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1/* SPDX-License-Identifier: GPL-2.0 */2#ifndef _BCACHE_JOURNAL_H3#define _BCACHE_JOURNAL_H4 5/*6 * THE JOURNAL:7 *8 * The journal is treated as a circular buffer of buckets - a journal entry9 * never spans two buckets. This means (not implemented yet) we can resize the10 * journal at runtime, and will be needed for bcache on raw flash support.11 *12 * Journal entries contain a list of keys, ordered by the time they were13 * inserted; thus journal replay just has to reinsert the keys.14 *15 * We also keep some things in the journal header that are logically part of the16 * superblock - all the things that are frequently updated. This is for future17 * bcache on raw flash support; the superblock (which will become another18 * journal) can't be moved or wear leveled, so it contains just enough19 * information to find the main journal, and the superblock only has to be20 * rewritten when we want to move/wear level the main journal.21 *22 * Currently, we don't journal BTREE_REPLACE operations - this will hopefully be23 * fixed eventually. This isn't a bug - BTREE_REPLACE is used for insertions24 * from cache misses, which don't have to be journaled, and for writeback and25 * moving gc we work around it by flushing the btree to disk before updating the26 * gc information. But it is a potential issue with incremental garbage27 * collection, and it's fragile.28 *29 * OPEN JOURNAL ENTRIES:30 *31 * Each journal entry contains, in the header, the sequence number of the last32 * journal entry still open - i.e. that has keys that haven't been flushed to33 * disk in the btree.34 *35 * We track this by maintaining a refcount for every open journal entry, in a36 * fifo; each entry in the fifo corresponds to a particular journal37 * entry/sequence number. When the refcount at the tail of the fifo goes to38 * zero, we pop it off - thus, the size of the fifo tells us the number of open39 * journal entries40 *41 * We take a refcount on a journal entry when we add some keys to a journal42 * entry that we're going to insert (held by struct btree_op), and then when we43 * insert those keys into the btree the btree write we're setting up takes a44 * copy of that refcount (held by struct btree_write). That refcount is dropped45 * when the btree write completes.46 *47 * A struct btree_write can only hold a refcount on a single journal entry, but48 * might contain keys for many journal entries - we handle this by making sure49 * it always has a refcount on the _oldest_ journal entry of all the journal50 * entries it has keys for.51 *52 * JOURNAL RECLAIM:53 *54 * As mentioned previously, our fifo of refcounts tells us the number of open55 * journal entries; from that and the current journal sequence number we compute56 * last_seq - the oldest journal entry we still need. We write last_seq in each57 * journal entry, and we also have to keep track of where it exists on disk so58 * we don't overwrite it when we loop around the journal.59 *60 * To do that we track, for each journal bucket, the sequence number of the61 * newest journal entry it contains - if we don't need that journal entry we62 * don't need anything in that bucket anymore. From that we track the last63 * journal bucket we still need; all this is tracked in struct journal_device64 * and updated by journal_reclaim().65 *66 * JOURNAL FILLING UP:67 *68 * There are two ways the journal could fill up; either we could run out of69 * space to write to, or we could have too many open journal entries and run out70 * of room in the fifo of refcounts. Since those refcounts are decremented71 * without any locking we can't safely resize that fifo, so we handle it the72 * same way.73 *74 * If the journal fills up, we start flushing dirty btree nodes until we can75 * allocate space for a journal write again - preferentially flushing btree76 * nodes that are pinning the oldest journal entries first.77 */78 79/*80 * Only used for holding the journal entries we read in btree_journal_read()81 * during cache_registration82 */83struct journal_replay {84 struct list_head list;85 atomic_t *pin;86 struct jset j;87};88 89/*90 * We put two of these in struct journal; we used them for writes to the91 * journal that are being staged or in flight.92 */93struct journal_write {94 struct jset *data;95#define JSET_BITS 396 97 struct cache_set *c;98 struct closure_waitlist wait;99 bool dirty;100 bool need_write;101};102 103/* Embedded in struct cache_set */104struct journal {105 spinlock_t lock;106 spinlock_t flush_write_lock;107 bool btree_flushing;108 bool do_reserve;109 /* used when waiting because the journal was full */110 struct closure_waitlist wait;111 struct closure io;112 int io_in_flight;113 struct delayed_work work;114 115 /* Number of blocks free in the bucket(s) we're currently writing to */116 unsigned int blocks_free;117 uint64_t seq;118 DECLARE_FIFO(atomic_t, pin);119 120 BKEY_PADDED(key);121 122 struct journal_write w[2], *cur;123};124 125/*126 * Embedded in struct cache. First three fields refer to the array of journal127 * buckets, in cache_sb.128 */129struct journal_device {130 /*131 * For each journal bucket, contains the max sequence number of the132 * journal writes it contains - so we know when a bucket can be reused.133 */134 uint64_t seq[SB_JOURNAL_BUCKETS];135 136 /* Journal bucket we're currently writing to */137 unsigned int cur_idx;138 139 /* Last journal bucket that still contains an open journal entry */140 unsigned int last_idx;141 142 /* Next journal bucket to be discarded */143 unsigned int discard_idx;144 145#define DISCARD_READY 0146#define DISCARD_IN_FLIGHT 1147#define DISCARD_DONE 2148 /* 1 - discard in flight, -1 - discard completed */149 atomic_t discard_in_flight;150 151 struct work_struct discard_work;152 struct bio discard_bio;153 struct bio_vec discard_bv;154 155 /* Bio for journal reads/writes to this device */156 struct bio bio;157 struct bio_vec bv[8];158};159 160#define BTREE_FLUSH_NR 8161 162#define journal_pin_cmp(c, l, r) \163 (fifo_idx(&(c)->journal.pin, (l)) > fifo_idx(&(c)->journal.pin, (r)))164 165#define JOURNAL_PIN 20000166 167#define journal_full(j) \168 (!(j)->blocks_free || fifo_free(&(j)->pin) <= 1)169 170struct closure;171struct cache_set;172struct btree_op;173struct keylist;174 175atomic_t *bch_journal(struct cache_set *c,176 struct keylist *keys,177 struct closure *parent);178void bch_journal_next(struct journal *j);179void bch_journal_mark(struct cache_set *c, struct list_head *list);180void bch_journal_meta(struct cache_set *c, struct closure *cl);181int bch_journal_read(struct cache_set *c, struct list_head *list);182int bch_journal_replay(struct cache_set *c, struct list_head *list);183 184void bch_journal_free(struct cache_set *c);185int bch_journal_alloc(struct cache_set *c);186void bch_journal_space_reserve(struct journal *j);187 188#endif /* _BCACHE_JOURNAL_H */189