| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Mikulas Patocka | 6113 | 50.77% | 43 | 38.05% |
| Joe Thornber | 5228 | 43.42% | 9 | 7.96% |
| Mike Snitzer | 247 | 2.05% | 9 | 7.96% |
| Nathan Huckleberry | 61 | 0.51% | 2 | 1.77% |
| Qi Zheng | 59 | 0.49% | 1 | 0.88% |
| Heinz Mauelshagen | 48 | 0.40% | 6 | 5.31% |
| Christoph Hellwig | 42 | 0.35% | 6 | 5.31% |
| David Chinner | 42 | 0.35% | 1 | 0.88% |
| Darrick J. Wong | 23 | 0.19% | 1 | 0.88% |
| Bart Van Assche | 20 | 0.17% | 2 | 1.77% |
| Aliaksei Karaliou | 19 | 0.16% | 2 | 1.77% |
| Li Lingfeng | 19 | 0.16% | 1 | 0.88% |
| Eric Biggers | 17 | 0.14% | 1 | 0.88% |
| Thomas Gleixner | 15 | 0.12% | 1 | 0.88% |
| Suren Baghdasaryan | 11 | 0.09% | 1 | 0.88% |
| Kent Overstreet | 9 | 0.07% | 2 | 1.77% |
| Peter Zijlstra | 8 | 0.07% | 2 | 1.77% |
| Michael Christie | 7 | 0.06% | 2 | 1.77% |
| Neil Brown | 6 | 0.05% | 1 | 0.88% |
| Bhaktipriya Shridhar | 5 | 0.04% | 1 | 0.88% |
| Asaf Vertz | 5 | 0.04% | 1 | 0.88% |
| Arnd Bergmann | 4 | 0.03% | 1 | 0.88% |
| Stephen Rothwell | 3 | 0.02% | 1 | 0.88% |
| Ingo Molnar | 3 | 0.02% | 1 | 0.88% |
| Roman Gushchin | 3 | 0.02% | 1 | 0.88% |
| Mark Rutland | 3 | 0.02% | 1 | 0.88% |
| Jan Kara | 2 | 0.02% | 1 | 0.88% |
| Arun K S | 2 | 0.02% | 1 | 0.88% |
| Wang Sheng-Hui | 2 | 0.02% | 1 | 0.88% |
| Lei Ming | 2 | 0.02% | 1 | 0.88% |
| Anup Limbu | 2 | 0.02% | 1 | 0.88% |
| Doug Anderson | 2 | 0.02% | 1 | 0.88% |
| Dan Carpenter | 2 | 0.02% | 1 | 0.88% |
| Jens Axboe | 1 | 0.01% | 1 | 0.88% |
| Kirill A. Shutemov | 1 | 0.01% | 1 | 0.88% |
| Greg Thelen | 1 | 0.01% | 1 | 0.88% |
| Davidlohr Bueso A | 1 | 0.01% | 1 | 0.88% |
| Zhihao Cheng | 1 | 0.01% | 1 | 0.88% |
| Al Viro | 1 | 0.01% | 1 | 0.88% |
| Total | 12040 | 113 |
// 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 = 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 <dm-devel@redhat.com>"); MODULE_DESCRIPTION(DM_NAME " buffered I/O library"); MODULE_LICENSE("GPL");
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