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Diffstat (limited to 'drivers/md/bcache/bcache.h')
| -rw-r--r-- | drivers/md/bcache/bcache.h | 1232 |
1 files changed, 1232 insertions, 0 deletions
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h new file mode 100644 index 000000000000..d01a553f63f3 --- /dev/null +++ b/drivers/md/bcache/bcache.h @@ -0,0 +1,1232 @@ +#ifndef _BCACHE_H +#define _BCACHE_H + +/* + * SOME HIGH LEVEL CODE DOCUMENTATION: + * + * Bcache mostly works with cache sets, cache devices, and backing devices. + * + * Support for multiple cache devices hasn't quite been finished off yet, but + * it's about 95% plumbed through. A cache set and its cache devices is sort of + * like a md raid array and its component devices. Most of the code doesn't care + * about individual cache devices, the main abstraction is the cache set. + * + * Multiple cache devices is intended to give us the ability to mirror dirty + * cached data and metadata, without mirroring clean cached data. + * + * Backing devices are different, in that they have a lifetime independent of a + * cache set. When you register a newly formatted backing device it'll come up + * in passthrough mode, and then you can attach and detach a backing device from + * a cache set at runtime - while it's mounted and in use. Detaching implicitly + * invalidates any cached data for that backing device. + * + * A cache set can have multiple (many) backing devices attached to it. + * + * There's also flash only volumes - this is the reason for the distinction + * between struct cached_dev and struct bcache_device. A flash only volume + * works much like a bcache device that has a backing device, except the + * "cached" data is always dirty. The end result is that we get thin + * provisioning with very little additional code. + * + * Flash only volumes work but they're not production ready because the moving + * garbage collector needs more work. More on that later. + * + * BUCKETS/ALLOCATION: + * + * Bcache is primarily designed for caching, which means that in normal + * operation all of our available space will be allocated. Thus, we need an + * efficient way of deleting things from the cache so we can write new things to + * it. + * + * To do this, we first divide the cache device up into buckets. A bucket is the + * unit of allocation; they're typically around 1 mb - anywhere from 128k to 2M+ + * works efficiently. + * + * Each bucket has a 16 bit priority, and an 8 bit generation associated with + * it. The gens and priorities for all the buckets are stored contiguously and + * packed on disk (in a linked list of buckets - aside from the superblock, all + * of bcache's metadata is stored in buckets). + * + * The priority is used to implement an LRU. We reset a bucket's priority when + * we allocate it or on cache it, and every so often we decrement the priority + * of each bucket. It could be used to implement something more sophisticated, + * if anyone ever gets around to it. + * + * The generation is used for invalidating buckets. Each pointer also has an 8 + * bit generation embedded in it; for a pointer to be considered valid, its gen + * must match the gen of the bucket it points into. Thus, to reuse a bucket all + * we have to do is increment its gen (and write its new gen to disk; we batch + * this up). + * + * Bcache is entirely COW - we never write twice to a bucket, even buckets that + * contain metadata (including btree nodes). + * + * THE BTREE: + * + * Bcache is in large part design around the btree. + * + * At a high level, the btree is just an index of key -> ptr tuples. + * + * Keys represent extents, and thus have a size field. Keys also have a variable + * number of pointers attached to them (potentially zero, which is handy for + * invalidating the cache). + * + * The key itself is an inode:offset pair. The inode number corresponds to a + * backing device or a flash only volume. The offset is the ending offset of the + * extent within the inode - not the starting offset; this makes lookups + * slightly more convenient. + * + * Pointers contain the cache device id, the offset on that device, and an 8 bit + * generation number. More on the gen later. + * + * Index lookups are not fully abstracted - cache lookups in particular are + * still somewhat mixed in with the btree code, but things are headed in that + * direction. + * + * Updates are fairly well abstracted, though. There are two different ways of + * updating the btree; insert and replace. + * + * BTREE_INSERT will just take a list of keys and insert them into the btree - + * overwriting (possibly only partially) any extents they overlap with. This is + * used to update the index after a write. + * + * BTREE_REPLACE is really cmpxchg(); it inserts a key into the btree iff it is + * overwriting a key that matches another given key. This is used for inserting + * data into the cache after a cache miss, and for background writeback, and for + * the moving garbage collector. + * + * There is no "delete" operation; deleting things from the index is + * accomplished by either by invalidating pointers (by incrementing a bucket's + * gen) or by inserting a key with 0 pointers - which will overwrite anything + * previously present at that location in the index. + * + * This means that there are always stale/invalid keys in the btree. They're + * filtered out by the code that iterates through a btree node, and removed when + * a btree node is rewritten. + * + * BTREE NODES: + * + * Our unit of allocation is a bucket, and we we can't arbitrarily allocate and + * free smaller than a bucket - so, that's how big our btree nodes are. + * + * (If buckets are really big we'll only use part of the bucket for a btree node + * - no less than 1/4th - but a bucket still contains no more than a single + * btree node. I'd actually like to change this, but for now we rely on the + * bucket's gen for deleting btree nodes when we rewrite/split a node.) + * + * Anyways, btree nodes are big - big enough to be inefficient with a textbook + * btree implementation. + * + * The way this is solved is that btree nodes are internally log structured; we + * can append new keys to an existing btree node without rewriting it. This + * means each set of keys we write is sorted, but the node is not. + * + * We maintain this log structure in memory - keeping 1Mb of keys sorted would + * be expensive, and we have to distinguish between the keys we have written and + * the keys we haven't. So to do a lookup in a btree node, we have to search + * each sorted set. But we do merge written sets together lazily, so the cost of + * these extra searches is quite low (normally most of the keys in a btree node + * will be in one big set, and then there'll be one or two sets that are much + * smaller). + * + * This log structure makes bcache's btree more of a hybrid between a + * conventional btree and a compacting data structure, with some of the + * advantages of both. + * + * GARBAGE COLLECTION: + * + * We can't just invalidate any bucket - it might contain dirty data or + * metadata. If it once contained dirty data, other writes might overwrite it + * later, leaving no valid pointers into that bucket in the index. + * + * Thus, the primary purpose of garbage collection is to find buckets to reuse. + * It also counts how much valid data it each bucket currently contains, so that + * allocation can reuse buckets sooner when they've been mostly overwritten. + * + * It also does some things that are really internal to the btree + * implementation. If a btree node contains pointers that are stale by more than + * some threshold, it rewrites the btree node to avoid the bucket's generation + * wrapping around. It also merges adjacent btree nodes if they're empty enough. + * + * THE JOURNAL: + * + * Bcache's journal is not necessary for consistency; we always strictly + * order metadata writes so that the btree and everything else is consistent on + * disk in the event of an unclean shutdown, and in fact bcache had writeback + * caching (with recovery from unclean shutdown) before journalling was + * implemented. + * + * Rather, the journal is purely a performance optimization; we can't complete a + * write until we've updated the index on disk, otherwise the cache would be + * inconsistent in the event of an unclean shutdown. This means that without the + * journal, on random write workloads we constantly have to update all the leaf + * nodes in the btree, and those writes will be mostly empty (appending at most + * a few keys each) - highly inefficient in terms of amount of metadata writes, + * and it puts more strain on the various btree resorting/compacting code. + * + * The journal is just a log of keys we've inserted; on startup we just reinsert + * all the keys in the open journal entries. That means that when we're updating + * a node in the btree, we can wait until a 4k block of keys fills up before + * writing them out. + * + * For simplicity, we only journal updates to leaf nodes; updates to parent + * nodes are rare enough (since our leaf nodes are huge) that it wasn't worth + * the complexity to deal with journalling them (in particular, journal replay) + * - updates to non leaf nodes just happen synchronously (see btree_split()). + */ + +#define pr_fmt(fmt) "bcache: %s() " fmt "\n", __func__ + +#include <linux/bio.h> +#include <linux/blktrace_api.h> +#include <linux/kobject.h> +#include <linux/list.h> +#include <linux/mutex.h> +#include <linux/rbtree.h> +#include <linux/rwsem.h> +#include <linux/types.h> +#include <linux/workqueue.h> + +#include "util.h" +#include "closure.h" + +struct bucket { + atomic_t pin; + uint16_t prio; + uint8_t gen; + uint8_t disk_gen; + uint8_t last_gc; /* Most out of date gen in the btree */ + uint8_t gc_gen; + uint16_t gc_mark; +}; + +/* + * I'd use bitfields for these, but I don't trust the compiler not to screw me + * as multiple threads touch struct bucket without locking + */ + +BITMASK(GC_MARK, struct bucket, gc_mark, 0, 2); +#define GC_MARK_RECLAIMABLE 0 +#define GC_MARK_DIRTY 1 +#define GC_MARK_METADATA 2 +BITMASK(GC_SECTORS_USED, struct bucket, gc_mark, 2, 14); + +struct bkey { + uint64_t high; + uint64_t low; + uint64_t ptr[]; +}; + +/* Enough for a key with 6 pointers */ +#define BKEY_PAD 8 + +#define BKEY_PADDED(key) \ + union { struct bkey key; uint64_t key ## _pad[BKEY_PAD]; } + +/* Version 1: Backing device + * Version 2: Seed pointer into btree node checksum + * Version 3: New UUID format + */ +#define BCACHE_SB_VERSION 3 + +#define SB_SECTOR 8 +#define SB_SIZE 4096 +#define SB_LABEL_SIZE 32 +#define SB_JOURNAL_BUCKETS 256U +/* SB_JOURNAL_BUCKETS must be divisible by BITS_PER_LONG */ +#define MAX_CACHES_PER_SET 8 + +#define BDEV_DATA_START 16 /* sectors */ + +struct cache_sb { + uint64_t csum; + uint64_t offset; /* sector where this sb was written */ + uint64_t version; +#define CACHE_BACKING_DEV 1 + + uint8_t magic[16]; + + uint8_t uuid[16]; + union { + uint8_t set_uuid[16]; + uint64_t set_magic; + }; + uint8_t label[SB_LABEL_SIZE]; + + uint64_t flags; + uint64_t seq; + uint64_t pad[8]; + + uint64_t nbuckets; /* device size */ + uint16_t block_size; /* sectors */ + uint16_t bucket_size; /* sectors */ + + uint16_t nr_in_set; + uint16_t nr_this_dev; + + uint32_t last_mount; /* time_t */ + + uint16_t first_bucket; + union { + uint16_t njournal_buckets; + uint16_t keys; + }; + uint64_t d[SB_JOURNAL_BUCKETS]; /* journal buckets */ +}; + +BITMASK(CACHE_SYNC, struct cache_sb, flags, 0, 1); +BITMASK(CACHE_DISCARD, struct cache_sb, flags, 1, 1); +BITMASK(CACHE_REPLACEMENT, struct cache_sb, flags, 2, 3); +#define CACHE_REPLACEMENT_LRU 0U +#define CACHE_REPLACEMENT_FIFO 1U +#define CACHE_REPLACEMENT_RANDOM 2U + +BITMASK(BDEV_CACHE_MODE, struct cache_sb, flags, 0, 4); +#define CACHE_MODE_WRITETHROUGH 0U +#define CACHE_MODE_WRITEBACK 1U +#define CACHE_MODE_WRITEAROUND 2U +#define CACHE_MODE_NONE 3U +BITMASK(BDEV_STATE, struct cache_sb, flags, 61, 2); +#define BDEV_STATE_NONE 0U +#define BDEV_STATE_CLEAN 1U +#define BDEV_STATE_DIRTY 2U +#define BDEV_STATE_STALE 3U + +/* Version 1: Seed pointer into btree node checksum + */ +#define BCACHE_BSET_VERSION 1 + +/* + * This is the on disk format for btree nodes - a btree node on disk is a list + * of these; within each set the keys are sorted + */ +struct bset { + uint64_t csum; + uint64_t magic; + uint64_t seq; + uint32_t version; + uint32_t keys; + + union { + struct bkey start[0]; + uint64_t d[0]; + }; +}; + +/* + * On disk format for priorities and gens - see super.c near prio_write() for + * more. + */ +struct prio_set { + uint64_t csum; + uint64_t magic; + uint64_t seq; + uint32_t version; + uint32_t pad; + + uint64_t next_bucket; + + struct bucket_disk { + uint16_t prio; + uint8_t gen; + } __attribute((packed)) data[]; +}; + +struct uuid_entry { + union { + struct { + uint8_t uuid[16]; + uint8_t label[32]; + uint32_t first_reg; + uint32_t last_reg; + uint32_t invalidated; + + uint32_t flags; + /* Size of flash only volumes */ + uint64_t sectors; + }; + + uint8_t pad[128]; + }; +}; + +BITMASK(UUID_FLASH_ONLY, struct uuid_entry, flags, 0, 1); + +#include "journal.h" +#include "stats.h" +struct search; +struct btree; +struct keybuf; + +struct keybuf_key { + struct rb_node node; + BKEY_PADDED(key); + void *private; +}; + +typedef bool (keybuf_pred_fn)(struct keybuf *, struct bkey *); + +struct keybuf { + keybuf_pred_fn *key_predicate; + + struct bkey last_scanned; + spinlock_t lock; + + /* + * Beginning and end of range in rb tree - so that we can skip taking + * lock and checking the rb tree when we need to check for overlapping + * keys. + */ + struct bkey start; + struct bkey end; + + struct rb_root keys; + +#define KEYBUF_NR 100 + DECLARE_ARRAY_ALLOCATOR(struct keybuf_key, freelist, KEYBUF_NR); +}; + +struct bio_split_pool { + struct bio_set *bio_split; + mempool_t *bio_split_hook; +}; + +struct bio_split_hook { + struct closure cl; + struct bio_split_pool *p; + struct bio *bio; + bio_end_io_t *bi_end_io; + void *bi_private; +}; + +struct bcache_device { + struct closure cl; + + struct kobject kobj; + + struct cache_set *c; + unsigned id; +#define BCACHEDEVNAME_SIZE 12 + char name[BCACHEDEVNAME_SIZE]; + + struct gendisk *disk; + + /* If nonzero, we're closing */ + atomic_t closing; + + /* If nonzero, we're detaching/unregistering from cache set */ + atomic_t detaching; + + atomic_long_t sectors_dirty; + unsigned long sectors_dirty_gc; + unsigned long sectors_dirty_last; + long sectors_dirty_derivative; + + mempool_t *unaligned_bvec; + struct bio_set *bio_split; + + unsigned data_csum:1; + + int (*cache_miss)(struct btree *, struct search *, + struct bio *, unsigned); + int (*ioctl) (struct bcache_device *, fmode_t, unsigned, unsigned long); + + struct bio_split_pool bio_split_hook; +}; + +struct io { + /* Used to track sequential IO so it can be skipped */ + struct hlist_node hash; + struct list_head lru; + + unsigned long jiffies; + unsigned sequential; + sector_t last; +}; + +struct cached_dev { + struct list_head list; + struct bcache_device disk; + struct block_device *bdev; + + struct cache_sb sb; + struct bio sb_bio; + struct bio_vec sb_bv[1]; + struct closure_with_waitlist sb_write; + + /* Refcount on the cache set. Always nonzero when we're caching. */ + atomic_t count; + struct work_struct detach; + + /* + * Device might not be running if it's dirty and the cache set hasn't + * showed up yet. + */ + atomic_t running; + + /* + * Writes take a shared lock from start to finish; scanning for dirty + * data to refill the rb tree requires an exclusive lock. + */ + struct rw_semaphore writeback_lock; + + /* + * Nonzero, and writeback has a refcount (d->count), iff there is dirty + * data in the cache. Protected by writeback_lock; must have an + * shared lock to set and exclusive lock to clear. + */ + atomic_t has_dirty; + + struct ratelimit writeback_rate; + struct delayed_work writeback_rate_update; + + /* + * Internal to the writeback code, so read_dirty() can keep track of + * where it's at. + */ + sector_t last_read; + + /* Number of writeback bios in flight */ + atomic_t in_flight; + struct closure_with_timer writeback; + struct closure_waitlist writeback_wait; + + struct keybuf writeback_keys; + + /* For tracking sequential IO */ +#define RECENT_IO_BITS 7 +#define RECENT_IO (1 << RECENT_IO_BITS) + struct io io[RECENT_IO]; + struct hlist_head io_hash[RECENT_IO + 1]; + struct list_head io_lru; + spinlock_t io_lock; + + struct cache_accounting accounting; + + /* The rest of this all shows up in sysfs */ + unsigned sequential_cutoff; + unsigned readahead; + + unsigned sequential_merge:1; + unsigned verify:1; + + unsigned writeback_metadata:1; + unsigned writeback_running:1; + unsigned char writeback_percent; + unsigned writeback_delay; + + int writeback_rate_change; + int64_t writeback_rate_derivative; + uint64_t writeback_rate_target; + + unsigned writeback_rate_update_seconds; + unsigned writeback_rate_d_term; + unsigned writeback_rate_p_term_inverse; + unsigned writeback_rate_d_smooth; +}; + +enum alloc_watermarks { + WATERMARK_PRIO, + WATERMARK_METADATA, + WATERMARK_MOVINGGC, + WATERMARK_NONE, + WATERMARK_MAX +}; + +struct cache { + struct cache_set *set; + struct cache_sb sb; + struct bio sb_bio; + struct bio_vec sb_bv[1]; + + struct kobject kobj; + struct block_device *bdev; + + unsigned watermark[WATERMARK_MAX]; + + struct closure alloc; + struct workqueue_struct *alloc_workqueue; + + struct closure prio; + struct prio_set *disk_buckets; + + /* + * When allocating new buckets, prio_write() gets first dibs - since we + * may not be allocate at all without writing priorities and gens. + * prio_buckets[] contains the last buckets we wrote priorities to (so + * gc can mark them as metadata), prio_next[] contains the buckets + * allocated for the next prio write. + */ + uint64_t *prio_buckets; + uint64_t *prio_last_buckets; + + /* + * free: Buckets that are ready to be used + * + * free_inc: Incoming buckets - these are buckets that currently have + * cached data in them, and we can't reuse them until after we write + * their new gen to disk. After prio_write() finishes writing the new + * gens/prios, they'll be moved to the free list (and possibly discarded + * in the process) + * + * unused: GC found nothing pointing into these buckets (possibly + * because all the data they contained was overwritten), so we only + * need to discard them before they can be moved to the free list. + */ + DECLARE_FIFO(long, free); + DECLARE_FIFO(long, free_inc); + DECLARE_FIFO(long, unused); + + size_t fifo_last_bucket; + + /* Allocation stuff: */ + struct bucket *buckets; + + DECLARE_HEAP(struct bucket *, heap); + + /* + * max(gen - disk_gen) for all buckets. When it gets too big we have to + * call prio_write() to keep gens from wrapping. + */ + uint8_t need_save_prio; + unsigned gc_move_threshold; + + /* + * If nonzero, we know we aren't going to find any buckets to invalidate + * until a gc finishes - otherwise we could pointlessly burn a ton of + * cpu + */ + unsigned invalidate_needs_gc:1; + + bool discard; /* Get rid of? */ + + /* + * We preallocate structs for issuing discards to buckets, and keep them + * on this list when they're not in use; do_discard() issues discards + * whenever there's work to do and is called by free_some_buckets() and + * when a discard finishes. + */ + atomic_t discards_in_flight; + struct list_head discards; + + struct journal_device journal; + + /* The rest of this all shows up in sysfs */ +#define IO_ERROR_SHIFT 20 + atomic_t io_errors; + atomic_t io_count; + + atomic_long_t meta_sectors_written; + atomic_long_t btree_sectors_written; + atomic_long_t sectors_written; + + struct bio_split_pool bio_split_hook; +}; + +struct gc_stat { + size_t nodes; + size_t key_bytes; + + size_t nkeys; + uint64_t data; /* sectors */ + uint64_t dirty; /* sectors */ + unsigned in_use; /* percent */ +}; + +/* + * Flag bits, for how the cache set is shutting down, and what phase it's at: + * + * CACHE_SET_UNREGISTERING means we're not just shutting down, we're detaching + * all the backing devices first (their cached data gets invalidated, and they + * won't automatically reattach). + * + * CACHE_SET_STOPPING always gets set first when we're closing down a cache set; + * we'll continue to run normally for awhile with CACHE_SET_STOPPING set (i.e. + * flushing dirty data). + * + * CACHE_SET_STOPPING_2 gets set at the last phase, when it's time to shut down the + * allocation thread. + */ +#define CACHE_SET_UNREGISTERING 0 +#define CACHE_SET_STOPPING 1 +#define CACHE_SET_STOPPING_2 2 + +struct cache_set { + struct closure cl; + + struct list_head list; + struct kobject kobj; + struct kobject internal; + struct dentry *debug; + struct cache_accounting accounting; + + unsigned long flags; + + struct cache_sb sb; + + struct cache *cache[MAX_CACHES_PER_SET]; + struct cache *cache_by_alloc[MAX_CACHES_PER_SET]; + int caches_loaded; + + struct bcache_device **devices; + struct list_head cached_devs; + uint64_t cached_dev_sectors; + struct closure caching; + + struct closure_with_waitlist sb_write; + + mempool_t *search; + mempool_t *bio_meta; + struct bio_set *bio_split; + + /* For the btree cache */ + struct shrinker shrink; + + /* For the allocator itself */ + wait_queue_head_t alloc_wait; + + /* For the btree cache and anything allocation related */ + struct mutex bucket_lock; + + /* log2(bucket_size), in sectors */ + unsigned short bucket_bits; + + /* log2(block_size), in sectors */ + unsigned short block_bits; + + /* + * Default number of pages for a new btree node - may be less than a + * full bucket + */ + unsigned btree_pages; + + /* + * Lists of struct btrees; lru is the list for structs that have memory + * allocated for actual btree node, freed is for structs that do not. + * + * We never free a struct btree, except on shutdown - we just put it on + * the btree_cache_freed list and reuse it later. This simplifies the + * code, and it doesn't cost us much memory as the memory usage is + * dominated by buffers that hold the actual btree node data and those + * can be freed - and the number of struct btrees allocated is + * effectively bounded. + * + * btree_cache_freeable effectively is a small cache - we use it because + * high order page allocations can be rather expensive, and it's quite + * common to delete and allocate btree nodes in quick succession. It + * should never grow past ~2-3 nodes in practice. + */ + struct list_head btree_cache; + struct list_head btree_cache_freeable; + struct list_head btree_cache_freed; + + /* Number of elements in btree_cache + btree_cache_freeable lists */ + unsigned bucket_cache_used; + + /* + * If we need to allocate memory for a new btree node and that + * allocation fails, we can cannibalize another node in the btree cache + * to satisfy the allocation. However, only one thread can be doing this + * at a time, for obvious reasons - try_harder and try_wait are + * basically a lock for this that we can wait on asynchronously. The + * btree_root() macro releases the lock when it returns. + */ + struct closure *try_harder; + struct closure_waitlist try_wait; + uint64_t try_harder_start; + + /* + * When we free a btree node, we increment the gen of the bucket the + * node is in - but we can't rewrite the prios and gens until we + * finished whatever it is we were doing, otherwise after a crash the + * btree node would be freed but for say a split, we might not have the + * pointers to the new nodes inserted into the btree yet. + * + * This is a refcount that blocks prio_write() until the new keys are + * written. + */ + atomic_t prio_blocked; + struct closure_waitlist bucket_wait; + + /* + * For any bio we don't skip we subtract the number of sectors from + * rescale; when it hits 0 we rescale all the bucket priorities. + */ + atomic_t rescale; + /* + * When we invalidate buckets, we use both the priority and the amount + * of good data to determine which buckets to reuse first - to weight + * those together consistently we keep track of the smallest nonzero + * priority of any bucket. + */ + uint16_t min_prio; + + /* + * max(gen - gc_gen) for all buckets. When it gets too big we have to gc + * to keep gens from wrapping around. + */ + uint8_t need_gc; + struct gc_stat gc_stats; + size_t nbuckets; + + struct closure_with_waitlist gc; + /* Where in the btree gc currently is */ + struct bkey gc_done; + + /* + * The allocation code needs gc_mark in struct bucket to be correct, but + * it's not while a gc is in progress. Protected by bucket_lock. + */ + int gc_mark_valid; + + /* Counts how many sectors bio_insert has added to the cache */ + atomic_t sectors_to_gc; + + struct closure moving_gc; + struct closure_waitlist moving_gc_wait; + struct keybuf moving_gc_keys; + /* Number of moving GC bios in flight */ + atomic_t in_flight; + + struct btree *root; + +#ifdef CONFIG_BCACHE_DEBUG + struct btree *verify_data; + struct mutex verify_lock; +#endif + + unsigned nr_uuids; + struct uuid_entry *uuids; + BKEY_PADDED(uuid_bucket); + struct closure_with_waitlist uuid_write; + + /* + * A btree node on disk could have too many bsets for an iterator to fit + * on the stack - this is a single element mempool for btree_read_work() + */ + struct mutex fill_lock; + struct btree_iter *fill_iter; + + /* + * btree_sort() is a merge sort and requires temporary space - single + * element mempool + */ + struct mutex sort_lock; + struct bset *sort; + + /* List of buckets we're currently writing data to */ + struct list_head data_buckets; + spinlock_t data_bucket_lock; + + struct journal journal; + +#define CONGESTED_MAX 1024 + unsigned congested_last_us; + atomic_t congested; + + /* The rest of this all shows up in sysfs */ + unsigned congested_read_threshold_us; + unsigned congested_write_threshold_us; + + spinlock_t sort_time_lock; + struct time_stats sort_time; + struct time_stats btree_gc_time; + struct time_stats btree_split_time; + spinlock_t btree_read_time_lock; + struct time_stats btree_read_time; + struct time_stats try_harder_time; + + atomic_long_t cache_read_races; + atomic_long_t writeback_keys_done; + atomic_long_t writeback_keys_failed; + unsigned error_limit; + unsigned error_decay; + unsigned short journal_delay_ms; + unsigned verify:1; + unsigned key_merging_disabled:1; + unsigned gc_always_rewrite:1; + unsigned shrinker_disabled:1; + unsigned copy_gc_enabled:1; + +#define BUCKET_HASH_BITS 12 + struct hlist_head bucket_hash[1 << BUCKET_HASH_BITS]; +}; + +static inline bool key_merging_disabled(struct cache_set *c) +{ +#ifdef CONFIG_BCACHE_DEBUG + return c->key_merging_disabled; +#else + return 0; +#endif +} + +struct bbio { + unsigned submit_time_us; + union { + struct bkey key; + uint64_t _pad[3]; + /* + * We only need pad = 3 here because we only ever carry around a + * single pointer - i.e. the pointer we're doing io to/from. + */ + }; + struct bio bio; +}; + +static inline unsigned local_clock_us(void) +{ + return local_clock() >> 10; +} + +#define MAX_BSETS 4U + +#define BTREE_PRIO USHRT_MAX +#define INITIAL_PRIO 32768 + +#define btree_bytes(c) ((c)->btree_pages * PAGE_SIZE) +#define btree_blocks(b) \ + ((unsigned) (KEY_SIZE(&b->key) >> (b)->c->block_bits)) + +#define btree_default_blocks(c) \ + ((unsigned) ((PAGE_SECTORS * (c)->btree_pages) >> (c)->block_bits)) + +#define bucket_pages(c) ((c)->sb.bucket_size / PAGE_SECTORS) +#define bucket_bytes(c) ((c)->sb.bucket_size << 9) +#define block_bytes(c) ((c)->sb.block_size << 9) + +#define __set_bytes(i, k) (sizeof(*(i)) + (k) * sizeof(uint64_t)) +#define set_bytes(i) __set_bytes(i, i->keys) + +#define __set_blocks(i, k, c) DIV_ROUND_UP(__set_bytes(i, k), block_bytes(c)) +#define set_blocks(i, c) __set_blocks(i, (i)->keys, c) + +#define node(i, j) ((struct bkey *) ((i)->d + (j))) +#define end(i) node(i, (i)->keys) + +#define index(i, b) \ + ((size_t) (((void *) i - (void *) (b)->sets[0].data) / \ + block_bytes(b->c))) + +#define btree_data_space(b) (PAGE_SIZE << (b)->page_order) + +#define prios_per_bucket(c) \ + ((bucket_bytes(c) - sizeof(struct prio_set)) / \ + sizeof(struct bucket_disk)) +#define prio_buckets(c) \ + DIV_ROUND_UP((size_t) (c)->sb.nbuckets, prios_per_bucket(c)) + +#define JSET_MAGIC 0x245235c1a3625032ULL +#define PSET_MAGIC 0x6750e15f87337f91ULL +#define BSET_MAGIC 0x90135c78b99e07f5ULL + +#define jset_magic(c) ((c)->sb.set_magic ^ JSET_MAGIC) +#define pset_magic(c) ((c)->sb.set_magic ^ PSET_MAGIC) +#define bset_magic(c) ((c)->sb.set_magic ^ BSET_MAGIC) + +/* Bkey fields: all units are in sectors */ + +#define KEY_FIELD(name, field, offset, size) \ + BITMASK(name, struct bkey, field, offset, size) + +#define PTR_FIELD(name, offset, size) \ + static inline uint64_t name(const struct bkey *k, unsigned i) \ + { return (k->ptr[i] >> offset) & ~(((uint64_t) ~0) << size); } \ + \ + static inline void SET_##name(struct bkey *k, unsigned i, uint64_t v)\ + { \ + k->ptr[i] &= ~(~((uint64_t) ~0 << size) << offset); \ + k->ptr[i] |= v << offset; \ + } + +KEY_FIELD(KEY_PTRS, high, 60, 3) +KEY_FIELD(HEADER_SIZE, high, 58, 2) +KEY_FIELD(KEY_CSUM, high, 56, 2) +KEY_FIELD(KEY_PINNED, high, 55, 1) +KEY_FIELD(KEY_DIRTY, high, 36, 1) + +KEY_FIELD(KEY_SIZE, high, 20, 16) +KEY_FIELD(KEY_INODE, high, 0, 20) + +/* Next time I change the on disk format, KEY_OFFSET() won't be 64 bits */ + +static inline uint64_t KEY_OFFSET(const struct bkey *k) +{ + return k->low; +} + +static inline void SET_KEY_OFFSET(struct bkey *k, uint64_t v) +{ + k->low = v; +} + +PTR_FIELD(PTR_DEV, 51, 12) +PTR_FIELD(PTR_OFFSET, 8, 43) +PTR_FIELD(PTR_GEN, 0, 8) + +#define PTR_CHECK_DEV ((1 << 12) - 1) + +#define PTR(gen, offset, dev) \ + ((((uint64_t) dev) << 51) | ((uint64_t) offset) << 8 | gen) + +static inline size_t sector_to_bucket(struct cache_set *c, sector_t s) +{ + return s >> c->bucket_bits; +} + +static inline sector_t bucket_to_sector(struct cache_set *c, size_t b) +{ + return ((sector_t) b) << c->bucket_bits; +} + +static inline sector_t bucket_remainder(struct cache_set *c, sector_t s) +{ + return s & (c->sb.bucket_size - 1); +} + +static inline struct cache *PTR_CACHE(struct cache_set *c, + const struct bkey *k, + unsigned ptr) +{ + return c->cache[PTR_DEV(k, ptr)]; +} + +static inline size_t PTR_BUCKET_NR(struct cache_set *c, + const struct bkey *k, + unsigned ptr) +{ + return sector_to_bucket(c, PTR_OFFSET(k, ptr)); +} + +static inline struct bucket *PTR_BUCKET(struct cache_set *c, + const struct bkey *k, + unsigned ptr) +{ + return PTR_CACHE(c, k, ptr)->buckets + PTR_BUCKET_NR(c, k, ptr); +} + +/* Btree key macros */ + +/* + * The high bit being set is a relic from when we used it to do binary + * searches - it told you where a key started. It's not used anymore, + * and can probably be safely dropped. + */ +#define KEY(dev, sector, len) (struct bkey) \ +{ \ + .high = (1ULL << 63) | ((uint64_t) (len) << 20) | (dev), \ + .low = (sector) \ +} + +static inline void bkey_init(struct bkey *k) +{ + *k = KEY(0, 0, 0); +} + +#define KEY_START(k) (KEY_OFFSET(k) - KEY_SIZE(k)) +#define START_KEY(k) KEY(KEY_INODE(k), KEY_START(k), 0) +#define MAX_KEY KEY(~(~0 << 20), ((uint64_t) ~0) >> 1, 0) +#define ZERO_KEY KEY(0, 0, 0) + +/* + * This is used for various on disk data structures - cache_sb, prio_set, bset, + * jset: The checksum is _always_ the first 8 bytes of these structs + */ +#define csum_set(i) \ + crc64(((void *) (i)) + sizeof(uint64_t), \ + ((void *) end(i)) - (((void *) (i)) + sizeof(uint64_t))) + +/* Error handling macros */ + +#define btree_bug(b, ...) \ +do { \ + if (bch_cache_set_error((b)->c, __VA_ARGS__)) \ + dump_stack(); \ +} while (0) + +#define cache_bug(c, ...) \ +do { \ + if (bch_cache_set_error(c, __VA_ARGS__)) \ + dump_stack(); \ +} while (0) + +#define btree_bug_on(cond, b, ...) \ +do { \ + if (cond) \ + btree_bug(b, __VA_ARGS__); \ +} while (0) + +#define cache_bug_on(cond, c, ...) \ +do { \ + if (cond) \ + cache_bug(c, __VA_ARGS__); \ +} while (0) + +#define cache_set_err_on(cond, c, ...) \ +do { \ + if (cond) \ + bch_cache_set_error(c, __VA_ARGS__); \ +} while (0) + +/* Looping macros */ + +#define for_each_cache(ca, cs, iter) \ + for (iter = 0; ca = cs->cache[iter], iter < (cs)->sb.nr_in_set; iter++) + +#define for_each_bucket(b, ca) \ + for (b = (ca)->buckets + (ca)->sb.first_bucket; \ + b < (ca)->buckets + (ca)->sb.nbuckets; b++) + +static inline void __bkey_put(struct cache_set *c, struct bkey *k) +{ + unsigned i; + + for (i = 0; i < KEY_PTRS(k); i++) + atomic_dec_bug(&PTR_BUCKET(c, k, i)->pin); +} + +/* Blktrace macros */ + +#define blktrace_msg(c, fmt, ...) \ +do { \ + struct request_queue *q = bdev_get_queue(c->bdev); \ + if (q) \ + blk_add_trace_msg(q, fmt, ##__VA_ARGS__); \ +} while (0) + +#define blktrace_msg_all(s, fmt, ...) \ +do { \ + struct cache *_c; \ + unsigned i; \ + for_each_cache(_c, (s), i) \ + blktrace_msg(_c, fmt, ##__VA_ARGS__); \ +} while (0) + +static inline void cached_dev_put(struct cached_dev *dc) +{ + if (atomic_dec_and_test(&dc->count)) + schedule_work(&dc->detach); +} + +static inline bool cached_dev_get(struct cached_dev *dc) +{ + if (!atomic_inc_not_zero(&dc->count)) + return false; + + /* Paired with the mb in cached_dev_attach */ + smp_mb__after_atomic_inc(); + return true; +} + +/* + * bucket_gc_gen() returns the difference between the bucket's current gen and + * the oldest gen of any pointer into that bucket in the btree (last_gc). + * + * bucket_disk_gen() returns the difference between the current gen and the gen + * on disk; they're both used to make sure gens don't wrap around. + */ + +static inline uint8_t bucket_gc_gen(struct bucket *b) +{ + return b->gen - b->last_gc; +} + +static inline uint8_t bucket_disk_gen(struct bucket *b) +{ + return b->gen - b->disk_gen; +} + +#define BUCKET_GC_GEN_MAX 96U +#define BUCKET_DISK_GEN_MAX 64U + +#define kobj_attribute_write(n, fn) \ + static struct kobj_attribute ksysfs_##n = __ATTR(n, S_IWUSR, NULL, fn) + +#define kobj_attribute_rw(n, show, store) \ + static struct kobj_attribute ksysfs_##n = \ + __ATTR(n, S_IWUSR|S_IRUSR, show, store) + +/* Forward declarations */ + +void bch_writeback_queue(struct cached_dev *); +void bch_writeback_add(struct cached_dev *, unsigned); + +void bch_count_io_errors(struct cache *, int, const char *); +void bch_bbio_count_io_errors(struct cache_set *, struct bio *, + int, const char *); +void bch_bbio_endio(struct cache_set *, struct bio *, int, const char *); +void bch_bbio_free(struct bio *, struct cache_set *); +struct bio *bch_bbio_alloc(struct cache_set *); + +struct bio *bch_bio_split(struct bio *, int, gfp_t, struct bio_set *); +void bch_generic_make_request(struct bio *, struct bio_split_pool *); +void __bch_submit_bbio(struct bio *, struct cache_set *); +void bch_submit_bbio(struct bio *, struct cache_set *, struct bkey *, unsigned); + +uint8_t bch_inc_gen(struct cache *, struct bucket *); +void bch_rescale_priorities(struct cache_set *, int); +bool bch_bucket_add_unused(struct cache *, struct bucket *); +void bch_allocator_thread(struct closure *); + +long bch_bucket_alloc(struct cache *, unsigned, struct closure *); +void bch_bucket_free(struct cache_set *, struct bkey *); + +int __bch_bucket_alloc_set(struct cache_set *, unsigned, + struct bkey *, int, struct closure *); +int bch_bucket_alloc_set(struct cache_set *, unsigned, + struct bkey *, int, struct closure *); + +__printf(2, 3) +bool bch_cache_set_error(struct cache_set *, const char *, ...); + +void bch_prio_write(struct cache *); +void bch_write_bdev_super(struct cached_dev *, struct closure *); + +extern struct workqueue_struct *bcache_wq, *bch_gc_wq; +extern const char * const bch_cache_modes[]; +extern struct mutex bch_register_lock; +extern struct list_head bch_cache_sets; + +extern struct kobj_type bch_cached_dev_ktype; +extern struct kobj_type bch_flash_dev_ktype; +extern struct kobj_type bch_cache_set_ktype; +extern struct kobj_type bch_cache_set_internal_ktype; +extern struct kobj_type bch_cache_ktype; + +void bch_cached_dev_release(struct kobject *); +void bch_flash_dev_release(struct kobject *); +void bch_cache_set_release(struct kobject *); +void bch_cache_release(struct kobject *); + +int bch_uuid_write(struct cache_set *); +void bcache_write_super(struct cache_set *); + +int bch_flash_dev_create(struct cache_set *c, uint64_t size); + +int bch_cached_dev_attach(struct cached_dev *, struct cache_set *); +void bch_cached_dev_detach(struct cached_dev *); +void bch_cached_dev_run(struct cached_dev *); +void bcache_device_stop(struct bcache_device *); + +void bch_cache_set_unregister(struct cache_set *); +void bch_cache_set_stop(struct cache_set *); + +struct cache_set *bch_cache_set_alloc(struct cache_sb *); +void bch_btree_cache_free(struct cache_set *); +int bch_btree_cache_alloc(struct cache_set *); +void bch_writeback_init_cached_dev(struct cached_dev *); +void bch_moving_init_cache_set(struct cache_set *); + +void bch_cache_allocator_exit(struct cache *ca); +int bch_cache_allocator_init(struct cache *ca); + +void bch_debug_exit(void); +int bch_debug_init(struct kobject *); +void bch_writeback_exit(void); +int bch_writeback_init(void); +void bch_request_exit(void); +int bch_request_init(void); +void bch_btree_exit(void); +int bch_btree_init(void); + +#endif /* _BCACHE_H */ |