// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2009-2011 Red Hat, Inc.
*
* Author: Mikulas Patocka <[email protected]>
*
* This file is released under the GPL.
*/
#include <linux/dm-bufio.h>
#include <linux/device-mapper.h>
#include <linux/dm-io.h>
#include <linux/slab.h>
#include <linux/sched/mm.h>
#include <linux/jiffies.h>
#include <linux/vmalloc.h>
#include <linux/shrinker.h>
#include <linux/module.h>
#include <linux/rbtree.h>
#include <linux/stacktrace.h>
#include <linux/jump_label.h>
#include "dm.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_RATIO 3
#define DM_BUFIO_LOW_WATERMARK_RATIO 16
/*
* Check buffer ages in this interval (seconds)
*/
#define DM_BUFIO_WORK_TIMER_SECS 30
/*
* Free buffers when they are older than this (seconds)
*/
#define DM_BUFIO_DEFAULT_AGE_SECS 300
/*
* The nr of bytes of cached data to keep around.
*/
#define DM_BUFIO_DEFAULT_RETAIN_BYTES (256 * 1024)
/*
* Align buffer writes to this boundary.
* Tests show that SSDs have the highest IOPS when using 4k writes.
*/
#define DM_BUFIO_WRITE_ALIGN 4096
/*
* dm_buffer->list_mode
*/
#define LIST_CLEAN 0
#define LIST_DIRTY 1
#define LIST_SIZE 2
/*--------------------------------------------------------------*/
/*
* Rather than use an LRU list, we use a clock algorithm where entries
* are held in a circular list. When an entry is 'hit' a reference bit
* is set. The least recently used entry is approximated by running a
* cursor around the list selecting unreferenced entries. Referenced
* entries have their reference bit cleared as the cursor passes them.
*/
struct lru_entry {
struct list_head list;
atomic_t referenced;
};
struct lru_iter {
struct lru *lru;
struct list_head list;
struct lru_entry *stop;
struct lru_entry *e;
};
struct lru {
struct list_head *cursor;
unsigned long count;
struct list_head iterators;
};
/*--------------*/
static void lru_init(struct lru *lru)
{
lru->cursor = NULL;
lru->count = 0;
INIT_LIST_HEAD(&lru->iterators);
}
static void lru_destroy(struct lru *lru)
{
WARN_ON_ONCE(lru->cursor);
WARN_ON_ONCE(!list_empty(&lru->iterators));
}
/*
* Insert a new entry into the lru.
*/
static void lru_insert(struct lru *lru, struct lru_entry *le)
{
/*
* Don't be tempted to set to 1, makes the lru aspect
* perform poorly.
*/
atomic_set(&le->referenced, 0);
if (lru->cursor) {
list_add_tail(&le->list, lru->cursor);
} else {
INIT_LIST_HEAD(&le->list);
lru->cursor = &le->list;
}
lru->count++;
}
/*--------------*/
/*
* Convert a list_head pointer to an lru_entry pointer.
*/
static inline struct lru_entry *to_le(struct list_head *l)
{
return container_of(l, struct lru_entry, list);
}
/*
* Initialize an lru_iter and add it to the list of cursors in the lru.
*/
static void lru_iter_begin(struct lru *lru, struct lru_iter *it)
{
it->lru = lru;
it->stop = lru->cursor ? to_le(lru->cursor->prev) : NULL;
it->e = lru->cursor ? to_le(lru->cursor) : NULL;
list_add(&it->list, &lru->iterators);
}
/*
* Remove an lru_iter from the list of cursors in the lru.
*/
static inline void lru_iter_end(struct lru_iter *it)
{
list_del(&it->list);
}
/* Predicate function type to be used with lru_iter_next */
typedef bool (*iter_predicate)(struct lru_entry *le, void *context);
/*
* Advance the cursor to the next entry that passes the
* predicate, and return that entry. Returns NULL if the
* iteration is complete.
*/
static struct lru_entry *lru_iter_next(struct lru_iter *it,
iter_predicate pred, void *context)
{
struct lru_entry *e;
while (it->e) {
e = it->e;
/* advance the cursor */
if (it->e == it->stop)
it->e = NULL;
else
it->e = to_le(it->e->list.next);
if (pred(e, context))
return e;
}
return NULL;
}
/*
* Invalidate a specific lru_entry and update all cursors in
* the lru accordingly.
*/
static void lru_iter_invalidate(struct lru *lru, struct lru_entry *e)
{
struct lru_iter *it;
list_for_each_entry(it, &lru->iterators, list) {
/* Move c->e forwards if necc. */
if (it->e == e) {
it->e = to_le(it->e->list.next);
if (it->e == e)
it->e = NULL;
}
/* Move it->stop backwards if necc. */
if (it->stop == e) {
it->stop = to_le(it->stop->list.prev);
if (it->stop == e)
it->stop = NULL;
}
}
}
/*--------------*/
/*
* Remove a specific entry from the lru.
*/
static void lru_remove(struct lru *lru, struct lru_entry *le)
{
lru_iter_invalidate(lru, le);
if (lru->count == 1) {
lru->cursor = NULL;
} else {
if (lru->cursor == &le->list)
lru->cursor = lru->cursor->next;
list_del(&le->list);
}
lru->count--;
}
/*
* Mark as referenced.
*/
static inline void lru_reference(struct lru_entry *le)
{
atomic_set(&le->referenced, 1);
}
/*--------------*/
/*
* Remove the least recently used entry (approx), that passes the predicate.
* Returns NULL on failure.
*/
enum evict_result {
ER_EVICT,
ER_DONT_EVICT,
ER_STOP, /* stop looking for something to evict */
};
typedef enum evict_result (*le_predicate)(struct lru_entry *le, void *context);
static struct lru_entry *lru_evict(struct lru *lru, le_predicate pred, void *context, bool no_sleep)
{
unsigned long tested = 0;
struct list_head *h = lru->cursor;
struct lru_entry *le;
if (!h)
return NULL;
/*
* In the worst case we have to loop around twice. Once to clear
* the reference flags, and then again to discover the predicate
* fails for all entries.
*/
while (tested < lru->count) {
le = container_of(h, struct lru_entry, list);
if (atomic_read(&le->referenced)) {
atomic_set(&le->referenced, 0);
} else {
tested++;
switch (pred(le, context)) {
case ER_EVICT:
/*
* Adjust the cursor, so we start the next
* search from here.
*/
lru->cursor = le->list.next;
lru_remove(lru, le);
return le;
case ER_DONT_EVICT:
break;
case ER_STOP:
lru->cursor = le->list.next;
return NULL;
}
}
h = h->next;
if (!no_sleep)
cond_resched();
}
return NULL;
}
/*--------------------------------------------------------------*/
/*
* 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 {
/* protected by the locks in dm_buffer_cache */
struct rb_node node;
/* immutable, so don't need protecting */
sector_t block;
void *data;
unsigned char data_mode; /* DATA_MODE_* */
/*
* These two fields are used in isolation, so do not need
* a surrounding lock.
*/
atomic_t hold_count;
unsigned long last_accessed;
/*
* Everything else is protected by the mutex in
* dm_bufio_client
*/
unsigned long state;
struct lru_entry lru;
unsigned char list_mode; /* LIST_* */
blk_status_t read_error;
blk_status_t write_error;
unsigned int dirty_start;
unsigned int dirty_end;
unsigned int write_start;
unsigned int write_end;
struct list_head write_list;
struct dm_bufio_client *c;
void (*end_io)(struct dm_buffer *b, blk_status_t bs);
#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
#define MAX_STACK 10
unsigned int stack_len;
unsigned long stack_entries[MAX_STACK];
#endif
};
/*--------------------------------------------------------------*/
/*
* The buffer cache manages buffers, particularly:
* - inc/dec of holder count
* - setting the last_accessed field
* - maintains clean/dirty state along with lru
* - selecting buffers that match predicates
*
* It does *not* handle:
* - allocation/freeing of buffers.
* - IO
* - Eviction or cache sizing.
*
* cache_get() and cache_put() are threadsafe, you do not need to
* protect these calls with a surrounding mutex. All the other
* methods are not threadsafe; they do use locking primitives, but
* only enough to ensure get/put are threadsafe.
*/
struct buffer_tree {
union {
struct rw_semaphore lock;
rwlock_t spinlock;
} u;
struct rb_root root;
} ____cacheline_aligned_in_smp;
struct dm_buffer_cache {
struct lru lru[LIST_SIZE];
/*
* We spread entries across multiple trees to reduce contention
* on the locks.
*/
unsigned int num_locks;
bool no_sleep;
struct buffer_tree trees[];
};
static DEFINE_STATIC_KEY_FALSE(no_sleep_enabled);
static inline unsigned int cache_index(sector_t block, unsigned int num_locks)
{
return dm_hash_locks_index(block, num_locks);
}
static inline void cache_read_lock(struct dm_buffer_cache *bc, sector_t block)
{
if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
read_lock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
else
down_read(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
}
static inline void cache_read_unlock(struct dm_buffer_cache *bc, sector_t block)
{
if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
read_unlock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
else
up_read(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
}
static inline void cache_write_lock(struct dm_buffer_cache *bc, sector_t block)
{
if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
write_lock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
else
down_write(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
}
static inline void cache_write_unlock(struct dm_buffer_cache *bc, sector_t block)
{
if (static_branch_unlikely(&no_sleep_enabled) && bc->no_sleep)
write_unlock_bh(&bc->trees[cache_index(block, bc->num_locks)].u.spinlock);
else
up_write(&bc->trees[cache_index(block, bc->num_locks)].u.lock);
}
/*
* Sometimes we want to repeatedly get and drop locks as part of an iteration.
* This struct helps avoid redundant drop and gets of the same lock.
*/
struct lock_history {
struct dm_buffer_cache *cache;
bool write;
unsigned int previous;
unsigned int no_previous;
};
static void lh_init(struct lock_history *lh, struct dm_buffer_cache *cache, bool write)
{
lh->cache = cache;
lh->write = write;
lh->no_previous = cache->num_locks;
lh->previous = lh->no_previous;
}
static void __lh_lock(struct lock_history *lh, unsigned int index)
{
if (lh->write) {
if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
write_lock_bh(&lh->cache->trees[index].u.spinlock);
else
down_write(&lh->cache->trees[index].u.lock);
} else {
if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
read_lock_bh(&lh->cache->trees[index].u.spinlock);
else
down_read(&lh->cache->trees[index].u.lock);
}
}
static void __lh_unlock(struct lock_history *lh, unsigned int index)
{
if (lh->write) {
if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
write_unlock_bh(&lh->cache->trees[index].u.spinlock);
else
up_write(&lh->cache->trees[index].u.lock);
} else {
if (static_branch_unlikely(&no_sleep_enabled) && lh->cache->no_sleep)
read_unlock_bh(&lh->cache->trees[index].u.spinlock);
else
up_read(&lh->cache->trees[index].u.lock);
}
}
/*
* Make sure you call this since it will unlock the final lock.
*/
static void lh_exit(struct lock_history *lh)
{
if (lh->previous != lh->no_previous) {
__lh_unlock(lh, lh->previous);
lh->previous = lh->no_previous;
}
}
/*
* Named 'next' because there is no corresponding
* 'up/unlock' call since it's done automatically.
*/
static void lh_next(struct lock_history *lh, sector_t b)
{
unsigned int index = cache_index(b, lh->no_previous); /* no_previous is num_locks */
if (lh->previous != lh->no_previous) {
if (lh->previous != index) {
__lh_unlock(lh, lh->previous);
__lh_lock(lh, index);
lh->previous = index;
}
} else {
__lh_lock(lh, index);
lh->previous = index;
}
}
static inline struct dm_buffer *le_to_buffer(struct lru_entry *le)
{
return container_of(le, struct dm_buffer, lru);
}
static struct dm_buffer *list_to_buffer(struct list_head *l)
{
struct lru_entry *le = list_entry(l, struct lru_entry, list);
return le_to_buffer(le);
}
static void cache_init(struct dm_buffer_cache *bc, unsigned int num_locks, bool no_sleep)
{
unsigned int i;
bc->num_locks = num_locks;
bc->no_sleep = no_sleep;
for (i = 0; i < bc->num_locks; i++) {
if (no_sleep)
rwlock_init(&bc->trees[i].u.spinlock);
else
init_rwsem(&bc->trees[i].u.lock);
bc->trees[i].root = RB_ROOT;
}
lru_init(&bc->lru[LIST_CLEAN]);
lru_init(&bc->lru[LIST_DIRTY]);
}
static void cache_destroy(struct dm_buffer_cache *bc)
{
unsigned int i;
for (i = 0; i < bc->num_locks; i++)
WARN_ON_ONCE(!RB_EMPTY_ROOT(&bc->trees[i].root));
lru_destroy(&bc->lru[LIST_CLEAN]);
lru_destroy(&bc->lru[LIST_DIRTY]);
}
/*--------------*/
/*
* not threadsafe, or racey depending how you look at it
*/
static inline unsigned long cache_count(struct dm_buffer_cache *bc, int list_mode)
{
return bc->lru[list_mode].count;
}
static inline unsigned long cache_total(struct dm_buffer_cache *bc)
{
return cache_count(bc, LIST_CLEAN) + cache_count(bc, LIST_DIRTY);
}
/*--------------*/
/*
* Gets a specific buffer, indexed by block.
* If the buffer is found then its holder count will be incremented and
* lru_reference will be called.
*
* threadsafe
*/
static struct dm_buffer *__cache_get(const struct rb_root *root, sector_t block)
{
struct rb_node *n = root->rb_node;
struct dm_buffer *b;
while (n) {
b = container_of(n, struct dm_buffer, node);
if (b->block == block)
return b;
n = block < b->block ? n->rb_left : n->rb_right;
}
return NULL;
}
static void __cache_inc_buffer(struct dm_buffer *b)
{
atomic_inc(&b->hold_count);
WRITE_ONCE(b->last_accessed, jiffies);
}
static struct dm_buffer *cache_get(struct dm_buffer_cache *bc, sector_t block)
{
struct dm_buffer *b;
cache_read_lock(bc, block);
b = __cache_get(&bc->trees[cache_index(block, bc->num_locks)].root, block);
if (b) {
lru_reference(&b->lru);
__cache_inc_buffer(b);
}
cache_read_unlock(bc, block);
return b;
}
/*--------------*/
/*
* Returns true if the hold count hits zero.
* threadsafe
*/
static bool cache_put(struct dm_buffer_cache *bc, struct dm_buffer *b)
{
bool r;
cache_read_lock(bc, b->block);
BUG_ON(!atomic_read(&b->hold_count));
r = atomic_dec_and_test(&b->hold_count);
cache_read_unlock(bc, b->block);
return r;
}
/*--------------*/
typedef enum evict_result (*b_predicate)(struct dm_buffer *, void *);
/*
* Evicts a buffer based on a predicate. The oldest buffer that
* matches the predicate will be selected. In addition to the
* predicate the hold_count of the selected buffer will be zero.
*/
struct evict_wrapper {
struct lock_history *lh;
b_predicate pred;
void *context;
};
/*
* Wraps the buffer predicate turning it into an lru predicate. Adds
* extra test for hold_count.
*/
static enum evict_result __evict_pred(struct lru_entry *le, void *context)
{
struct evict_wrapper *w = context;
struct dm_buffer *b = le_to_buffer(le);
lh_next(w->lh, b->block);
if (atomic_read(&b->hold_count))
return ER_DONT_EVICT;
return w->pred(b, w->context);
}
static struct dm_buffer *__cache_evict(struct dm_buffer_cache *bc, int list_mode,
b_predicate pred, void *context,
struct lock_history *lh)
{
struct evict_wrapper w = {.lh = lh, .pred = pred, .context = context};
struct lru_entry *le;
struct dm_buffer *b;
le = lru_evict(&bc->lru[list_mode], __evict_pred, &w, bc->no_sleep);
if (!le)
return NULL;
b = le_to_buffer(le);
/* __evict_pred will have locked the appropriate tree. */
rb_erase(&b->node, &bc->trees[cache_index(b->block, bc->num_locks)].root);
return b;
}
static struct dm_buffer *cache_evict(struct dm_buffer_cache *bc, int list_mode,
b_predicate pred, void *context)
{
struct dm_buffer *b;
struct lock_history lh;
lh_init(&lh, bc, true);
b = __cache_evict(bc, list_mode, pred, context, &lh);
lh_exit(&lh);
return b;
}
/*--------------*/
/*
* Mark a buffer as clean or dirty. Not threadsafe.
*/
static void cache_mark(struct dm_buffer_cache *bc, struct dm_buffer *b, int list_mode)
{
cache_write_lock(bc, b->block);
if (list_mode != b->list_mode) {
lru_remove(&bc->lru[b->list_mode], &b->lru);
b->list_mode = list_mode;
lru_insert(&bc->lru[b->list_mode], &b->lru);
}
cache_write_unlock(bc, b->block);
}
/*--------------*/
/*
* Runs through the lru associated with 'old_mode', if the predicate matches then
* it moves them to 'new_mode'. Not threadsafe.
*/
static void __cache_mark_many(struct dm_buffer_cache *bc, int old_mode, int new_mode,
b_predicate pred, void *context, struct lock_history *lh)
{
struct lru_entry *le;
struct dm_buffer *b;
struct evict_wrapper w = {.lh = lh, .pred = pred, .context = context};
while (true) {
le = lru_evict(&bc->lru[old_mode], __evict_pred, &w, bc->no_sleep);
if (!le)
break;
b = le_to_buffer(le);
b->list_mode = new_mode;
lru_insert(&bc->lru[b->list_mode], &b->lru);
}
}
static void cache_mark_many(struct dm_buffer_cache *bc, int old_mode, int new_mode,
b_predicate pred, void *context)
{
struct lock_history lh;
lh_init(&lh, bc, true);
__cache_mark_many(bc, old_mode, new_mode, pred, context, &lh);
lh_exit(&lh);
}
/*--------------*/
/*
* Iterates through all clean or dirty entries calling a function for each
* entry. The callback may terminate the iteration early. Not threadsafe.
*/
/*
* Iterator functions should return one of these actions to indicate
* how the iteration should proceed.
*/
enum it_action {
IT_NEXT,
IT_COMPLETE,
};
typedef enum it_action (*iter_fn)(struct dm_buffer *b, void *context);
static void __cache_iterate(struct dm_buffer_cache *bc, int list_mode,
iter_fn fn, void *context, struct lock_history *lh)
{
struct lru *lru = &bc->lru[list_mode];
struct lru_entry *le, *first;
if (!lru->cursor)
return;
first = le = to_le(lru->cursor);
do {
struct dm_buffer *b = le_to_buffer(le);
lh_next(lh, b->block);
switch (fn(b, context)) {
case IT_NEXT:
break;
case IT_COMPLETE:
return;
}
cond_resched();
le = to_le(le->list.next);
} while (le != first);
}
static void cache_iterate(struct dm_buffer_cache *bc, int list_mode,
iter_fn fn, void *context)
{
struct lock_history lh;
lh_init(&lh, bc, false);
__cache_iterate(bc, list_mode, fn, context, &lh);
lh_exit(&lh);
}
/*--------------*/
/*
* Passes ownership of the buffer to the cache. Returns false if the
* buffer was already present (in which case ownership does not pass).
* eg, a race with another thread.
*
* Holder count should be 1 on insertion.
*
* Not threadsafe.
*/
static bool __cache_insert(struct rb_root *root, struct dm_buffer *b)
{
struct rb_node **new = &root->rb_node, *parent = NULL;
struct dm_buffer *found;
while (*new) {
found = container_of(*new, struct dm_buffer, node);
if (found->block == b->block)
return false;
parent = *new;
new = b->block < found->block ?
&found->node.rb_left : &found->node.rb_right;
}
rb_link_node(&b->node, parent, new);
rb_insert_color(&b->node, root);
return true;
}
static bool cache_insert(struct dm_buffer_cache *bc, struct dm_buffer *b)
{
bool r;
if (WARN_ON_ONCE(b->list_mode >= LIST_SIZE))
return false;
cache_write_lock(bc, b->block);
BUG_ON(atomic_read(&b->hold_count) != 1);
r = __cache_insert(&bc->trees[cache_index(b->block, bc->num_locks)].root, b);
if (r)
lru_insert(&bc->lru[b->list_mode], &b->lru);
cache_write_unlock(bc, b->block);
return r;
}
/*--------------*/
/*
* Removes buffer from cache, ownership of the buffer passes back to the caller.
* Fails if the hold_count is not one (ie. the caller holds the only reference).
*
* Not threadsafe.
*/
static bool cache_remove(struct dm_buffer_cache *bc, struct dm_buffer *b)
{
bool r;
cache_write_lock(bc, b->block);
if (atomic_read(&b->hold_count) != 1) {
r = false;
} else {
r = true;
rb_erase(&b->node, &bc->trees[cache_index(b->block, bc->num_locks)].root);
lru_remove(&bc->lru[b->list_mode], &b->lru);
}
cache_write_unlock(bc, b->block);
return r;
}
/*--------------*/
typedef void (*b_release)(struct dm_buffer *);
static struct dm_buffer *__find_next(struct rb_root *root, sector_t block)
{
struct rb_node *n = root->rb_node;
struct dm_buffer *b;
struct dm_buffer *best = NULL;
while (n) {
b = container_of(n, struct dm_buffer, node);
if (b->block == block)
return b;
if (block <= b->block) {
n = n->rb_left;
best = b;
} else {
n = n->rb_right;
}
}
return best;
}
static void __remove_range(struct dm_buffer_cache *bc,
struct rb_root *root,
sector_t begin, sector_t end,
b_predicate pred, b_release release)
{
struct dm_buffer *b;
while (true) {
cond_resched();
b = __find_next(root, begin);
if (!b || (b->block >= end))
break;
begin = b->block + 1;
if (atomic_read(&b->hold_count))
continue;
if (pred(b, NULL) == ER_EVICT) {
rb_erase(&b->node, root);
lru_remove(&bc->lru[b->list_mode], &b->lru);
release(b);
}
}
}
static void cache_remove_range(struct dm_buffer_cache *bc,
sector_t begin, sector_t end,
b_predicate pred, b_release release)
{
unsigned int i;
BUG_ON(bc->no_sleep);
for (i = 0; i < bc->num_locks; i++) {
down_write(&bc->trees[i].u.lock);
__remove_range(bc, &bc->trees[i].root, begin, end, pred, release);
up_write(&bc->trees[i].u.lock);
}
}
/*----------------------------------------------------------------*/
/*
* Linking of buffers:
* All buffers are linked to buffer_cache with their node 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 block_device *bdev;
unsigned int block_size;
s8 sectors_per_block_bits;
bool no_sleep;
struct mutex lock;
spinlock_t spinlock;
int async_write_error;
void (*alloc_callback)(struct dm_buffer *buf);
void (*write_callback)(struct dm_buffer *buf);
struct kmem_cache *slab_buffer;
struct kmem_cache *slab_cache;
struct dm_io_client *dm_io;
struct list_head reserved_buffers;
unsigned int need_reserved_buffers;
unsigned int minimum_buffers;
sector_t start;
struct shrinker *shrinker;
struct work_struct shrink_work;
atomic_long_t need_shrink;
wait_queue_head_t free_buffer_wait;
struct list_head client_list;
/*
* Used by global_cleanup to sort the clients list.
*/
unsigned long oldest_buffer;
struct dm_buffer_cache cache; /* must be last member */
};
/*----------------------------------------------------------------*/
#define dm_bufio_in_request() (!!current->bio_list)
static void dm_bufio_lock(struct dm_bufio_client *c)
{
if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
spin_lock_bh(&c->spinlock);
else
mutex_lock_nested(&c->lock, dm_bufio_in_request());
}
static void dm_bufio_unlock(struct dm_bufio_client *c)
{
if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
spin_unlock_bh(&c->spinlock);
else
mutex_unlock(&c->lock);
}
/*----------------------------------------------------------------*/
/*
* Default cache size: available memory divided by the ratio.
*/
static unsigned long dm_bufio_default_cache_size;
/*
* Total cache size set by the user.
*/
static unsigned long dm_bufio_cache_size;
/*
* A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
* at any time. If it disagrees, the user has changed cache size.
*/
static unsigned long dm_bufio_cache_size_latch;
static DEFINE_SPINLOCK(global_spinlock);
/*
* Buffers are freed after this timeout
*/
static unsigned int dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
static unsigned long dm_bufio_peak_allocated;
static unsigned long dm_bufio_allocated_kmem_cache;
static unsigned long dm_bufio_allocated_get_free_pages;
static unsigned long dm_bufio_allocated_vmalloc;
static unsigned long dm_bufio_current_allocated;
/*----------------------------------------------------------------*/
/*
* 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 and dm_bufio_client_count
*/
static DEFINE_MUTEX(dm_bufio_clients_lock);
static struct workqueue_struct *dm_bufio_wq;
static struct delayed_work dm_bufio_cleanup_old_work;
static struct work_struct dm_bufio_replacement_work;
#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
static void buffer_record_stack(struct dm_buffer *b)
{
b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);
}
#endif
/*----------------------------------------------------------------*/
static void adjust_total_allocated(struct dm_buffer *b, bool unlink)
{
unsigned char data_mode;
long diff;
static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
&dm_bufio_allocated_kmem_cache,
&dm_bufio_allocated_get_free_pages,
&dm_bufio_allocated_vmalloc,
};
data_mode = b->data_mode;
diff = (long)b->c->block_size;
if (unlink)
diff = -diff;
spin_lock(&global_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;
if (!unlink) {
if (dm_bufio_current_allocated > dm_bufio_cache_size)
queue_work(dm_bufio_wq, &dm_bufio_replacement_work);
}
spin_unlock(&global_spinlock);
}
/*
* Change the number of clients and recalculate per-client limit.
*/
static void __cache_size_refresh(void)
{
if (WARN_ON(!mutex_is_locked(&dm_bufio_clients_lock)))
return;
if (WARN_ON(dm_bufio_client_count < 0))
return;
dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size);
/*
* Use default if set to 0 and report the actual cache size used.
*/
if (!dm_bufio_cache_size_latch) {
(void)cmpxchg(&dm_bufio_cache_size, 0,
dm_bufio_default_cache_size);
dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
}
}
/*
* 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_PAGE_ORDER).
*
* If the allocation shouldn't fail we use __vmalloc. This is only for the
* initial reserve allocation, so there's no risk of wasting all vmalloc
* space.
*/
static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
unsigned char *data_mode)
{
if (unlikely(c->slab_cache != NULL)) {
*data_mode = DATA_MODE_SLAB;
return kmem_cache_alloc(c->slab_cache, gfp_mask);
}
if (c->block_size <= KMALLOC_MAX_SIZE &&
gfp_mask & __GFP_NORETRY) {
*data_mode = DATA_MODE_GET_FREE_PAGES;
return (void *)__get_free_pages(gfp_mask,
c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
}
*data_mode = DATA_MODE_VMALLOC;
return __vmalloc(c->block_size, gfp_mask);
}
/*
* Free buffer's data.
*/
static void free_buffer_data(struct dm_bufio_client *c,
void *data, unsigned char data_mode)
{
switch (data_mode) {
case DATA_MODE_SLAB:
kmem_cache_free(c->slab_cache, data);
break;
case DATA_MODE_GET_FREE_PAGES:
free_pages((unsigned long)data,
c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
break;
case DATA_MODE_VMALLOC:
vfree(data);
break;
default:
DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
data_mode);
BUG();
}
}
/*
* Allocate buffer and its data.
*/
static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
{
struct dm_buffer *b = kmem_cache_alloc(c->slab_buffer, gfp_mask);
if (!b)
return NULL;
b->c = c;
b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
if (!b->data) {
kmem_cache_free(c->slab_buffer, b);
return NULL;
}
adjust_total_allocated(b, false);
#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
b->stack_len = 0;
#endif
return b;
}
/*
* Free buffer and its data.
*/
static void free_buffer(struct dm_buffer *b)
{
struct dm_bufio_client *c = b->c;
adjust_total_allocated(b, true);
free_buffer_data(c, b->data, b->data_mode);
kmem_cache_free(c->slab_buffer, b);
}
/*
*--------------------------------------------------------------------------
* Submit I/O on the buffer.
*
* Bio interface is faster but it has some problems:
* the vector list is limited (increasing this limit increases
* memory-consumption per buffer, so it is not viable);
*
* the memory must be direct-mapped, not vmalloced;
*
* If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
* it is not vmalloced, try using the bio interface.
*
* If the buffer is big, if it is vmalloced or if the underlying device
* rejects the bio because it is too large, use dm-io layer to do the I/O.
* The dm-io layer splits the I/O into multiple requests, avoiding the above
* shortcomings.
*--------------------------------------------------------------------------
*/
/*
* dm-io completion routine. It just calls b->bio.bi_end_io, pretending
* that the request was handled directly with bio interface.
*/
static void dmio_complete(unsigned long error, void *context)
{
struct dm_buffer *b = context;
b->end_io(b, unlikely(error != 0) ? BLK_STS_IOERR : 0);
}
static void use_dmio(struct dm_buffer *b, enum req_op op, sector_t sector,
unsigned int n_sectors, unsigned int offset,
unsigned short ioprio)
{
int r;
struct dm_io_request io_req = {
.bi_opf = op,
.notify.fn = dmio_complete,
.notify.context = b,
.client = b->c->dm_io,
};
struct dm_io_region region = {
.bdev = b->c->bdev,
.sector = sector,
.count = n_sectors,
};
if (b->data_mode != DATA_MODE_VMALLOC) {
io_req.mem.type = DM_IO_KMEM;
io_req.mem.ptr.addr = (char *)b->data + offset;
} else {
io_req.mem.type = DM_IO_VMA;
io_req.mem.ptr.vma = (char *)b->data + offset;
}
r = dm_io(&io_req, 1, ®ion, NULL, ioprio);
if (unlikely(r))
b->end_io(b, errno_to_blk_status(r));
}
static void bio_complete(struct bio *bio)
{
struct dm_buffer *b = bio->bi_private;
blk_status_t status = bio->bi_status;
bio_uninit(bio);
kfree(bio);
b->end_io(b, status);
}
static void use_bio(struct dm_buffer *b, enum req_op op, sector_t sector,
unsigned int n_sectors, unsigned int offset,
unsigned short ioprio)
{
struct bio *bio;
char *ptr;
unsigned int len;
bio = bio_kmalloc(1, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOWARN);
if (!bio) {
use_dmio(b, op, sector, n_sectors, offset, ioprio);
return;
}
bio_init(bio, b->c->bdev, bio->bi_inline_vecs, 1, op);
bio->bi_iter.bi_sector = sector;
bio->bi_end_io = bio_complete;
bio->bi_private = b;
bio->bi_ioprio = ioprio;
ptr = (char *)b->data + offset;
len = n_sectors << SECTOR_SHIFT;
__bio_add_page(bio, virt_to_page(ptr), len, offset_in_page(ptr));
submit_bio(bio);
}
static inline sector_t block_to_sector(struct dm_bufio_client *c, sector_t block)
{
sector_t sector;
if (likely(c->sectors_per_block_bits >= 0))
sector = block << c->sectors_per_block_bits;
else
sector = block * (c->block_size >> SECTOR_SHIFT);
sector += c->start;
return sector;
}
static void submit_io(struct dm_buffer *b, enum req_op op, unsigned short ioprio,
void (*end_io)(struct dm_buffer *, blk_status_t))
{
unsigned int n_sectors;
sector_t sector;
unsigned int offset, end;
b->end_io = end_io;
sector = block_to_sector(b->c, b->block);
if (op != REQ_OP_WRITE) {
n_sectors = b->c->block_size >> SECTOR_SHIFT;
offset = 0;
} else {
if (b->c->write_callback)
b->c->write_callback(b);
offset = b->write_start;
end = b->write_end;
offset &= -DM_BUFIO_WRITE_ALIGN;
end += DM_BUFIO_WRITE_ALIGN - 1;
end &= -DM_BUFIO_WRITE_ALIGN;
if (unlikely(end > b->c->block_size))
end = b->c->block_size;
sector += offset >> SECTOR_SHIFT;
n_sectors = (end - offset) >> SECTOR_SHIFT;
}
if (b->data_mode != DATA_MODE_VMALLOC)
use_bio(b, op, sector, n_sectors, offset, ioprio);
else
use_dmio(b, op, sector, n_sectors, offset, ioprio);
}
/*
*--------------------------------------------------------------
* Writing dirty buffers
*--------------------------------------------------------------
*/
/*
* The endio routine for write.
*
* Set the error, clear B_WRITING bit and wake anyone who was waiting on
* it.
*/
static void write_endio(struct dm_buffer *b, blk_status_t status)
{
b->write_error = status;
if (unlikely(status)) {
struct dm_bufio_client *c = b->c;
(void)cmpxchg(&c->async_write_error, 0,
blk_status_to_errno(status));
}
BUG_ON(!test_bit(B_WRITING, &b->state));
smp_mb__before_atomic();
clear_bit(B_WRITING, &b->state);
smp_mb__after_atomic();
wake_up_bit(&b->state, B_WRITING);
}
/*
* Initiate a write on a dirty buffer, but don't wait for it.
*
* - If the buffer is not dirty, exit.
* - If there some previous write going on, wait for it to finish (we can't
* have two writes on the same buffer simultaneously).
* - Submit our write and don't wait on it. We set B_WRITING indicating
* that there is a write in progress.
*/
static void __write_dirty_buffer(struct dm_buffer *b,
struct list_head *write_list)
{
if (!test_bit(B_DIRTY, &b->state))
return;
clear_bit(B_DIRTY, &b->state);
wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
b->write_start = b->dirty_start;
b->write_end = b->dirty_end;
if (!write_list)
submit_io(b, REQ_OP_WRITE, IOPRIO_DEFAULT, write_endio);
else
list_add_tail(&b->write_list, write_list);
}
static void __flush_write_list(struct list_head *write_list)
{
struct blk_plug plug;
blk_start_plug(&plug);
while (!list_empty(write_list)) {
struct dm_buffer *b =
list_entry(write_list->next, struct dm_buffer, write_list);
list_del(&b->write_list);
submit_io(b, REQ_OP_WRITE, IOPRIO_DEFAULT, write_endio);
cond_resched();
}
blk_finish_plug(&plug);
}
/*
* Wait until any activity on the buffer finishes. Possibly write the
* buffer if it is dirty. When this function finishes, there is no I/O
* running on the buffer and the buffer is not dirty.
*/
static void __make_buffer_clean(struct dm_buffer *b)
{
BUG_ON(atomic_read(&b->hold_count));
/* smp_load_acquire() pairs with read_endio()'s smp_mb__before_atomic() */
if (!smp_load_acquire(&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);
}
static enum evict_result is_clean(struct dm_buffer *b, void *context)
{
struct dm_bufio_client *c = context;
/* These should never happen */
if (WARN_ON_ONCE(test_bit(B_WRITING, &b->state)))
return ER_DONT_EVICT;
if (WARN_ON_ONCE(test_bit(B_DIRTY, &b->state)))
return ER_DONT_EVICT;
if (WARN_ON_ONCE(b->list_mode != LIST_CLEAN))
return ER_DONT_EVICT;
if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep &&
unlikely(test_bit(B_READING, &b->state)))
return ER_DONT_EVICT;
return ER_EVICT;
}
static enum evict_result is_dirty(struct dm_buffer *b, void *context)
{
/* These should never happen */
if (WARN_ON_ONCE(test_bit(B_READING, &b->state)))
return ER_DONT_EVICT;
if (WARN_ON_ONCE(b->list_mode != LIST_DIRTY))
return ER_DONT_EVICT;
return ER_EVICT;
}
/*
* 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;
b = cache_evict(&c->cache, LIST_CLEAN, is_clean, c);
if (b) {
/* this also waits for pending reads */
__make_buffer_clean(b);
return b;
}
if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
return NULL;
b = cache_evict(&c->cache, LIST_DIRTY, is_dirty, NULL);
if (b) {
__make_buffer_clean(b);
return b;
}
return NULL;
}
/*
* Wait until some other threads free some buffer or release hold count on
* some buffer.
*
* This function is entered with c->lock held, drops it and regains it
* before exiting.
*/
static void __wait_for_free_buffer(struct dm_bufio_client *c)
{
DECLARE_WAITQUEUE(wait, current);
add_wait_queue(&c->free_buffer_wait, &wait);
set_current_state(TASK_UNINTERRUPTIBLE);
dm_bufio_unlock(c);
/*
* It's possible to miss a wake up event since we don't always
* hold c->lock when wake_up is called. So we have a timeout here,
* just in case.
*/
io_schedule_timeout(5 * HZ);
remove_wait_queue(&c->free_buffer_wait, &wait);
dm_bufio_lock(c);
}
enum new_flag {
NF_FRESH = 0,
NF_READ = 1,
NF_GET = 2,
NF_PREFETCH = 3
};
/*
* Allocate a new buffer. If the allocation is not possible, wait until
* some other thread frees a buffer.
*
* May drop the lock and regain it.
*/
static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
{
struct dm_buffer *b;
bool tried_noio_alloc = false;
/*
* dm-bufio is resistant to allocation failures (it just keeps
* one buffer reserved in cases all the allocations fail).
* So set flags to not try too hard:
* GFP_NOWAIT: don't wait; if we need to sleep we'll release our
* mutex and wait ourselves.
* __GFP_NORETRY: don't retry and rather return failure
* __GFP_NOMEMALLOC: don't use emergency reserves
* __GFP_NOWARN: don't print a warning in case of failure
*
* For debugging, if we set the cache size to 1, no new buffers will
* be allocated.
*/
while (1) {
if (dm_bufio_cache_size_latch != 1) {
b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
if (b)
return b;
}
if (nf == NF_PREFETCH)
return NULL;
if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
dm_bufio_unlock(c);
b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
dm_bufio_lock(c);
if (b)
return b;
tried_noio_alloc = true;
}
if (!list_empty(&c->reserved_buffers)) {
b = list_to_buffer(c->reserved_buffers.next);
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;
b->block = -1;
if (!c->need_reserved_buffers)
free_buffer(b);
else {
list_add(&b->lru.list, &c->reserved_buffers);
c->need_reserved_buffers--;
}
/*
* We hold the bufio lock here, so no one can add entries to the
* wait queue anyway.
*/
if (unlikely(waitqueue_active(&c->free_buffer_wait)))
wake_up(&c->free_buffer_wait);
}
static enum evict_result cleaned(struct dm_buffer *b, void *context)
{
if (WARN_ON_ONCE(test_bit(B_READING, &b->state)))
return ER_DONT_EVICT; /* should never happen */
if (test_bit(B_DIRTY, &b->state) || test_bit(B_WRITING, &b->state))
return ER_DONT_EVICT;
else
return ER_EVICT;
}
static void __move_clean_buffers(struct dm_bufio_client *c)
{
cache_mark_many(&c->cache, LIST_DIRTY, LIST_CLEAN, cleaned, NULL);
}
struct write_context {
int no_wait;
struct list_head *write_list;
};
static enum it_action write_one(struct dm_buffer *b, void *context)
{
struct write_context *wc = context;
if (wc->no_wait && test_bit(B_WRITING, &b->state))
return IT_COMPLETE;
__write_dirty_buffer(b, wc->write_list);
return IT_NEXT;
}
static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
struct list_head *write_list)
{
struct write_context wc = {.no_wait = no_wait, .write_list = write_list};
__move_clean_buffers(c);
cache_iterate(&c->cache, LIST_DIRTY, write_one, &wc);
}
/*
* 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)
{
if (cache_count(&c->cache, LIST_DIRTY) >
cache_count(&c->cache, LIST_CLEAN) * DM_BUFIO_WRITEBACK_RATIO)
__write_dirty_buffers_async(c, 1, write_list);
}
/*
*--------------------------------------------------------------
* Getting a buffer
*--------------------------------------------------------------
*/
static void cache_put_and_wake(struct dm_bufio_client *c, struct dm_buffer *b)
{
/*
* Relying on waitqueue_active() is racey, but we sleep
* with schedule_timeout anyway.
*/
if (cache_put(&c->cache, b) &&
unlikely(waitqueue_active(&c->free_buffer_wait)))
wake_up(&c->free_buffer_wait);
}
/*
* This assumes you have already checked the cache to see if the buffer
* is already present (it will recheck after dropping the lock for allocation).
*/
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;
/* This can't be called with NF_GET */
if (WARN_ON_ONCE(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 buffer tree.
*/
b = cache_get(&c->cache, block);
if (b) {
__free_buffer_wake(new_b);
goto found_buffer;
}
__check_watermark(c, write_list);
b = new_b;
atomic_set(&b->hold_count, 1);
WRITE_ONCE(b->last_accessed, jiffies);
b->block = block;
b->read_error = 0;
b->write_error = 0;
b->list_mode = LIST_CLEAN;
if (nf == NF_FRESH)
b->state = 0;
else {
b->state = 1 << B_READING;
*need_submit = 1;
}
/*
* We mustn't insert into the cache until the B_READING state
* is set. Otherwise another thread could get it and use
* it before it had been read.
*/
cache_insert(&c->cache, b);
return b;
found_buffer:
if (nf == NF_PREFETCH) {
cache_put_and_wake(c, b);
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_acquire(B_READING, &b->state))) {
cache_put_and_wake(c, b);
return NULL;
}
return b;
}
/*
* The endio routine for reading: set the error, clear the bit and wake up
* anyone waiting on the buffer.
*/
static void read_endio(struct dm_buffer *b, blk_status_t status)
{
b->read_error = status;
BUG_ON(!test_bit(B_READING, &b->state));
smp_mb__before_atomic();
clear_bit(B_READING, &b->state);
smp_mb__after_atomic();
wake_up_bit(&b->state, B_READING);
}
/*
* A common routine for dm_bufio_new and dm_bufio_read. Operation of these
* functions is similar except that dm_bufio_new doesn't read the
* buffer from the disk (assuming that the caller overwrites all the data
* and uses dm_bufio_mark_buffer_dirty to write new data back).
*/
static void *new_read(struct dm_bufio_client *c, sector_t block,
enum new_flag nf, struct dm_buffer **bp,
unsigned short ioprio)
{
int need_submit = 0;
struct dm_buffer *b;
LIST_HEAD(write_list);
*bp = NULL;
/*
* Fast path, hopefully the block is already in the cache. No need
* to get the client lock for this.
*/
b = cache_get(&c->cache, block);
if (b) {
if (nf == NF_PREFETCH) {
cache_put_and_wake(c, b);
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_acquire(B_READING, &b->state))) {
cache_put_and_wake(c, b);
return NULL;
}
}
if (!b) {
if (nf == NF_GET)
return NULL;
dm_bufio_lock(c);
b = __bufio_new(c, block, nf, &need_submit, &write_list);
dm_bufio_unlock(c);
}
#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
if (b && (atomic_read(&b->hold_count) == 1))
buffer_record_stack(b);
#endif
__flush_write_list(&write_list);
if (!b)
return NULL;
if (need_submit)
submit_io(b, REQ_OP_READ, ioprio, read_endio);
if (nf != NF_GET) /* we already tested this condition above */
wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
if (b->read_error) {
int error = blk_status_to_errno(b->read_error);
dm_bufio_release(b);
return ERR_PTR(error);
}
*bp = b;
return b->data;
}
void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
struct dm_buffer **bp)
{
return new_read(c, block, NF_GET, bp, IOPRIO_DEFAULT);
}
EXPORT_SYMBOL_GPL(dm_bufio_get);
static void *__dm_bufio_read(struct dm_bufio_client *c, sector_t block,
struct dm_buffer **bp, unsigned short ioprio)
{
if (WARN_ON_ONCE(dm_bufio_in_request()))
return ERR_PTR(-EINVAL);
return new_read(c, block, NF_READ, bp, ioprio);
}
void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
struct dm_buffer **bp)
{
return __dm_bufio_read(c, block, bp, IOPRIO_DEFAULT);
}
EXPORT_SYMBOL_GPL(dm_bufio_read);
void *dm_bufio_read_with_ioprio(struct dm_bufio_client *c, sector_t block,
struct dm_buffer **bp, unsigned short ioprio)
{
return __dm_bufio_read(c, block, bp, ioprio);
}
EXPORT_SYMBOL_GPL(dm_bufio_read_with_ioprio);
void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
struct dm_buffer **bp)
{
if (WARN_ON_ONCE(dm_bufio_in_request()))
return ERR_PTR(-EINVAL);
return new_read(c, block, NF_FRESH, bp, IOPRIO_DEFAULT);
}
EXPORT_SYMBOL_GPL(dm_bufio_new);
static void __dm_bufio_prefetch(struct dm_bufio_client *c,
sector_t block, unsigned int n_blocks,
unsigned short ioprio)
{
struct blk_plug plug;
LIST_HEAD(write_list);
if (WARN_ON_ONCE(dm_bufio_in_request()))
return; /* should never happen */
blk_start_plug(&plug);
for (; n_blocks--; block++) {
int need_submit;
struct dm_buffer *b;
b = cache_get(&c->cache, block);
if (b) {
/* already in cache */
cache_put_and_wake(c, b);
continue;
}
dm_bufio_lock(c);
b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
&write_list);
if (unlikely(!list_empty(&write_list))) {
dm_bufio_unlock(c);
blk_finish_plug(&plug);
__flush_write_list(&write_list);
blk_start_plug(&plug);
dm_bufio_lock(c);
}
if (unlikely(b != NULL)) {
dm_bufio_unlock(c);
if (need_submit)
submit_io(b, REQ_OP_READ, ioprio, read_endio);
dm_bufio_release(b);
cond_resched();
if (!n_blocks)
goto flush_plug;
dm_bufio_lock(c);
}
dm_bufio_unlock(c);
}
flush_plug:
blk_finish_plug(&plug);
}
void dm_bufio_prefetch(struct dm_bufio_client *c, sector_t block, unsigned int n_blocks)
{
return __dm_bufio_prefetch(c, block, n_blocks, IOPRIO_DEFAULT);
}
EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
void dm_bufio_prefetch_with_ioprio(struct dm_bufio_client *c, sector_t block,
unsigned int n_blocks, unsigned short ioprio)
{
return __dm_bufio_prefetch(c, block, n_blocks, ioprio);
}
EXPORT_SYMBOL_GPL(dm_bufio_prefetch_with_ioprio);
void dm_bufio_release(struct dm_buffer *b)
{
struct dm_bufio_client *c = b->c;
/*
* 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_acquire(B_READING, &b->state) &&
!test_bit(B_WRITING, &b->state) &&
!test_bit(B_DIRTY, &b->state)) {
dm_bufio_lock(c);
/* cache remove can fail if there are other holders */
if (cache_remove(&c->cache, b)) {
__free_buffer_wake(b);
dm_bufio_unlock(c);
return;
}
dm_bufio_unlock(c);
}
cache_put_and_wake(c, b);
}
EXPORT_SYMBOL_GPL(dm_bufio_release);
void dm_bufio_mark_partial_buffer_dirty(struct dm_buffer *b,
unsigned int start, unsigned int end)
{
struct dm_bufio_client *c = b->c;
BUG_ON(start >= end);
BUG_ON(end > b->c->block_size);
dm_bufio_lock(c);
BUG_ON(test_bit(B_READING, &b->state));
if (!test_and_set_bit(B_DIRTY, &b->state)) {
b->dirty_start = start;
b->dirty_end = end;
cache_mark(&c->cache, b, LIST_DIRTY);
} else {
if (start < b->dirty_start)
b->dirty_start = start;
if (end > b->dirty_end)
b->dirty_end = end;
}
dm_bufio_unlock(c);
}
EXPORT_SYMBOL_GPL(dm_bufio_mark_partial_buffer_dirty);
void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
{
dm_bufio_mark_partial_buffer_dirty(b, 0, b->c->block_size);
}
EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
{
LIST_HEAD(write_list);
if (WARN_ON_ONCE(dm_bufio_in_request()))
return; /* should never happen */
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.
*/
static bool is_writing(struct lru_entry *e, void *context)
{
struct dm_buffer *b = le_to_buffer(e);
return test_bit(B_WRITING, &b->state);
}
int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
{
int a, f;
unsigned long nr_buffers;
struct lru_entry *e;
struct lru_iter it;
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);
nr_buffers = cache_count(&c->cache, LIST_DIRTY);
lru_iter_begin(&c->cache.lru[LIST_DIRTY], &it);
while ((e = lru_iter_next(&it, is_writing, c))) {
struct dm_buffer *b = le_to_buffer(e);
__cache_inc_buffer(b);
BUG_ON(test_bit(B_READING, &b->state));
if (nr_buffers) {
nr_buffers--;
dm_bufio_unlock(c);
wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
dm_bufio_lock(c);
} else {
wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
}
if (!test_bit(B_DIRTY, &b->state) && !test_bit(B_WRITING, &b->state))
cache_mark(&c->cache, b, LIST_CLEAN);
cache_put_and_wake(c, b);
cond_resched();
}
lru_iter_end(&it);
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 an empty barrier to flush the device.
*/
int dm_bufio_issue_flush(struct dm_bufio_client *c)
{
struct dm_io_request io_req = {
.bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC,
.mem.type = DM_IO_KMEM,
.mem.ptr.addr = NULL,
.client = c->dm_io,
};
struct dm_io_region io_reg = {
.bdev = c->bdev,
.sector = 0,
.count = 0,
};
if (WARN_ON_ONCE(dm_bufio_in_request()))
return -EINVAL;
return dm_io(&io_req, 1, &io_reg, NULL, IOPRIO_DEFAULT);
}
EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
/*
* Use dm-io to send a discard request to flush the device.
*/
int dm_bufio_issue_discard(struct dm_bufio_client *c, sector_t block, sector_t count)
{
struct dm_io_request io_req = {
.bi_opf = REQ_OP_DISCARD | REQ_SYNC,
.mem.type = DM_IO_KMEM,
.mem.ptr.addr = NULL,
.client = c->dm_io,
};
struct dm_io_region io_reg = {
.bdev = c->bdev,
.sector = block_to_sector(c, block),
.count = block_to_sector(c, count),
};
if (WARN_ON_ONCE(dm_bufio_in_request()))
return -EINVAL; /* discards are optional */
return dm_io(&io_req, 1, &io_reg, NULL, IOPRIO_DEFAULT);
}
EXPORT_SYMBOL_GPL(dm_bufio_issue_discard);
static bool forget_buffer(struct dm_bufio_client *c, sector_t block)
{
struct dm_buffer *b;
b = cache_get(&c->cache, block);
if (b) {
if (likely(!smp_load_acquire(&b->state))) {
if (cache_remove(&c->cache, b))
__free_buffer_wake(b);
else
cache_put_and_wake(c, b);
} else {
cache_put_and_wake(c, b);
}
}
return b ? true : false;
}
/*
* 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)
{
dm_bufio_lock(c);
forget_buffer(c, block);
dm_bufio_unlock(c);
}
EXPORT_SYMBOL_GPL(dm_bufio_forget);
static enum evict_result idle(struct dm_buffer *b, void *context)
{
return b->state ? ER_DONT_EVICT : ER_EVICT;
}
void dm_bufio_forget_buffers(struct dm_bufio_client *c, sector_t block, sector_t n_blocks)
{
dm_bufio_lock(c);
cache_remove_range(&c->cache, block, block + n_blocks, idle, __free_buffer_wake);
dm_bufio_unlock(c);
}
EXPORT_SYMBOL_GPL(dm_bufio_forget_buffers);
void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned int n)
{
c->minimum_buffers = n;
}
EXPORT_SYMBOL_GPL(dm_bufio_set_minimum_buffers);
unsigned int dm_bufio_get_block_size(struct dm_bufio_client *c)
{
return c->block_size;
}
EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
{
sector_t s = bdev_nr_sectors(c->bdev);
if (s >= c->start)
s -= c->start;
else
s = 0;
if (likely(c->sectors_per_block_bits >= 0))
s >>= c->sectors_per_block_bits;
else
sector_div(s, c->block_size >> SECTOR_SHIFT);
return s;
}
EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
struct dm_io_client *dm_bufio_get_dm_io_client(struct dm_bufio_client *c)
{
return c->dm_io;
}
EXPORT_SYMBOL_GPL(dm_bufio_get_dm_io_client);
sector_t dm_bufio_get_block_number(struct dm_buffer *b)
{
return b->block;
}
EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
void *dm_bufio_get_block_data(struct dm_buffer *b)
{
return b->data;
}
EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
void *dm_bufio_get_aux_data(struct dm_buffer *b)
{
return b + 1;
}
EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
{
return b->c;
}
EXPORT_SYMBOL_GPL(dm_bufio_get_client);
static enum it_action warn_leak(struct dm_buffer *b, void *context)
{
bool *warned = context;
WARN_ON(!(*warned));
*warned = true;
DMERR("leaked buffer %llx, hold count %u, list %d",
(unsigned long long)b->block, atomic_read(&b->hold_count), b->list_mode);
#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
stack_trace_print(b->stack_entries, b->stack_len, 1);
/* mark unclaimed to avoid WARN_ON at end of drop_buffers() */
atomic_set(&b->hold_count, 0);
#endif
return IT_NEXT;
}
static void drop_buffers(struct dm_bufio_client *c)
{
int i;
struct dm_buffer *b;
if (WARN_ON(dm_bufio_in_request()))
return; /* should never happen */
/*
* 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++) {
bool warned = false;
cache_iterate(&c->cache, i, warn_leak, &warned);
}
#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
while ((b = __get_unclaimed_buffer(c)))
__free_buffer_wake(b);
#endif
for (i = 0; i < LIST_SIZE; i++)
WARN_ON(cache_count(&c->cache, i));
dm_bufio_unlock(c);
}
static unsigned long get_retain_buffers(struct dm_bufio_client *c)
{
unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes);
if (likely(c->sectors_per_block_bits >= 0))
retain_bytes >>= c->sectors_per_block_bits + SECTOR_SHIFT;
else
retain_bytes /= c->block_size;
return retain_bytes;
}
static void __scan(struct dm_bufio_client *c)
{
int l;
struct dm_buffer *b;
unsigned long freed = 0;
unsigned long retain_target = get_retain_buffers(c);
unsigned long count = cache_total(&c->cache);
for (l = 0; l < LIST_SIZE; l++) {
while (true) {
if (count - freed <= retain_target)
atomic_long_set(&c->need_shrink, 0);
if (!atomic_long_read(&c->need_shrink))
break;
b = cache_evict(&c->cache, l,
l == LIST_CLEAN ? is_clean : is_dirty, c);
if (!b)
break;
__make_buffer_clean(b);
__free_buffer_wake(b);
atomic_long_dec(&c->need_shrink);
freed++;
cond_resched();
}
}
}
static void shrink_work(struct work_struct *w)
{
struct dm_bufio_client *c = container_of(w, struct dm_bufio_client, shrink_work);
dm_bufio_lock(c);
__scan(c);
dm_bufio_unlock(c);
}
static unsigned long dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
{
struct dm_bufio_client *c;
c = shrink->private_data;
atomic_long_add(sc->nr_to_scan, &c->need_shrink);
queue_work(dm_bufio_wq, &c->shrink_work);
return sc->nr_to_scan;
}
static unsigned long dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
{
struct dm_bufio_client *c = shrink->private_data;
unsigned long count = cache_total(&c->cache);
unsigned long retain_target = get_retain_buffers(c);
unsigned long queued_for_cleanup = atomic_long_read(&c->need_shrink);
if (unlikely(count < retain_target))
count = 0;
else
count -= retain_target;
if (unlikely(count < queued_for_cleanup))
count = 0;
else
count -= queued_for_cleanup;
return count;
}
/*
* Create the buffering interface
*/
struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned int block_size,
unsigned int reserved_buffers, unsigned int aux_size,
void (*alloc_callback)(struct dm_buffer *),
void (*write_callback)(struct dm_buffer *),
unsigned int flags)
{
int r;
unsigned int num_locks;
struct dm_bufio_client *c;
char slab_name[27];
if (!block_size || block_size & ((1 << SECTOR_SHIFT) - 1)) {
DMERR("%s: block size not specified or is not multiple of 512b", __func__);
r = -EINVAL;
goto bad_client;
}
num_locks = dm_num_hash_locks();
c = kzalloc(sizeof(*c) + (num_locks * sizeof(struct buffer_tree)), GFP_KERNEL);
if (!c) {
r = -ENOMEM;
goto bad_client;
}
cache_init(&c->cache, num_locks, (flags & DM_BUFIO_CLIENT_NO_SLEEP) != 0);
c->bdev = bdev;
c->block_size = block_size;
if (is_power_of_2(block_size))
c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT;
else
c->sectors_per_block_bits = -1;
c->alloc_callback = alloc_callback;
c->write_callback = write_callback;
if (flags & DM_BUFIO_CLIENT_NO_SLEEP) {
c->no_sleep = true;
static_branch_inc(&no_sleep_enabled);
}
mutex_init(&c->lock);
spin_lock_init(&c->spinlock);
INIT_LIST_HEAD(&c->reserved_buffers);
c->need_reserved_buffers = reserved_buffers;
dm_bufio_set_minimum_buffers(c, DM_BUFIO_MIN_BUFFERS);
init_waitqueue_head(&c->free_buffer_wait);
c->async_write_error = 0;
c->dm_io = dm_io_client_create();
if (IS_ERR(c->dm_io)) {
r = PTR_ERR(c->dm_io);
goto bad_dm_io;
}
if (block_size <= KMALLOC_MAX_SIZE &&
(block_size < PAGE_SIZE || !is_power_of_2(block_size))) {
unsigned int align = min(1U << __ffs(block_size), (unsigned int)PAGE_SIZE);
snprintf(slab_name, sizeof(slab_name), "dm_bufio_cache-%u", block_size);
c->slab_cache = kmem_cache_create(slab_name, block_size, align,
SLAB_RECLAIM_ACCOUNT, NULL);
if (!c->slab_cache) {
r = -ENOMEM;
goto bad;
}
}
if (aux_size)
snprintf(slab_name, sizeof(slab_name), "dm_bufio_buffer-%u", aux_size);
else
snprintf(slab_name, sizeof(slab_name), "dm_bufio_buffer");
c->slab_buffer = kmem_cache_create(slab_name, sizeof(struct dm_buffer) + aux_size,
0, SLAB_RECLAIM_ACCOUNT, NULL);
if (!c->slab_buffer) {
r = -ENOMEM;
goto bad;
}
while (c->need_reserved_buffers) {
struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
if (!b) {
r = -ENOMEM;
goto bad;
}
__free_buffer_wake(b);
}
INIT_WORK(&c->shrink_work, shrink_work);
atomic_long_set(&c->need_shrink, 0);
c->shrinker = shrinker_alloc(0, "dm-bufio:(%u:%u)",
MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));
if (!c->shrinker) {
r = -ENOMEM;
goto bad;
}
c->shrinker->count_objects = dm_bufio_shrink_count;
c->shrinker->scan_objects = dm_bufio_shrink_scan;
c->shrinker->seeks = 1;
c->shrinker->batch = 0;
c->shrinker->private_data = c;
shrinker_register(c->shrinker);
mutex_lock(&dm_bufio_clients_lock);
dm_bufio_client_count++;
list_add(&c->client_list, &dm_bufio_all_clients);
__cache_size_refresh();
mutex_unlock(&dm_bufio_clients_lock);
return c;
bad:
while (!list_empty(&c->reserved_buffers)) {
struct dm_buffer *b = list_to_buffer(c->reserved_buffers.next);
list_del(&b->lru.list);
free_buffer(b);
}
kmem_cache_destroy(c->slab_cache);
kmem_cache_destroy(c->slab_buffer);
dm_io_client_destroy(c->dm_io);
bad_dm_io:
mutex_destroy(&c->lock);
if (c->no_sleep)
static_branch_dec(&no_sleep_enabled);
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 int i;
drop_buffers(c);
shrinker_free(c->shrinker);
flush_work(&c->shrink_work);
mutex_lock(&dm_bufio_clients_lock);
list_del(&c->client_list);
dm_bufio_client_count--;
__cache_size_refresh();
mutex_unlock(&dm_bufio_clients_lock);
WARN_ON(c->need_reserved_buffers);
while (!list_empty(&c->reserved_buffers)) {
struct dm_buffer *b = list_to_buffer(c->reserved_buffers.next);
list_del(&b->lru.list);
free_buffer(b);
}
for (i = 0; i < LIST_SIZE; i++)
if (cache_count(&c->cache, i))
DMERR("leaked buffer count %d: %lu", i, cache_count(&c->cache, i));
for (i = 0; i < LIST_SIZE; i++)
WARN_ON(cache_count(&c->cache, i));
cache_destroy(&c->cache);
kmem_cache_destroy(c->slab_cache);
kmem_cache_destroy(c->slab_buffer);
dm_io_client_destroy(c->dm_io);
mutex_destroy(&c->lock);
if (c->no_sleep)
static_branch_dec(&no_sleep_enabled);
kfree(c);
}
EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
void dm_bufio_client_reset(struct dm_bufio_client *c)
{
drop_buffers(c);
flush_work(&c->shrink_work);
}
EXPORT_SYMBOL_GPL(dm_bufio_client_reset);
void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start)
{
c->start = start;
}
EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
/*--------------------------------------------------------------*/
static unsigned int get_max_age_hz(void)
{
unsigned int max_age = READ_ONCE(dm_bufio_max_age);
if (max_age > UINT_MAX / HZ)
max_age = UINT_MAX / HZ;
return max_age * HZ;
}
static bool older_than(struct dm_buffer *b, unsigned long age_hz)
{
return time_after_eq(jiffies, READ_ONCE(b->last_accessed) + age_hz);
}
struct evict_params {
gfp_t gfp;
unsigned long age_hz;
/*
* This gets updated with the largest last_accessed (ie. most
* recently used) of the evicted buffers. It will not be reinitialised
* by __evict_many(), so you can use it across multiple invocations.
*/
unsigned long last_accessed;
};
/*
* We may not be able to evict this buffer if IO pending or the client
* is still using it.
*
* 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 enum evict_result select_for_evict(struct dm_buffer *b, void *context)
{
struct evict_params *params = context;
if (!(params->gfp & __GFP_FS) ||
(static_branch_unlikely(&no_sleep_enabled) && b->c->no_sleep)) {
if (test_bit_acquire(B_READING, &b->state) ||
test_bit(B_WRITING, &b->state) ||
test_bit(B_DIRTY, &b->state))
return ER_DONT_EVICT;
}
return older_than(b, params->age_hz) ? ER_EVICT : ER_STOP;
}
static unsigned long __evict_many(struct dm_bufio_client *c,
struct evict_params *params,
int list_mode, unsigned long max_count)
{
unsigned long count;
unsigned long last_accessed;
struct dm_buffer *b;
for (count = 0; count < max_count; count++) {
b = cache_evict(&c->cache, list_mode, select_for_evict, params);
if (!b)
break;
last_accessed = READ_ONCE(b->last_accessed);
if (time_after_eq(params->last_accessed, last_accessed))
params->last_accessed = last_accessed;
__make_buffer_clean(b);
__free_buffer_wake(b);
cond_resched();
}
return count;
}
static void evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
{
struct evict_params params = {.gfp = 0, .age_hz = age_hz, .last_accessed = 0};
unsigned long retain = get_retain_buffers(c);
unsigned long count;
LIST_HEAD(write_list);
dm_bufio_lock(c);
__check_watermark(c, &write_list);
if (unlikely(!list_empty(&write_list))) {
dm_bufio_unlock(c);
__flush_write_list(&write_list);
dm_bufio_lock(c);
}
count = cache_total(&c->cache);
if (count > retain)
__evict_many(c, ¶ms, LIST_CLEAN, count - retain);
dm_bufio_unlock(c);
}
static void cleanup_old_buffers(void)
{
unsigned long max_age_hz = get_max_age_hz();
struct dm_bufio_client *c;
mutex_lock(&dm_bufio_clients_lock);
__cache_size_refresh();
list_for_each_entry(c, &dm_bufio_all_clients, client_list)
evict_old_buffers(c, max_age_hz);
mutex_unlock(&dm_bufio_clients_lock);
}
static void work_fn(struct work_struct *w)
{
cleanup_old_buffers();
queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
DM_BUFIO_WORK_TIMER_SECS * HZ);
}
/*--------------------------------------------------------------*/
/*
* Global cleanup tries to evict the oldest buffers from across _all_
* the clients. It does this by repeatedly evicting a few buffers from
* the client that holds the oldest buffer. It's approximate, but hopefully
* good enough.
*/
static struct dm_bufio_client *__pop_client(void)
{
struct list_head *h;
if (list_empty(&dm_bufio_all_clients))
return NULL;
h = dm_bufio_all_clients.next;
list_del(h);
return container_of(h, struct dm_bufio_client, client_list);
}
/*
* Inserts the client in the global client list based on its
* 'oldest_buffer' field.
*/
static void __insert_client(struct dm_bufio_client *new_client)
{
struct dm_bufio_client *c;
struct list_head *h = dm_bufio_all_clients.next;
while (h != &dm_bufio_all_clients) {
c = container_of(h, struct dm_bufio_client, client_list);
if (time_after_eq(c->oldest_buffer, new_client->oldest_buffer))
break;
h = h->next;
}
list_add_tail(&new_client->client_list, h);
}
static unsigned long __evict_a_few(unsigned long nr_buffers)
{
unsigned long count;
struct dm_bufio_client *c;
struct evict_params params = {
.gfp = GFP_KERNEL,
.age_hz = 0,
/* set to jiffies in case there are no buffers in this client */
.last_accessed = jiffies
};
c = __pop_client();
if (!c)
return 0;
dm_bufio_lock(c);
count = __evict_many(c, ¶ms, LIST_CLEAN, nr_buffers);
dm_bufio_unlock(c);
if (count)
c->oldest_buffer = params.last_accessed;
__insert_client(c);
return count;
}
static void check_watermarks(void)
{
LIST_HEAD(write_list);
struct dm_bufio_client *c;
mutex_lock(&dm_bufio_clients_lock);
list_for_each_entry(c, &dm_bufio_all_clients, client_list) {
dm_bufio_lock(c);
__check_watermark(c, &write_list);
dm_bufio_unlock(c);
}
mutex_unlock(&dm_bufio_clients_lock);
__flush_write_list(&write_list);
}
static void evict_old(void)
{
unsigned long threshold = dm_bufio_cache_size -
dm_bufio_cache_size / DM_BUFIO_LOW_WATERMARK_RATIO;
mutex_lock(&dm_bufio_clients_lock);
while (dm_bufio_current_allocated > threshold) {
if (!__evict_a_few(64))
break;
cond_resched();
}
mutex_unlock(&dm_bufio_clients_lock);
}
static void do_global_cleanup(struct work_struct *w)
{
check_watermarks();
evict_old();
}
/*
*--------------------------------------------------------------
* Module setup
*--------------------------------------------------------------
*/
/*
* This is called only once for the whole dm_bufio module.
* It initializes memory limit.
*/
static int __init dm_bufio_init(void)
{
__u64 mem;
dm_bufio_allocated_kmem_cache = 0;
dm_bufio_allocated_get_free_pages = 0;
dm_bufio_allocated_vmalloc = 0;
dm_bufio_current_allocated = 0;
mem = (__u64)mult_frac(totalram_pages() - totalhigh_pages(),
DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT;
if (mem > ULONG_MAX)
mem = ULONG_MAX;
#ifdef CONFIG_MMU
if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100))
mem = mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100);
#endif
dm_bufio_default_cache_size = mem;
mutex_lock(&dm_bufio_clients_lock);
__cache_size_refresh();
mutex_unlock(&dm_bufio_clients_lock);
dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0);
if (!dm_bufio_wq)
return -ENOMEM;
INIT_DELAYED_WORK(&dm_bufio_cleanup_old_work, work_fn);
INIT_WORK(&dm_bufio_replacement_work, do_global_cleanup);
queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
DM_BUFIO_WORK_TIMER_SECS * HZ);
return 0;
}
/*
* This is called once when unloading the dm_bufio module.
*/
static void __exit dm_bufio_exit(void)
{
int bug = 0;
cancel_delayed_work_sync(&dm_bufio_cleanup_old_work);
destroy_workqueue(dm_bufio_wq);
if (dm_bufio_client_count) {
DMCRIT("%s: dm_bufio_client_count leaked: %d",
__func__, dm_bufio_client_count);
bug = 1;
}
if (dm_bufio_current_allocated) {
DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
__func__, dm_bufio_current_allocated);
bug = 1;
}
if (dm_bufio_allocated_get_free_pages) {
DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
__func__, dm_bufio_allocated_get_free_pages);
bug = 1;
}
if (dm_bufio_allocated_vmalloc) {
DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
__func__, dm_bufio_allocated_vmalloc);
bug = 1;
}
WARN_ON(bug); /* leaks are not worth crashing the system */
}
module_init(dm_bufio_init)
module_exit(dm_bufio_exit)
module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, 0644);
MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
module_param_named(max_age_seconds, dm_bufio_max_age, uint, 0644);
MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, 0644);
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, 0644);
MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, 0444);
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, 0444);
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, 0444);
MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, 0444);
MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
MODULE_AUTHOR("Mikulas Patocka <[email protected]>");
MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
MODULE_LICENSE("GPL");
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