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/*
* 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/jiffies.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 inline_endio(struct bio *bio, int error)
{
bio_end_io_t *end_fn = bio->bi_private;
/*
* Reset the bio to free any attached resources
* (e.g. bio integrity profiles).
*/
bio_reset(bio);
end_fn(bio, error);
}
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 = inline_endio;
/*
* Use of .bi_private isn't a problem here because
* the dm_buffer's inline bio is local to bufio.
*/
b->bio.bi_private = 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();
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 time_after_eq(jiffies, b->last_accessed + age_hz);
}
static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
{
struct dm_buffer *b, *tmp;
unsigned 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");
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