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linux-next/drivers/md/dm-bufio.c
Joe Thornber 33096a7822 dm bufio: evict buffers that are past the max age but retain some buffers
These changes help keep metadata backed by dm-bufio in-core longer which
fixes reports of metadata churn in the face of heavy random IO workloads.

Before, bufio evicted all buffers older than DM_BUFIO_DEFAULT_AGE_SECS.
Having a device (e.g. dm-thinp or dm-cache) lose all metadata just
because associated buffers had been idle for some time is unfriendly.

Now, the user may now configure the number of bytes that bufio retains
using the 'retain_bytes' module parameter.  The default is 256K.

Also, the DM_BUFIO_WORK_TIMER_SECS and DM_BUFIO_DEFAULT_AGE_SECS
defaults were quite low so increase them (to 30 and 300 respectively).

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2014-11-10 15:25:26 -05:00

1908 lines
46 KiB
C

/*
* 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/shrinker.h>
#include <linux/module.h>
#include <linux/rbtree.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)
/*
* 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
/*
* 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;
unsigned minimum_buffers;
struct rb_root buffer_tree;
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 rb_node node;
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 list_head write_list;
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 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);
/*----------------------------------------------------------------
* 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(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(&param_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(&param_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 = ACCESS_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,
enum data_mode *data_mode)
{
unsigned noio_flag;
void *ptr;
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;
/*
* __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)
noio_flag = memalloc_noio_save();
ptr = __vmalloc(c->block_size, gfp_mask | __GFP_HIGHMEM, PAGE_KERNEL);
if (gfp_mask & __GFP_NORETRY)
memalloc_noio_restore(noio_flag);
return ptr;
}
/*
* 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]);
__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;
*
* 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, &region, 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_iter.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 (unlikely(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_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);
if (!write_list)
submit_io(b, WRITE, b->block, 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, WRITE, b->block, write_endio);
dm_bufio_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;
}
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);
}
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;
/*
* 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 (nf == NF_PREFETCH)
return NULL;
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);
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 (ACCESS_ONCE(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 < c->minimum_buffers)
buffers = c->minimum_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,
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);
dm_bufio_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 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_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);
dm_bufio_unlock(c);
__flush_write_list(&write_list);
if (!b)
return b;
if (need_submit)
submit_io(b, READ, b->block, read_endio);
wait_on_bit_io(&b->state, B_READING, 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_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, READ, b->block, read_endio);
dm_bufio_release(b);
dm_bufio_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_buffer_dirty(struct dm_buffer *b)
{
struct dm_bufio_client *c = b->c;
dm_bufio_lock(c);
BUG_ON(test_bit(B_READING, &b->state));
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)
{
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);
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 = WRITE_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, NULL);
if (b->hold_count == 1) {
wait_on_bit_io(&b->state, B_WRITING,
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_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, WRITE, new_block, 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(dm_bufio_forget);
void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n)
{
c->minimum_buffers = n;
}
EXPORT_SYMBOL(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)
{
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);
}
/*
* 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 get_retain_buffers(struct dm_bufio_client *c)
{
unsigned retain_bytes = ACCESS_ONCE(dm_bufio_retain_bytes);
return retain_bytes / c->block_size;
}
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 = nr_to_scan;
unsigned 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;
dm_bufio_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;
unsigned long count;
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 0;
count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
dm_bufio_unlock(c);
return count;
}
/*
* 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 = 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;
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;
}
mutex_init(&c->lock);
INIT_LIST_HEAD(&c->reserved_buffers);
c->need_reserved_buffers = reserved_buffers;
c->minimum_buffers = 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;
}
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.count_objects = dm_bufio_shrink_count;
c->shrinker.scan_objects = dm_bufio_shrink_scan;
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:
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]);
dm_io_client_destroy(c->dm_io);
kfree(c);
}
EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
static unsigned get_max_age_hz(void)
{
unsigned max_age = ACCESS_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 (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 retain_target = get_retain_buffers(c);
unsigned count;
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--;
dm_bufio_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);
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;
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(retain_bytes, dm_bufio_retain_bytes, uint, 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");