list(struct list_head *write_list) +{ + struct blk_plug plug; + blk_start_plug(&plug); + while (!list_empty(write_list)) { + struct dm_buffer *b = + list_entry(write_list->next, struct dm_buffer, write_list); + list_del(&b->write_list); + submit_io(b, REQ_OP_WRITE, write_endio); + cond_resched(); + } + blk_finish_plug(&plug); +} + +/* + * 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_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE); + __write_dirty_buffer(b, NULL); + wait_on_bit_io(&b->state, B_WRITING, 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; + } + 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; + } + 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_current_state(TASK_UNINTERRUPTIBLE); + dm_bufio_unlock(c); + + io_schedule(); + + remove_wait_queue(&c->free_buffer_wait, &wait); + + dm_bufio_lock(c); +} + +enum new_flag { + NF_FRESH = 0, + NF_READ = 1, + NF_GET = 2, + NF_PREFETCH = 3 +}; + +/* + * 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, enum new_flag nf) +{ + struct dm_buffer *b; + bool tried_noio_alloc = false; + + /* + * 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_NOWAIT: don't wait; if we need to sleep we'll release our + * mutex and wait ourselves. + * __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_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); + if (b) + return b; + } + + if (nf == NF_PREFETCH) + return NULL; + + if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) { + dm_bufio_unlock(c); + b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); + dm_bufio_lock(c); + if (b) + return b; + tried_noio_alloc = true; + } + + 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, enum new_flag nf) +{ + struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf); + + if (!b) + return NULL; + + 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 list_head *write_list) +{ + 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, write_list); + 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 (unlikely(READ_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch)) { + if (mutex_trylock(&dm_bufio_clients_lock)) { + __cache_size_refresh(); + mutex_unlock(&dm_bufio_clients_lock); + } + } + + buffers = dm_bufio_cache_size_per_client; + if (likely(c->sectors_per_block_bits >= 0)) + buffers >>= c->sectors_per_block_bits + SECTOR_SHIFT; + else + buffers /= c->block_size; + + if (buffers < c->minimum_buffers) + buffers = c->minimum_buffers; + + *limit_buffers = buffers; + *threshold_buffers = mult_frac(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, + struct list_head *write_list) +{ + 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); + cond_resched(); + } + + if (c->n_buffers[LIST_DIRTY] > threshold_buffers) + __write_dirty_buffers_async(c, 1, write_list); +} + +/*---------------------------------------------------------------- + * Getting a buffer + *--------------------------------------------------------------*/ + +static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block, + enum new_flag nf, int *need_submit, + struct list_head *write_list) +{ + struct dm_buffer *b, *new_b = NULL; + + *need_submit = 0; + + b = __find(c, block); + if (b) + goto found_buffer; + + if (nf == NF_GET) + return NULL; + + new_b = __alloc_buffer_wait(c, nf); + if (!new_b) + return NULL; + + /* + * 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); + goto found_buffer; + } + + __check_watermark(c, write_list); + + 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; + +found_buffer: + if (nf == NF_PREFETCH) + return NULL; + /* + * Note: it is essential that we don't wait for the buffer to be + * read if dm_bufio_get function is used. Both dm_bufio_get and + * dm_bufio_prefetch can be used in the driver request routine. + * If the user called both dm_bufio_prefetch and dm_bufio_get on + * the same buffer, it would deadlock if we waited. + */ + if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state))) + return NULL; + + b->hold_count++; + __relink_lru(b, test_bit(B_DIRTY, &b->state) || + test_bit(B_WRITING, &b->state)); + 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 dm_buffer *b, blk_status_t status) +{ + b->read_error = status; + + BUG_ON(!test_bit(B_READING, &b->state)); + + smp_mb__before_atomic(); + clear_bit(B_READING, &b->state); + smp_mb__after_atomic(); + + 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; + + LIST_HEAD(write_list); + + dm_bufio_lock(c); + b = __bufio_new(c, block, nf, &need_submit, &write_list); +#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING + if (b && b->hold_count == 1) + buffer_record_stack(b); +#endif + dm_bufio_unlock(c); + + __flush_write_list(&write_list); + + if (!b) + return NULL; + + if (need_submit) + submit_io(b, REQ_OP_READ, read_endio); + + wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE); + + if (b->read_error) { + int error = blk_status_to_errno(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_prefetch(struct dm_bufio_client *c, + sector_t block, unsigned n_blocks) +{ + struct blk_plug plug; + + LIST_HEAD(write_list); + + BUG_ON(dm_bufio_in_request()); + + blk_start_plug(&plug); + dm_bufio_lock(c); + + for (; n_blocks--; block++) { + int need_submit; + struct dm_buffer *b; + b = __bufio_new(c, block, NF_PREFETCH, &need_submit, + &write_list); + if (unlikely(!list_empty(&write_list))) { + dm_bufio_unlock(c); + blk_finish_plug(&plug); + __flush_write_list(&write_list); + blk_start_plug(&plug); + dm_bufio_lock(c); + } + if (unlikely(b != NULL)) { + dm_bufio_unlock(c); + + if (need_submit) + submit_io(b, REQ_OP_READ, read_endio); + dm_bufio_release(b); + + cond_resched(); + + if (!n_blocks) + goto flush_plug; + dm_bufio_lock(c); + } + } + + dm_bufio_unlock(c); + +flush_plug: + blk_finish_plug(&plug); +} +EXPORT_SYMBOL_GPL(dm_bufio_prefetch); + +void dm_bufio_release(struct dm_buffer *b) +{ + struct dm_bufio_client *c = b->c; + + dm_bufio_lock(c); + + 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_READING, &b->state) && + !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_partial_buffer_dirty(struct dm_buffer *b, + unsigned start, unsigned end) +{ + struct dm_bufio_client *c = b->c; + + BUG_ON(start >= end); + BUG_ON(end > b->c->block_size); + + dm_bufio_lock(c); + + BUG_ON(test_bit(B_READING, &b->state)); + + if (!test_and_set_bit(B_DIRTY, &b->state)) { + b->dirty_start = start; + b->dirty_end = end; + __relink_lru(b, LIST_DIRTY); + } else { + if (start < b->dirty_start) + b->dirty_start = start; + if (end > b->dirty_end) + b->dirty_end = end; + } + + dm_bufio_unlock(c); +} +EXPORT_SYMBOL_GPL(dm_bufio_mark_partial_buffer_dirty); + +void dm_bufio_mark_buffer_dirty(struct dm_buffer *b) +{ + dm_bufio_mark_partial_buffer_dirty(b, 0, b->c->block_size); +} +EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty); + +void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c) +{ + LIST_HEAD(write_list); + + BUG_ON(dm_bufio_in_request()); + + dm_bufio_lock(c); + __write_dirty_buffers_async(c, 0, &write_list); + dm_bufio_unlock(c); + __flush_write_list(&write_list); +} +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; + + LIST_HEAD(write_list); + + dm_bufio_lock(c); + __write_dirty_buffers_async(c, 0, &write_list); + dm_bufio_unlock(c); + __flush_write_list(&write_list); + dm_bufio_lock(c); + +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_io(&b->state, B_WRITING, + TASK_UNINTERRUPTIBLE); + dm_bufio_lock(c); + b->hold_count--; + } else + wait_on_bit_io(&b->state, B_WRITING, + TASK_UNINTERRUPTIBLE); + } + + if (!test_bit(B_DIRTY, &b->state) && + !test_bit(B_WRITING, &b->state)) + __relink_lru(b, LIST_CLEAN); + + 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_op = REQ_OP_WRITE, + .bi_op_flags = REQ_PREFLUSH | REQ_SYNC, + .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, NULL); + if (b->hold_count == 1) { + wait_on_bit_io(&b->state, B_WRITING, + TASK_UNINTERRUPTIBLE); + set_bit(B_DIRTY, &b->state); + b->dirty_start = 0; + b->dirty_end = c->block_size; + __unlink_buffer(b); + __link_buffer(b, new_block, LIST_DIRTY); + } else { + sector_t old_block; + wait_on_bit_lock_io(&b->state, B_WRITING, + 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, REQ_OP_WRITE, write_endio); + wait_on_bit_io(&b->state, B_WRITING, + 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); + +/* + * Free the given buffer. + * + * This is just a hint, if the buffer is in use or dirty, this function + * does nothing. + */ +void dm_bufio_forget(struct dm_bufio_client *c, sector_t block) +{ + struct dm_buffer *b; + + dm_bufio_lock(c); + + b = __find(c, block); + if (b && likely(!b->hold_count) && likely(!b->state)) { + __unlink_buffer(b); + __free_buffer_wake(b); + } + + dm_bufio_unlock(c); +} +EXPORT_SYMBOL_GPL(dm_bufio_forget); + +void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n) +{ + c->minimum_buffers = n; +} +EXPORT_SYMBOL_GPL(dm_bufio_set_minimum_buffers); + +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) +{ + sector_t s = i_size_read(c->bdev->bd_inode) >> SECTOR_SHIFT; + if (s >= c->start) + s -= c->start; + else + s = 0; + if (likely(c->sectors_per_block_bits >= 0)) + s >>= c->sectors_per_block_bits; + else + sector_div(s, c->block_size >> SECTOR_SHIFT); + return s; +} +EXPORT_SYMBOL_GPL(dm_bufio_get_device_size); + +struct dm_io_client *dm_bufio_get_dm_io_client(struct dm_bufio_client *c) +{ + return c->dm_io; +} +EXPORT_SYMBOL_GPL(dm_bufio_get_dm_io_client); + +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; + bool warned = false; + + 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) { + WARN_ON(!warned); + warned = true; + DMERR("leaked buffer %llx, hold count %u, list %d", + (unsigned long long)b->block, b->hold_count, i); +#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING + print_stack_trace(&b->stack_trace, 1); + b->hold_count = 0; /* mark unclaimed to avoid BUG_ON below */ +#endif + } + +#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING + while ((b = __get_unclaimed_buffer(c))) + __free_buffer_wake(b); +#endif + + for (i = 0; i < LIST_SIZE; i++) + BUG_ON(!list_empty(&c->lru[i])); + + dm_bufio_unlock(c); +} + +/* + * We may not be able to evict this buffer if IO pending or the client + * is still using it. Caller is expected to know buffer is too old. + * + * And if GFP_NOFS is used, 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 bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp) +{ + if (!(gfp & __GFP_FS)) { + if (test_bit(B_READING, &b->state) || + test_bit(B_WRITING, &b->state) || + test_bit(B_DIRTY, &b->state)) + return false; + } + + if (b->hold_count) + return false; + + __make_buffer_clean(b); + __unlink_buffer(b); + __free_buffer_wake(b); + + return true; +} + +static unsigned long get_retain_buffers(struct dm_bufio_client *c) +{ + unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes); + if (likely(c->sectors_per_block_bits >= 0)) + retain_bytes >>= c->sectors_per_block_bits + SECTOR_SHIFT; + else + retain_bytes /= c->block_size; + return retain_bytes; +} + +static unsigned long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan, + gfp_t gfp_mask) +{ + int l; + struct dm_buffer *b, *tmp; + unsigned long freed = 0; + unsigned long count = c->n_buffers[LIST_CLEAN] + + c->n_buffers[LIST_DIRTY]; + unsigned long retain_target = get_retain_buffers(c); + + for (l = 0; l < LIST_SIZE; l++) { + list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) { + if (__try_evict_buffer(b, gfp_mask)) + freed++; + if (!--nr_to_scan || ((count - freed) <= retain_target)) + return freed; + cond_resched(); + } + } + return freed; +} + +static unsigned long +dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) +{ + struct dm_bufio_client *c; + unsigned long freed; + + c = container_of(shrink, struct dm_bufio_client, shrinker); + if (sc->gfp_mask & __GFP_FS) + dm_bufio_lock(c); + else if (!dm_bufio_trylock(c)) + return SHRINK_STOP; + + freed = __scan(c, sc->nr_to_scan, sc->gfp_mask); + dm_bufio_unlock(c); + return freed; +} + +static unsigned long +dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc) +{ + struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker); + unsigned long count = READ_ONCE(c->n_buffers[LIST_CLEAN]) + + READ_ONCE(c->n_buffers[LIST_DIRTY]); + unsigned long retain_target = get_retain_buffers(c); + + return (count < retain_target) ? 0 : (count - retain_target); +} + +/* + * 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; + char slab_name[27]; + + if (!block_size || block_size & ((1 << SECTOR_SHIFT) - 1)) { + DMERR("%s: block size not specified or is not multiple of 512b", __func__); + r = -EINVAL; + goto bad_client; + } + + c = kzalloc(sizeof(*c), GFP_KERNEL); + if (!c) { + r = -ENOMEM; + goto bad_client; + } + c->buffer_tree = RB_ROOT; + + c->bdev = bdev; + c->block_size = block_size; + if (is_power_of_2(block_size)) + c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT; + else + c->sectors_per_block_bits = -1; + + 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; + } + + mutex_init(&c->lock); + INIT_LIST_HEAD(&c->reserved_buffers); + c->need_reserved_buffers = reserved_buffers; + + dm_bufio_set_minimum_buffers(c, DM_BUFIO_MIN_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; + } + + if (block_size <= KMALLOC_MAX_SIZE && + (block_size < PAGE_SIZE || !is_power_of_2(block_size))) { + unsigned align = min(1U << __ffs(block_size), (unsigned)PAGE_SIZE); + snprintf(slab_name, sizeof slab_name, "dm_bufio_cache-%u", block_size); + c->slab_cache = kmem_cache_create(slab_name, block_size, align, + SLAB_RECLAIM_ACCOUNT, NULL); + if (!c->slab_cache) { + r = -ENOMEM; + goto bad; + } + } + if (aux_size) + snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer-%u", aux_size); + else + snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer"); + c->slab_buffer = kmem_cache_create(slab_name, sizeof(struct dm_buffer) + aux_size, + 0, SLAB_RECLAIM_ACCOUNT, NULL); + if (!c->slab_buffer) { + r = -ENOMEM; + goto bad; + } + + while (c->need_reserved_buffers) { + struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL); + + if (!b) { + r = -ENOMEM; + goto bad; + } + __free_buffer_wake(b); + } + + c->shrinker.count_objects = dm_bufio_shrink_count; + c->shrinker.scan_objects = dm_bufio_shrink_scan; + c->shrinker.seeks = 1; + c->shrinker.batch = 0; + r = register_shrinker(&c->shrinker); + if (r) + goto bad; + + 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); + + return c; + +bad: + 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); + } + kmem_cache_destroy(c->slab_cache); + kmem_cache_destroy(c->slab_buffer); + dm_io_client_destroy(c->dm_io); +bad_dm_io: + mutex_destroy(&c->lock); + 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); + + BUG_ON(!RB_EMPTY_ROOT(&c->buffer_tree)); + 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]); + + kmem_cache_destroy(c->slab_cache); + kmem_cache_destroy(c->slab_buffer); + dm_io_client_destroy(c->dm_io); + mutex_destroy(&c->lock); + kfree(c); +} +EXPORT_SYMBOL_GPL(dm_bufio_client_destroy); + +void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start) +{ + c->start = start; +} +EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset); + +static unsigned get_max_age_hz(void) +{ + unsigned max_age = READ_ONCE(dm_bufio_max_age); + + if (max_age > UINT_MAX / HZ) + max_age = UINT_MAX / HZ; + + return max_age * HZ; +} + +static bool older_than(struct dm_buffer *b, unsigned long age_hz) +{ + return time_after_eq(jiffies, b->last_accessed + age_hz); +} + +static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz) +{ + struct dm_buffer *b, *tmp; + unsigned long retain_target = get_retain_buffers(c); + unsigned long count; + LIST_HEAD(write_list); + + dm_bufio_lock(c); + + __check_watermark(c, &write_list); + if (unlikely(!list_empty(&write_list))) { + dm_bufio_unlock(c); + __flush_write_list(&write_list); + dm_bufio_lock(c); + } + + count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY]; + list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) { + if (count <= retain_target) + break; + + if (!older_than(b, age_hz)) + break; + + if (__try_evict_buffer(b, 0)) + count--; + + cond_resched(); + } + + dm_bufio_unlock(c); +} + +static void cleanup_old_buffers(void) +{ + unsigned long max_age_hz = get_max_age_hz(); + struct dm_bufio_client *c; + + mutex_lock(&dm_bufio_clients_lock); + + __cache_size_refresh(); + + list_for_each_entry(c, &dm_bufio_all_clients, client_list) + __evict_old_buffers(c, max_age_hz); + + 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; + + dm_bufio_allocated_kmem_cache = 0; + dm_bufio_allocated_get_free_pages = 0; + dm_bufio_allocated_vmalloc = 0; + dm_bufio_current_allocated = 0; + + mem = (__u64)mult_frac(totalram_pages - totalhigh_pages, + DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT; + + if (mem > ULONG_MAX) + mem = ULONG_MAX; + +#ifdef CONFIG_MMU + if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100)) + mem = mult_frac(VMALLOC_TOTAL, 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 = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0); + 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; + + cancel_delayed_work_sync(&dm_bufio_work); + destroy_workqueue(dm_bufio_wq); + + 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; + } + + BUG_ON(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(retain_bytes, dm_bufio_retain_bytes, ulong, S_IRUGO | S_IWUSR); +MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory"); + +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"); |