linux/drivers/md/bcache/alloc.c
Coly Li 4a784266c6 bcache: remove embedded struct cache_sb from struct cache_set
Since bcache code was merged into mainline kerrnel, each cache set only
as one single cache in it. The multiple caches framework is here but the
code is far from completed. Considering the multiple copies of cached
data can also be stored on e.g. md raid1 devices, it is unnecessary to
support multiple caches in one cache set indeed.

The previous preparation patches fix the dependencies of explicitly
making a cache set only have single cache. Now we don't have to maintain
an embedded partial super block in struct cache_set, the in-memory super
block can be directly referenced from struct cache.

This patch removes the embedded struct cache_sb from struct cache_set,
and fixes all locations where the superb lock was referenced from this
removed super block by referencing the in-memory super block of struct
cache.

Signed-off-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-10-02 14:25:30 -06:00

738 lines
19 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Primary bucket allocation code
*
* Copyright 2012 Google, Inc.
*
* Allocation in bcache is done in terms of buckets:
*
* Each bucket has associated an 8 bit gen; this gen corresponds to the gen in
* btree pointers - they must match for the pointer to be considered valid.
*
* Thus (assuming a bucket has no dirty data or metadata in it) we can reuse a
* bucket simply by incrementing its gen.
*
* The gens (along with the priorities; it's really the gens are important but
* the code is named as if it's the priorities) are written in an arbitrary list
* of buckets on disk, with a pointer to them in the journal header.
*
* When we invalidate a bucket, we have to write its new gen to disk and wait
* for that write to complete before we use it - otherwise after a crash we
* could have pointers that appeared to be good but pointed to data that had
* been overwritten.
*
* Since the gens and priorities are all stored contiguously on disk, we can
* batch this up: We fill up the free_inc list with freshly invalidated buckets,
* call prio_write(), and when prio_write() finishes we pull buckets off the
* free_inc list and optionally discard them.
*
* free_inc isn't the only freelist - if it was, we'd often to sleep while
* priorities and gens were being written before we could allocate. c->free is a
* smaller freelist, and buckets on that list are always ready to be used.
*
* If we've got discards enabled, that happens when a bucket moves from the
* free_inc list to the free list.
*
* There is another freelist, because sometimes we have buckets that we know
* have nothing pointing into them - these we can reuse without waiting for
* priorities to be rewritten. These come from freed btree nodes and buckets
* that garbage collection discovered no longer had valid keys pointing into
* them (because they were overwritten). That's the unused list - buckets on the
* unused list move to the free list, optionally being discarded in the process.
*
* It's also important to ensure that gens don't wrap around - with respect to
* either the oldest gen in the btree or the gen on disk. This is quite
* difficult to do in practice, but we explicitly guard against it anyways - if
* a bucket is in danger of wrapping around we simply skip invalidating it that
* time around, and we garbage collect or rewrite the priorities sooner than we
* would have otherwise.
*
* bch_bucket_alloc() allocates a single bucket from a specific cache.
*
* bch_bucket_alloc_set() allocates one bucket from different caches
* out of a cache set.
*
* free_some_buckets() drives all the processes described above. It's called
* from bch_bucket_alloc() and a few other places that need to make sure free
* buckets are ready.
*
* invalidate_buckets_(lru|fifo)() find buckets that are available to be
* invalidated, and then invalidate them and stick them on the free_inc list -
* in either lru or fifo order.
*/
#include "bcache.h"
#include "btree.h"
#include <linux/blkdev.h>
#include <linux/kthread.h>
#include <linux/random.h>
#include <trace/events/bcache.h>
#define MAX_OPEN_BUCKETS 128
/* Bucket heap / gen */
uint8_t bch_inc_gen(struct cache *ca, struct bucket *b)
{
uint8_t ret = ++b->gen;
ca->set->need_gc = max(ca->set->need_gc, bucket_gc_gen(b));
WARN_ON_ONCE(ca->set->need_gc > BUCKET_GC_GEN_MAX);
return ret;
}
void bch_rescale_priorities(struct cache_set *c, int sectors)
{
struct cache *ca;
struct bucket *b;
unsigned long next = c->nbuckets * c->cache->sb.bucket_size / 1024;
int r;
atomic_sub(sectors, &c->rescale);
do {
r = atomic_read(&c->rescale);
if (r >= 0)
return;
} while (atomic_cmpxchg(&c->rescale, r, r + next) != r);
mutex_lock(&c->bucket_lock);
c->min_prio = USHRT_MAX;
ca = c->cache;
for_each_bucket(b, ca)
if (b->prio &&
b->prio != BTREE_PRIO &&
!atomic_read(&b->pin)) {
b->prio--;
c->min_prio = min(c->min_prio, b->prio);
}
mutex_unlock(&c->bucket_lock);
}
/*
* Background allocation thread: scans for buckets to be invalidated,
* invalidates them, rewrites prios/gens (marking them as invalidated on disk),
* then optionally issues discard commands to the newly free buckets, then puts
* them on the various freelists.
*/
static inline bool can_inc_bucket_gen(struct bucket *b)
{
return bucket_gc_gen(b) < BUCKET_GC_GEN_MAX;
}
bool bch_can_invalidate_bucket(struct cache *ca, struct bucket *b)
{
BUG_ON(!ca->set->gc_mark_valid);
return (!GC_MARK(b) ||
GC_MARK(b) == GC_MARK_RECLAIMABLE) &&
!atomic_read(&b->pin) &&
can_inc_bucket_gen(b);
}
void __bch_invalidate_one_bucket(struct cache *ca, struct bucket *b)
{
lockdep_assert_held(&ca->set->bucket_lock);
BUG_ON(GC_MARK(b) && GC_MARK(b) != GC_MARK_RECLAIMABLE);
if (GC_SECTORS_USED(b))
trace_bcache_invalidate(ca, b - ca->buckets);
bch_inc_gen(ca, b);
b->prio = INITIAL_PRIO;
atomic_inc(&b->pin);
}
static void bch_invalidate_one_bucket(struct cache *ca, struct bucket *b)
{
__bch_invalidate_one_bucket(ca, b);
fifo_push(&ca->free_inc, b - ca->buckets);
}
/*
* Determines what order we're going to reuse buckets, smallest bucket_prio()
* first: we also take into account the number of sectors of live data in that
* bucket, and in order for that multiply to make sense we have to scale bucket
*
* Thus, we scale the bucket priorities so that the bucket with the smallest
* prio is worth 1/8th of what INITIAL_PRIO is worth.
*/
#define bucket_prio(b) \
({ \
unsigned int min_prio = (INITIAL_PRIO - ca->set->min_prio) / 8; \
\
(b->prio - ca->set->min_prio + min_prio) * GC_SECTORS_USED(b); \
})
#define bucket_max_cmp(l, r) (bucket_prio(l) < bucket_prio(r))
#define bucket_min_cmp(l, r) (bucket_prio(l) > bucket_prio(r))
static void invalidate_buckets_lru(struct cache *ca)
{
struct bucket *b;
ssize_t i;
ca->heap.used = 0;
for_each_bucket(b, ca) {
if (!bch_can_invalidate_bucket(ca, b))
continue;
if (!heap_full(&ca->heap))
heap_add(&ca->heap, b, bucket_max_cmp);
else if (bucket_max_cmp(b, heap_peek(&ca->heap))) {
ca->heap.data[0] = b;
heap_sift(&ca->heap, 0, bucket_max_cmp);
}
}
for (i = ca->heap.used / 2 - 1; i >= 0; --i)
heap_sift(&ca->heap, i, bucket_min_cmp);
while (!fifo_full(&ca->free_inc)) {
if (!heap_pop(&ca->heap, b, bucket_min_cmp)) {
/*
* We don't want to be calling invalidate_buckets()
* multiple times when it can't do anything
*/
ca->invalidate_needs_gc = 1;
wake_up_gc(ca->set);
return;
}
bch_invalidate_one_bucket(ca, b);
}
}
static void invalidate_buckets_fifo(struct cache *ca)
{
struct bucket *b;
size_t checked = 0;
while (!fifo_full(&ca->free_inc)) {
if (ca->fifo_last_bucket < ca->sb.first_bucket ||
ca->fifo_last_bucket >= ca->sb.nbuckets)
ca->fifo_last_bucket = ca->sb.first_bucket;
b = ca->buckets + ca->fifo_last_bucket++;
if (bch_can_invalidate_bucket(ca, b))
bch_invalidate_one_bucket(ca, b);
if (++checked >= ca->sb.nbuckets) {
ca->invalidate_needs_gc = 1;
wake_up_gc(ca->set);
return;
}
}
}
static void invalidate_buckets_random(struct cache *ca)
{
struct bucket *b;
size_t checked = 0;
while (!fifo_full(&ca->free_inc)) {
size_t n;
get_random_bytes(&n, sizeof(n));
n %= (size_t) (ca->sb.nbuckets - ca->sb.first_bucket);
n += ca->sb.first_bucket;
b = ca->buckets + n;
if (bch_can_invalidate_bucket(ca, b))
bch_invalidate_one_bucket(ca, b);
if (++checked >= ca->sb.nbuckets / 2) {
ca->invalidate_needs_gc = 1;
wake_up_gc(ca->set);
return;
}
}
}
static void invalidate_buckets(struct cache *ca)
{
BUG_ON(ca->invalidate_needs_gc);
switch (CACHE_REPLACEMENT(&ca->sb)) {
case CACHE_REPLACEMENT_LRU:
invalidate_buckets_lru(ca);
break;
case CACHE_REPLACEMENT_FIFO:
invalidate_buckets_fifo(ca);
break;
case CACHE_REPLACEMENT_RANDOM:
invalidate_buckets_random(ca);
break;
}
}
#define allocator_wait(ca, cond) \
do { \
while (1) { \
set_current_state(TASK_INTERRUPTIBLE); \
if (cond) \
break; \
\
mutex_unlock(&(ca)->set->bucket_lock); \
if (kthread_should_stop() || \
test_bit(CACHE_SET_IO_DISABLE, &ca->set->flags)) { \
set_current_state(TASK_RUNNING); \
goto out; \
} \
\
schedule(); \
mutex_lock(&(ca)->set->bucket_lock); \
} \
__set_current_state(TASK_RUNNING); \
} while (0)
static int bch_allocator_push(struct cache *ca, long bucket)
{
unsigned int i;
/* Prios/gens are actually the most important reserve */
if (fifo_push(&ca->free[RESERVE_PRIO], bucket))
return true;
for (i = 0; i < RESERVE_NR; i++)
if (fifo_push(&ca->free[i], bucket))
return true;
return false;
}
static int bch_allocator_thread(void *arg)
{
struct cache *ca = arg;
mutex_lock(&ca->set->bucket_lock);
while (1) {
/*
* First, we pull buckets off of the unused and free_inc lists,
* possibly issue discards to them, then we add the bucket to
* the free list:
*/
while (1) {
long bucket;
if (!fifo_pop(&ca->free_inc, bucket))
break;
if (ca->discard) {
mutex_unlock(&ca->set->bucket_lock);
blkdev_issue_discard(ca->bdev,
bucket_to_sector(ca->set, bucket),
ca->sb.bucket_size, GFP_KERNEL, 0);
mutex_lock(&ca->set->bucket_lock);
}
allocator_wait(ca, bch_allocator_push(ca, bucket));
wake_up(&ca->set->btree_cache_wait);
wake_up(&ca->set->bucket_wait);
}
/*
* We've run out of free buckets, we need to find some buckets
* we can invalidate. First, invalidate them in memory and add
* them to the free_inc list:
*/
retry_invalidate:
allocator_wait(ca, ca->set->gc_mark_valid &&
!ca->invalidate_needs_gc);
invalidate_buckets(ca);
/*
* Now, we write their new gens to disk so we can start writing
* new stuff to them:
*/
allocator_wait(ca, !atomic_read(&ca->set->prio_blocked));
if (CACHE_SYNC(&ca->sb)) {
/*
* This could deadlock if an allocation with a btree
* node locked ever blocked - having the btree node
* locked would block garbage collection, but here we're
* waiting on garbage collection before we invalidate
* and free anything.
*
* But this should be safe since the btree code always
* uses btree_check_reserve() before allocating now, and
* if it fails it blocks without btree nodes locked.
*/
if (!fifo_full(&ca->free_inc))
goto retry_invalidate;
if (bch_prio_write(ca, false) < 0) {
ca->invalidate_needs_gc = 1;
wake_up_gc(ca->set);
}
}
}
out:
wait_for_kthread_stop();
return 0;
}
/* Allocation */
long bch_bucket_alloc(struct cache *ca, unsigned int reserve, bool wait)
{
DEFINE_WAIT(w);
struct bucket *b;
long r;
/* No allocation if CACHE_SET_IO_DISABLE bit is set */
if (unlikely(test_bit(CACHE_SET_IO_DISABLE, &ca->set->flags)))
return -1;
/* fastpath */
if (fifo_pop(&ca->free[RESERVE_NONE], r) ||
fifo_pop(&ca->free[reserve], r))
goto out;
if (!wait) {
trace_bcache_alloc_fail(ca, reserve);
return -1;
}
do {
prepare_to_wait(&ca->set->bucket_wait, &w,
TASK_UNINTERRUPTIBLE);
mutex_unlock(&ca->set->bucket_lock);
schedule();
mutex_lock(&ca->set->bucket_lock);
} while (!fifo_pop(&ca->free[RESERVE_NONE], r) &&
!fifo_pop(&ca->free[reserve], r));
finish_wait(&ca->set->bucket_wait, &w);
out:
if (ca->alloc_thread)
wake_up_process(ca->alloc_thread);
trace_bcache_alloc(ca, reserve);
if (expensive_debug_checks(ca->set)) {
size_t iter;
long i;
unsigned int j;
for (iter = 0; iter < prio_buckets(ca) * 2; iter++)
BUG_ON(ca->prio_buckets[iter] == (uint64_t) r);
for (j = 0; j < RESERVE_NR; j++)
fifo_for_each(i, &ca->free[j], iter)
BUG_ON(i == r);
fifo_for_each(i, &ca->free_inc, iter)
BUG_ON(i == r);
}
b = ca->buckets + r;
BUG_ON(atomic_read(&b->pin) != 1);
SET_GC_SECTORS_USED(b, ca->sb.bucket_size);
if (reserve <= RESERVE_PRIO) {
SET_GC_MARK(b, GC_MARK_METADATA);
SET_GC_MOVE(b, 0);
b->prio = BTREE_PRIO;
} else {
SET_GC_MARK(b, GC_MARK_RECLAIMABLE);
SET_GC_MOVE(b, 0);
b->prio = INITIAL_PRIO;
}
if (ca->set->avail_nbuckets > 0) {
ca->set->avail_nbuckets--;
bch_update_bucket_in_use(ca->set, &ca->set->gc_stats);
}
return r;
}
void __bch_bucket_free(struct cache *ca, struct bucket *b)
{
SET_GC_MARK(b, 0);
SET_GC_SECTORS_USED(b, 0);
if (ca->set->avail_nbuckets < ca->set->nbuckets) {
ca->set->avail_nbuckets++;
bch_update_bucket_in_use(ca->set, &ca->set->gc_stats);
}
}
void bch_bucket_free(struct cache_set *c, struct bkey *k)
{
unsigned int i;
for (i = 0; i < KEY_PTRS(k); i++)
__bch_bucket_free(PTR_CACHE(c, k, i),
PTR_BUCKET(c, k, i));
}
int __bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve,
struct bkey *k, bool wait)
{
struct cache *ca;
long b;
/* No allocation if CACHE_SET_IO_DISABLE bit is set */
if (unlikely(test_bit(CACHE_SET_IO_DISABLE, &c->flags)))
return -1;
lockdep_assert_held(&c->bucket_lock);
bkey_init(k);
ca = c->cache;
b = bch_bucket_alloc(ca, reserve, wait);
if (b == -1)
goto err;
k->ptr[0] = MAKE_PTR(ca->buckets[b].gen,
bucket_to_sector(c, b),
ca->sb.nr_this_dev);
SET_KEY_PTRS(k, 1);
return 0;
err:
bch_bucket_free(c, k);
bkey_put(c, k);
return -1;
}
int bch_bucket_alloc_set(struct cache_set *c, unsigned int reserve,
struct bkey *k, bool wait)
{
int ret;
mutex_lock(&c->bucket_lock);
ret = __bch_bucket_alloc_set(c, reserve, k, wait);
mutex_unlock(&c->bucket_lock);
return ret;
}
/* Sector allocator */
struct open_bucket {
struct list_head list;
unsigned int last_write_point;
unsigned int sectors_free;
BKEY_PADDED(key);
};
/*
* We keep multiple buckets open for writes, and try to segregate different
* write streams for better cache utilization: first we try to segregate flash
* only volume write streams from cached devices, secondly we look for a bucket
* where the last write to it was sequential with the current write, and
* failing that we look for a bucket that was last used by the same task.
*
* The ideas is if you've got multiple tasks pulling data into the cache at the
* same time, you'll get better cache utilization if you try to segregate their
* data and preserve locality.
*
* For example, dirty sectors of flash only volume is not reclaimable, if their
* dirty sectors mixed with dirty sectors of cached device, such buckets will
* be marked as dirty and won't be reclaimed, though the dirty data of cached
* device have been written back to backend device.
*
* And say you've starting Firefox at the same time you're copying a
* bunch of files. Firefox will likely end up being fairly hot and stay in the
* cache awhile, but the data you copied might not be; if you wrote all that
* data to the same buckets it'd get invalidated at the same time.
*
* Both of those tasks will be doing fairly random IO so we can't rely on
* detecting sequential IO to segregate their data, but going off of the task
* should be a sane heuristic.
*/
static struct open_bucket *pick_data_bucket(struct cache_set *c,
const struct bkey *search,
unsigned int write_point,
struct bkey *alloc)
{
struct open_bucket *ret, *ret_task = NULL;
list_for_each_entry_reverse(ret, &c->data_buckets, list)
if (UUID_FLASH_ONLY(&c->uuids[KEY_INODE(&ret->key)]) !=
UUID_FLASH_ONLY(&c->uuids[KEY_INODE(search)]))
continue;
else if (!bkey_cmp(&ret->key, search))
goto found;
else if (ret->last_write_point == write_point)
ret_task = ret;
ret = ret_task ?: list_first_entry(&c->data_buckets,
struct open_bucket, list);
found:
if (!ret->sectors_free && KEY_PTRS(alloc)) {
ret->sectors_free = c->cache->sb.bucket_size;
bkey_copy(&ret->key, alloc);
bkey_init(alloc);
}
if (!ret->sectors_free)
ret = NULL;
return ret;
}
/*
* Allocates some space in the cache to write to, and k to point to the newly
* allocated space, and updates KEY_SIZE(k) and KEY_OFFSET(k) (to point to the
* end of the newly allocated space).
*
* May allocate fewer sectors than @sectors, KEY_SIZE(k) indicates how many
* sectors were actually allocated.
*
* If s->writeback is true, will not fail.
*/
bool bch_alloc_sectors(struct cache_set *c,
struct bkey *k,
unsigned int sectors,
unsigned int write_point,
unsigned int write_prio,
bool wait)
{
struct open_bucket *b;
BKEY_PADDED(key) alloc;
unsigned int i;
/*
* We might have to allocate a new bucket, which we can't do with a
* spinlock held. So if we have to allocate, we drop the lock, allocate
* and then retry. KEY_PTRS() indicates whether alloc points to
* allocated bucket(s).
*/
bkey_init(&alloc.key);
spin_lock(&c->data_bucket_lock);
while (!(b = pick_data_bucket(c, k, write_point, &alloc.key))) {
unsigned int watermark = write_prio
? RESERVE_MOVINGGC
: RESERVE_NONE;
spin_unlock(&c->data_bucket_lock);
if (bch_bucket_alloc_set(c, watermark, &alloc.key, wait))
return false;
spin_lock(&c->data_bucket_lock);
}
/*
* If we had to allocate, we might race and not need to allocate the
* second time we call pick_data_bucket(). If we allocated a bucket but
* didn't use it, drop the refcount bch_bucket_alloc_set() took:
*/
if (KEY_PTRS(&alloc.key))
bkey_put(c, &alloc.key);
for (i = 0; i < KEY_PTRS(&b->key); i++)
EBUG_ON(ptr_stale(c, &b->key, i));
/* Set up the pointer to the space we're allocating: */
for (i = 0; i < KEY_PTRS(&b->key); i++)
k->ptr[i] = b->key.ptr[i];
sectors = min(sectors, b->sectors_free);
SET_KEY_OFFSET(k, KEY_OFFSET(k) + sectors);
SET_KEY_SIZE(k, sectors);
SET_KEY_PTRS(k, KEY_PTRS(&b->key));
/*
* Move b to the end of the lru, and keep track of what this bucket was
* last used for:
*/
list_move_tail(&b->list, &c->data_buckets);
bkey_copy_key(&b->key, k);
b->last_write_point = write_point;
b->sectors_free -= sectors;
for (i = 0; i < KEY_PTRS(&b->key); i++) {
SET_PTR_OFFSET(&b->key, i, PTR_OFFSET(&b->key, i) + sectors);
atomic_long_add(sectors,
&PTR_CACHE(c, &b->key, i)->sectors_written);
}
if (b->sectors_free < c->cache->sb.block_size)
b->sectors_free = 0;
/*
* k takes refcounts on the buckets it points to until it's inserted
* into the btree, but if we're done with this bucket we just transfer
* get_data_bucket()'s refcount.
*/
if (b->sectors_free)
for (i = 0; i < KEY_PTRS(&b->key); i++)
atomic_inc(&PTR_BUCKET(c, &b->key, i)->pin);
spin_unlock(&c->data_bucket_lock);
return true;
}
/* Init */
void bch_open_buckets_free(struct cache_set *c)
{
struct open_bucket *b;
while (!list_empty(&c->data_buckets)) {
b = list_first_entry(&c->data_buckets,
struct open_bucket, list);
list_del(&b->list);
kfree(b);
}
}
int bch_open_buckets_alloc(struct cache_set *c)
{
int i;
spin_lock_init(&c->data_bucket_lock);
for (i = 0; i < MAX_OPEN_BUCKETS; i++) {
struct open_bucket *b = kzalloc(sizeof(*b), GFP_KERNEL);
if (!b)
return -ENOMEM;
list_add(&b->list, &c->data_buckets);
}
return 0;
}
int bch_cache_allocator_start(struct cache *ca)
{
struct task_struct *k = kthread_run(bch_allocator_thread,
ca, "bcache_allocator");
if (IS_ERR(k))
return PTR_ERR(k);
ca->alloc_thread = k;
return 0;
}