diff options
Diffstat (limited to 'drivers/md/dm-bufio.c')
| -rw-r--r-- | drivers/md/dm-bufio.c | 2967 |
1 files changed, 2967 insertions, 0 deletions
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c new file mode 100644 index 0000000000..486e1180cc --- /dev/null +++ b/drivers/md/dm-bufio.c @@ -0,0 +1,2967 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2009-2011 Red Hat, Inc. + * + * Author: Mikulas Patocka <mpatocka@redhat.com> + * + * This file is released under the GPL. + */ + +#include <linux/dm-bufio.h> + +#include <linux/device-mapper.h> +#include <linux/dm-io.h> +#include <linux/slab.h> +#include <linux/sched/mm.h> +#include <linux/jiffies.h> +#include <linux/vmalloc.h> +#include <linux/shrinker.h> +#include <linux/module.h> +#include <linux/rbtree.h> +#include <linux/stacktrace.h> +#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); + + if (!le) + return NULL; + + 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_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) +{ + 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); + 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) +{ + 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); + 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; + + 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, + 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); + else + use_dmio(b, op, sector, n_sectors, offset); +} + +/* + *-------------------------------------------------------------- + * Writing dirty buffers + *-------------------------------------------------------------- + */ + +/* + * The endio routine for write. + * + * Set the error, clear B_WRITING bit and wake anyone who was waiting on + * it. + */ +static void write_endio(struct dm_buffer *b, blk_status_t status) +{ + b->write_error = status; + if (unlikely(status)) { + struct dm_bufio_client *c = b->c; + + (void)cmpxchg(&c->async_write_error, 0, + blk_status_to_errno(status)); + } + + BUG_ON(!test_bit(B_WRITING, &b->state)); + + smp_mb__before_atomic(); + clear_bit(B_WRITING, &b->state); + smp_mb__after_atomic(); + + wake_up_bit(&b->state, B_WRITING); +} + +/* + * Initiate a write on a dirty buffer, but don't wait for it. + * + * - If the buffer is not dirty, exit. + * - If there some previous write going on, wait for it to finish (we can't + * have two writes on the same buffer simultaneously). + * - Submit our write and don't wait on it. We set B_WRITING indicating + * that there is a write in progress. + */ +static void __write_dirty_buffer(struct dm_buffer *b, + struct list_head *write_list) +{ + if (!test_bit(B_DIRTY, &b->state)) + return; + + clear_bit(B_DIRTY, &b->state); + wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE); + + b->write_start = b->dirty_start; + b->write_end = b->dirty_end; + + if (!write_list) + submit_io(b, REQ_OP_WRITE, write_endio); + else + list_add_tail(&b->write_list, write_list); +} + +static void __flush_write_list(struct list_head *write_list) +{ + struct blk_plug plug; + + blk_start_plug(&plug); + while (!list_empty(write_list)) { + struct dm_buffer *b = + list_entry(write_list->next, struct dm_buffer, write_list); + list_del(&b->write_list); + submit_io(b, REQ_OP_WRITE, write_endio); + cond_resched(); + } + blk_finish_plug(&plug); +} + +/* + * Wait until any activity on the buffer finishes. Possibly write the + * buffer if it is dirty. When this function finishes, there is no I/O + * running on the buffer and the buffer is not dirty. + */ +static void __make_buffer_clean(struct dm_buffer *b) +{ + BUG_ON(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) +{ + 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, 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); +} +EXPORT_SYMBOL_GPL(dm_bufio_get); + +void *dm_bufio_read(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_READ, bp); +} +EXPORT_SYMBOL_GPL(dm_bufio_read); + +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); +} +EXPORT_SYMBOL_GPL(dm_bufio_new); + +void dm_bufio_prefetch(struct dm_bufio_client *c, + sector_t block, unsigned int n_blocks) +{ + 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, read_endio); + dm_bufio_release(b); + + cond_resched(); + + if (!n_blocks) + goto flush_plug; + dm_bufio_lock(c); + } + dm_bufio_unlock(c); + } + +flush_plug: + blk_finish_plug(&plug); +} +EXPORT_SYMBOL_GPL(dm_bufio_prefetch); + +void dm_bufio_release(struct dm_buffer *b) +{ + struct dm_bufio_client *c = b->c; + + /* + * 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); +} +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); +} +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 = container_of(shrink, struct dm_bufio_client, shrinker); + 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 = container_of(shrink, struct dm_bufio_client, shrinker); + 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.count_objects = dm_bufio_shrink_count; + c->shrinker.scan_objects = dm_bufio_shrink_scan; + c->shrinker.seeks = 1; + c->shrinker.batch = 0; + r = register_shrinker(&c->shrinker, "dm-bufio:(%u:%u)", + MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev)); + if (r) + goto bad; + + mutex_lock(&dm_bufio_clients_lock); + dm_bufio_client_count++; + list_add(&c->client_list, &dm_bufio_all_clients); + __cache_size_refresh(); + mutex_unlock(&dm_bufio_clients_lock); + + return c; + +bad: + while (!list_empty(&c->reserved_buffers)) { + struct dm_buffer *b = list_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); + + unregister_shrinker(&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 <dm-devel@redhat.com>"); +MODULE_DESCRIPTION(DM_NAME " buffered I/O library"); +MODULE_LICENSE("GPL"); |