dm: add bufio
The dm-bufio interface allows you to do cached I/O on devices,
holding recently-read blocks in memory and performing delayed writes.
We don't use buffer cache or page cache already present in the kernel, because:
* we need to handle block sizes larger than a page
* we can't allocate memory to perform reads or we'd have deadlocks
Currently, when a cache is required, we limit its size to a fraction of
available memory. Usage can be viewed and changed in
/sys/module/dm_bufio/parameters/ .
The first user is thin provisioning, but more dm users are planned.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index f75a66e..b1a9214 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -208,6 +208,14 @@
If unsure, say N.
+config DM_BUFIO
+ tristate
+ depends on BLK_DEV_DM && EXPERIMENTAL
+ ---help---
+ This interface allows you to do buffered I/O on a device and acts
+ as a cache, holding recently-read blocks in memory and performing
+ delayed writes.
+
config DM_CRYPT
tristate "Crypt target support"
depends on BLK_DEV_DM
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 448838b..56661c4 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -27,6 +27,7 @@
obj-$(CONFIG_MD_FAULTY) += faulty.o
obj-$(CONFIG_BLK_DEV_MD) += md-mod.o
obj-$(CONFIG_BLK_DEV_DM) += dm-mod.o
+obj-$(CONFIG_DM_BUFIO) += dm-bufio.o
obj-$(CONFIG_DM_CRYPT) += dm-crypt.o
obj-$(CONFIG_DM_DELAY) += dm-delay.o
obj-$(CONFIG_DM_FLAKEY) += dm-flakey.o
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
new file mode 100644
index 0000000..cb24666
--- /dev/null
+++ b/drivers/md/dm-bufio.c
@@ -0,0 +1,1699 @@
+/*
+ * 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>
+
+#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");
diff --git a/drivers/md/dm-bufio.h b/drivers/md/dm-bufio.h
new file mode 100644
index 0000000..5c4c3a0
--- /dev/null
+++ b/drivers/md/dm-bufio.h
@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2009-2011 Red Hat, Inc.
+ *
+ * Author: Mikulas Patocka <mpatocka@redhat.com>
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_BUFIO_H
+#define DM_BUFIO_H
+
+#include <linux/blkdev.h>
+#include <linux/types.h>
+
+/*----------------------------------------------------------------*/
+
+struct dm_bufio_client;
+struct dm_buffer;
+
+/*
+ * Create a buffered IO cache on a given device
+ */
+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 *));
+
+/*
+ * Release a buffered IO cache.
+ */
+void dm_bufio_client_destroy(struct dm_bufio_client *c);
+
+/*
+ * WARNING: to avoid deadlocks, these conditions are observed:
+ *
+ * - At most one thread can hold at most "reserved_buffers" simultaneously.
+ * - Each other threads can hold at most one buffer.
+ * - Threads which call only dm_bufio_get can hold unlimited number of
+ * buffers.
+ */
+
+/*
+ * Read a given block from disk. Returns pointer to data. Returns a
+ * pointer to dm_buffer that can be used to release the buffer or to make
+ * it dirty.
+ */
+void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
+ struct dm_buffer **bp);
+
+/*
+ * Like dm_bufio_read, but return buffer from cache, don't read
+ * it. If the buffer is not in the cache, return NULL.
+ */
+void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
+ struct dm_buffer **bp);
+
+/*
+ * Like dm_bufio_read, but don't read anything from the disk. It is
+ * expected that the caller initializes the buffer and marks it dirty.
+ */
+void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
+ struct dm_buffer **bp);
+
+/*
+ * Release a reference obtained with dm_bufio_{read,get,new}. The data
+ * pointer and dm_buffer pointer is no longer valid after this call.
+ */
+void dm_bufio_release(struct dm_buffer *b);
+
+/*
+ * Mark a buffer dirty. It should be called after the buffer is modified.
+ *
+ * In case of memory pressure, the buffer may be written after
+ * dm_bufio_mark_buffer_dirty, but before dm_bufio_write_dirty_buffers. So
+ * dm_bufio_write_dirty_buffers guarantees that the buffer is on-disk but
+ * the actual writing may occur earlier.
+ */
+void dm_bufio_mark_buffer_dirty(struct dm_buffer *b);
+
+/*
+ * Initiate writing of dirty buffers, without waiting for completion.
+ */
+void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c);
+
+/*
+ * Write all dirty buffers. Guarantees that all dirty buffers created prior
+ * to this call are on disk when this call exits.
+ */
+int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c);
+
+/*
+ * Send an empty write barrier to the device to flush hardware disk cache.
+ */
+int dm_bufio_issue_flush(struct dm_bufio_client *c);
+
+/*
+ * Like dm_bufio_release but also move the buffer to the new
+ * block. dm_bufio_write_dirty_buffers is needed to commit the new block.
+ */
+void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block);
+
+unsigned dm_bufio_get_block_size(struct dm_bufio_client *c);
+sector_t dm_bufio_get_device_size(struct dm_bufio_client *c);
+sector_t dm_bufio_get_block_number(struct dm_buffer *b);
+void *dm_bufio_get_block_data(struct dm_buffer *b);
+void *dm_bufio_get_aux_data(struct dm_buffer *b);
+struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b);
+
+/*----------------------------------------------------------------*/
+
+#endif