189 lines
6.5 KiB
C
189 lines
6.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _BCACHE_JOURNAL_H
|
|
#define _BCACHE_JOURNAL_H
|
|
|
|
/*
|
|
* THE JOURNAL:
|
|
*
|
|
* The journal is treated as a circular buffer of buckets - a journal entry
|
|
* never spans two buckets. This means (not implemented yet) we can resize the
|
|
* journal at runtime, and will be needed for bcache on raw flash support.
|
|
*
|
|
* Journal entries contain a list of keys, ordered by the time they were
|
|
* inserted; thus journal replay just has to reinsert the keys.
|
|
*
|
|
* We also keep some things in the journal header that are logically part of the
|
|
* superblock - all the things that are frequently updated. This is for future
|
|
* bcache on raw flash support; the superblock (which will become another
|
|
* journal) can't be moved or wear leveled, so it contains just enough
|
|
* information to find the main journal, and the superblock only has to be
|
|
* rewritten when we want to move/wear level the main journal.
|
|
*
|
|
* Currently, we don't journal BTREE_REPLACE operations - this will hopefully be
|
|
* fixed eventually. This isn't a bug - BTREE_REPLACE is used for insertions
|
|
* from cache misses, which don't have to be journaled, and for writeback and
|
|
* moving gc we work around it by flushing the btree to disk before updating the
|
|
* gc information. But it is a potential issue with incremental garbage
|
|
* collection, and it's fragile.
|
|
*
|
|
* OPEN JOURNAL ENTRIES:
|
|
*
|
|
* Each journal entry contains, in the header, the sequence number of the last
|
|
* journal entry still open - i.e. that has keys that haven't been flushed to
|
|
* disk in the btree.
|
|
*
|
|
* We track this by maintaining a refcount for every open journal entry, in a
|
|
* fifo; each entry in the fifo corresponds to a particular journal
|
|
* entry/sequence number. When the refcount at the tail of the fifo goes to
|
|
* zero, we pop it off - thus, the size of the fifo tells us the number of open
|
|
* journal entries
|
|
*
|
|
* We take a refcount on a journal entry when we add some keys to a journal
|
|
* entry that we're going to insert (held by struct btree_op), and then when we
|
|
* insert those keys into the btree the btree write we're setting up takes a
|
|
* copy of that refcount (held by struct btree_write). That refcount is dropped
|
|
* when the btree write completes.
|
|
*
|
|
* A struct btree_write can only hold a refcount on a single journal entry, but
|
|
* might contain keys for many journal entries - we handle this by making sure
|
|
* it always has a refcount on the _oldest_ journal entry of all the journal
|
|
* entries it has keys for.
|
|
*
|
|
* JOURNAL RECLAIM:
|
|
*
|
|
* As mentioned previously, our fifo of refcounts tells us the number of open
|
|
* journal entries; from that and the current journal sequence number we compute
|
|
* last_seq - the oldest journal entry we still need. We write last_seq in each
|
|
* journal entry, and we also have to keep track of where it exists on disk so
|
|
* we don't overwrite it when we loop around the journal.
|
|
*
|
|
* To do that we track, for each journal bucket, the sequence number of the
|
|
* newest journal entry it contains - if we don't need that journal entry we
|
|
* don't need anything in that bucket anymore. From that we track the last
|
|
* journal bucket we still need; all this is tracked in struct journal_device
|
|
* and updated by journal_reclaim().
|
|
*
|
|
* JOURNAL FILLING UP:
|
|
*
|
|
* There are two ways the journal could fill up; either we could run out of
|
|
* space to write to, or we could have too many open journal entries and run out
|
|
* of room in the fifo of refcounts. Since those refcounts are decremented
|
|
* without any locking we can't safely resize that fifo, so we handle it the
|
|
* same way.
|
|
*
|
|
* If the journal fills up, we start flushing dirty btree nodes until we can
|
|
* allocate space for a journal write again - preferentially flushing btree
|
|
* nodes that are pinning the oldest journal entries first.
|
|
*/
|
|
|
|
/*
|
|
* Only used for holding the journal entries we read in btree_journal_read()
|
|
* during cache_registration
|
|
*/
|
|
struct journal_replay {
|
|
struct list_head list;
|
|
atomic_t *pin;
|
|
struct jset j;
|
|
};
|
|
|
|
/*
|
|
* We put two of these in struct journal; we used them for writes to the
|
|
* journal that are being staged or in flight.
|
|
*/
|
|
struct journal_write {
|
|
struct jset *data;
|
|
#define JSET_BITS 3
|
|
|
|
struct cache_set *c;
|
|
struct closure_waitlist wait;
|
|
bool dirty;
|
|
bool need_write;
|
|
};
|
|
|
|
/* Embedded in struct cache_set */
|
|
struct journal {
|
|
spinlock_t lock;
|
|
spinlock_t flush_write_lock;
|
|
bool btree_flushing;
|
|
bool do_reserve;
|
|
/* used when waiting because the journal was full */
|
|
struct closure_waitlist wait;
|
|
struct closure io;
|
|
int io_in_flight;
|
|
struct delayed_work work;
|
|
|
|
/* Number of blocks free in the bucket(s) we're currently writing to */
|
|
unsigned int blocks_free;
|
|
uint64_t seq;
|
|
DECLARE_FIFO(atomic_t, pin);
|
|
|
|
BKEY_PADDED(key);
|
|
|
|
struct journal_write w[2], *cur;
|
|
};
|
|
|
|
/*
|
|
* Embedded in struct cache. First three fields refer to the array of journal
|
|
* buckets, in cache_sb.
|
|
*/
|
|
struct journal_device {
|
|
/*
|
|
* For each journal bucket, contains the max sequence number of the
|
|
* journal writes it contains - so we know when a bucket can be reused.
|
|
*/
|
|
uint64_t seq[SB_JOURNAL_BUCKETS];
|
|
|
|
/* Journal bucket we're currently writing to */
|
|
unsigned int cur_idx;
|
|
|
|
/* Last journal bucket that still contains an open journal entry */
|
|
unsigned int last_idx;
|
|
|
|
/* Next journal bucket to be discarded */
|
|
unsigned int discard_idx;
|
|
|
|
#define DISCARD_READY 0
|
|
#define DISCARD_IN_FLIGHT 1
|
|
#define DISCARD_DONE 2
|
|
/* 1 - discard in flight, -1 - discard completed */
|
|
atomic_t discard_in_flight;
|
|
|
|
struct work_struct discard_work;
|
|
struct bio discard_bio;
|
|
struct bio_vec discard_bv;
|
|
|
|
/* Bio for journal reads/writes to this device */
|
|
struct bio bio;
|
|
struct bio_vec bv[8];
|
|
};
|
|
|
|
#define BTREE_FLUSH_NR 8
|
|
|
|
#define journal_pin_cmp(c, l, r) \
|
|
(fifo_idx(&(c)->journal.pin, (l)) > fifo_idx(&(c)->journal.pin, (r)))
|
|
|
|
#define JOURNAL_PIN 20000
|
|
|
|
#define journal_full(j) \
|
|
(!(j)->blocks_free || fifo_free(&(j)->pin) <= 1)
|
|
|
|
struct closure;
|
|
struct cache_set;
|
|
struct btree_op;
|
|
struct keylist;
|
|
|
|
atomic_t *bch_journal(struct cache_set *c,
|
|
struct keylist *keys,
|
|
struct closure *parent);
|
|
void bch_journal_next(struct journal *j);
|
|
void bch_journal_mark(struct cache_set *c, struct list_head *list);
|
|
void bch_journal_meta(struct cache_set *c, struct closure *cl);
|
|
int bch_journal_read(struct cache_set *c, struct list_head *list);
|
|
int bch_journal_replay(struct cache_set *c, struct list_head *list);
|
|
|
|
void bch_journal_free(struct cache_set *c);
|
|
int bch_journal_alloc(struct cache_set *c);
|
|
void bch_journal_space_reserve(struct journal *j);
|
|
|
|
#endif /* _BCACHE_JOURNAL_H */
|