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bcachefs: Simplify btree key cache fill path

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Don't allocate the new bkey_cached until after we've done the btree
lookup; this means we can kill bkey_cached.valid.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-06-08 17:49:11 -04:00
parent 39d5d8290c
commit d2cb6b219d
3 changed files with 125 additions and 208 deletions
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9
fs/bcachefs/btree_iter.c
View File

@ -1800,13 +1800,12 @@ struct bkey_s_c bch2_btree_path_peek_slot(struct btree_path *path, struct bkey *
goto hole;
} else {
struct bkey_cached *ck = (void *) path->l[0].b;
EBUG_ON(ck &&
(path->btree_id != ck->key.btree_id ||
!bkey_eq(path->pos, ck->key.pos)));
if (!ck || !ck->valid)
if (!ck)
return bkey_s_c_null;
EBUG_ON(path->btree_id != ck->key.btree_id ||
!bkey_eq(path->pos, ck->key.pos));
*u = ck->k->k;
k = bkey_i_to_s_c(ck->k);
}

323
fs/bcachefs/btree_key_cache.c
View File

@ -205,9 +205,22 @@ static void bkey_cached_free_fast(struct btree_key_cache *bc,
six_unlock_intent(&ck->c.lock);
}
static struct bkey_cached *__bkey_cached_alloc(unsigned key_u64s, gfp_t gfp)
{
struct bkey_cached *ck = kmem_cache_zalloc(bch2_key_cache, gfp);
if (unlikely(!ck))
return NULL;
ck->k = kmalloc(key_u64s * sizeof(u64), gfp);
if (unlikely(!ck->k)) {
kmem_cache_free(bch2_key_cache, ck);
return NULL;
}
ck->u64s = key_u64s;
return ck;
}
static struct bkey_cached *
bkey_cached_alloc(struct btree_trans *trans, struct btree_path *path,
bool *was_new)
bkey_cached_alloc(struct btree_trans *trans, struct btree_path *path, unsigned key_u64s)
{
struct bch_fs *c = trans->c;
struct btree_key_cache *bc = &c->btree_key_cache;
@ -281,8 +294,10 @@ bkey_cached_alloc(struct btree_trans *trans, struct btree_path *path,
}
ck = allocate_dropping_locks(trans, ret,
kmem_cache_zalloc(bch2_key_cache, _gfp));
__bkey_cached_alloc(key_u64s, _gfp));
if (ret) {
if (ck)
kfree(ck->k);
kmem_cache_free(bch2_key_cache, ck);
return ERR_PTR(ret);
}
@ -296,7 +311,6 @@ bkey_cached_alloc(struct btree_trans *trans, struct btree_path *path,
ck->c.cached = true;
BUG_ON(!six_trylock_intent(&ck->c.lock));
BUG_ON(!six_trylock_write(&ck->c.lock));
*was_new = true;
return ck;
}
@ -326,71 +340,102 @@ out:
return ck;
}
static struct bkey_cached *
btree_key_cache_create(struct btree_trans *trans, struct btree_path *path)
static int btree_key_cache_create(struct btree_trans *trans, struct btree_path *path,
struct bkey_s_c k)
{
struct bch_fs *c = trans->c;
struct btree_key_cache *bc = &c->btree_key_cache;
struct bkey_cached *ck;
bool was_new = false;
ck = bkey_cached_alloc(trans, path, &was_new);
if (IS_ERR(ck))
return ck;
/*
* bch2_varint_decode can read past the end of the buffer by at
* most 7 bytes (it won't be used):
*/
unsigned key_u64s = k.k->u64s + 1;
/*
* Allocate some extra space so that the transaction commit path is less
* likely to have to reallocate, since that requires a transaction
* restart:
*/
key_u64s = min(256U, (key_u64s * 3) / 2);
key_u64s = roundup_pow_of_two(key_u64s);
struct bkey_cached *ck = bkey_cached_alloc(trans, path, key_u64s);
int ret = PTR_ERR_OR_ZERO(ck);
if (ret)
return ret;
if (unlikely(!ck)) {
ck = bkey_cached_reuse(bc);
if (unlikely(!ck)) {
bch_err(c, "error allocating memory for key cache item, btree %s",
bch2_btree_id_str(path->btree_id));
return ERR_PTR(-BCH_ERR_ENOMEM_btree_key_cache_create);
return -BCH_ERR_ENOMEM_btree_key_cache_create;
}
mark_btree_node_locked(trans, path, 0, BTREE_NODE_INTENT_LOCKED);
}
ck->c.level = 0;
ck->c.btree_id = path->btree_id;
ck->key.btree_id = path->btree_id;
ck->key.pos = path->pos;
ck->valid = false;
ck->flags = 1U << BKEY_CACHED_ACCESSED;
if (unlikely(rhashtable_lookup_insert_fast(&bc->table,
&ck->hash,
bch2_btree_key_cache_params))) {
/* We raced with another fill: */
if (unlikely(key_u64s > ck->u64s)) {
mark_btree_node_locked_noreset(path, 0, BTREE_NODE_UNLOCKED);
if (likely(was_new)) {
six_unlock_write(&ck->c.lock);
six_unlock_intent(&ck->c.lock);
kfree(ck);
} else {
bkey_cached_free_fast(bc, ck);
struct bkey_i *new_k = allocate_dropping_locks(trans, ret,
kmalloc(key_u64s * sizeof(u64), _gfp));
if (unlikely(!new_k)) {
bch_err(trans->c, "error allocating memory for key cache key, btree %s u64s %u",
bch2_btree_id_str(ck->key.btree_id), key_u64s);
ret = -BCH_ERR_ENOMEM_btree_key_cache_fill;
} else if (ret) {
kfree(new_k);
goto err;
}
mark_btree_node_locked(trans, path, 0, BTREE_NODE_UNLOCKED);
return NULL;
kfree(ck->k);
ck->k = new_k;
ck->u64s = key_u64s;
}
atomic_long_inc(&bc->nr_keys);
bkey_reassemble(ck->k, k);
ret = rhashtable_lookup_insert_fast(&bc->table, &ck->hash, bch2_btree_key_cache_params);
if (unlikely(ret)) /* raced with another fill? */
goto err;
atomic_long_inc(&bc->nr_keys);
six_unlock_write(&ck->c.lock);
return ck;
enum six_lock_type lock_want = __btree_lock_want(path, 0);
if (lock_want == SIX_LOCK_read)
six_lock_downgrade(&ck->c.lock);
btree_path_cached_set(trans, path, ck, (enum btree_node_locked_type) lock_want);
path->uptodate = BTREE_ITER_UPTODATE;
return 0;
err:
bkey_cached_free_fast(bc, ck);
mark_btree_node_locked_noreset(path, 0, BTREE_NODE_UNLOCKED);
return ret;
}
static int btree_key_cache_fill(struct btree_trans *trans,
struct btree_path *ck_path,
struct bkey_cached *ck)
static noinline int btree_key_cache_fill(struct btree_trans *trans,
struct btree_path *ck_path,
unsigned flags)
{
if (flags & BTREE_ITER_cached_nofill) {
ck_path->uptodate = BTREE_ITER_UPTODATE;
return 0;
}
struct bch_fs *c = trans->c;
struct btree_iter iter;
struct bkey_s_c k;
unsigned new_u64s = 0;
struct bkey_i *new_k = NULL;
int ret;
bch2_trans_iter_init(trans, &iter, ck->key.btree_id, ck->key.pos,
bch2_trans_iter_init(trans, &iter, ck_path->btree_id, ck_path->pos,
BTREE_ITER_key_cache_fill|
BTREE_ITER_cached_nofill);
iter.flags &= ~BTREE_ITER_with_journal;
@ -399,70 +444,15 @@ static int btree_key_cache_fill(struct btree_trans *trans,
if (ret)
goto err;
if (!bch2_btree_node_relock(trans, ck_path, 0)) {
trace_and_count(trans->c, trans_restart_relock_key_cache_fill, trans, _THIS_IP_, ck_path);
ret = btree_trans_restart(trans, BCH_ERR_transaction_restart_key_cache_fill);
/* Recheck after btree lookup, before allocating: */
ret = bch2_btree_key_cache_find(c, ck_path->btree_id, ck_path->pos) ? -EEXIST : 0;
if (unlikely(ret))
goto out;
ret = btree_key_cache_create(trans, ck_path, k);
if (ret)
goto err;
}
/*
* bch2_varint_decode can read past the end of the buffer by at
* most 7 bytes (it won't be used):
*/
new_u64s = k.k->u64s + 1;
/*
* Allocate some extra space so that the transaction commit path is less
* likely to have to reallocate, since that requires a transaction
* restart:
*/
new_u64s = min(256U, (new_u64s * 3) / 2);
if (new_u64s > ck->u64s) {
new_u64s = roundup_pow_of_two(new_u64s);
new_k = kmalloc(new_u64s * sizeof(u64), GFP_NOWAIT|__GFP_NOWARN);
if (!new_k) {
bch2_trans_unlock(trans);
new_k = kmalloc(new_u64s * sizeof(u64), GFP_KERNEL);
if (!new_k) {
bch_err(trans->c, "error allocating memory for key cache key, btree %s u64s %u",
bch2_btree_id_str(ck->key.btree_id), new_u64s);
ret = -BCH_ERR_ENOMEM_btree_key_cache_fill;
goto err;
}
ret = bch2_trans_relock(trans);
if (ret) {
kfree(new_k);
goto err;
}
if (!bch2_btree_node_relock(trans, ck_path, 0)) {
kfree(new_k);
trace_and_count(trans->c, trans_restart_relock_key_cache_fill, trans, _THIS_IP_, ck_path);
ret = btree_trans_restart(trans, BCH_ERR_transaction_restart_key_cache_fill);
goto err;
}
}
}
ret = bch2_btree_node_lock_write(trans, ck_path, &ck_path->l[0].b->c);
if (ret) {
kfree(new_k);
goto err;
}
if (new_k) {
kfree(ck->k);
ck->u64s = new_u64s;
ck->k = new_k;
}
bkey_reassemble(ck->k, k);
ck->valid = true;
bch2_btree_node_unlock_write(trans, ck_path, ck_path->l[0].b);
out:
/* We're not likely to need this iterator again: */
bch2_set_btree_iter_dontneed(&iter);
err:
@ -470,107 +460,19 @@ err:
return ret;
}
static noinline int
bch2_btree_path_traverse_cached_slowpath(struct btree_trans *trans, struct btree_path *path,
unsigned flags)
static inline int btree_path_traverse_cached_fast(struct btree_trans *trans,
struct btree_path *path)
{
struct bch_fs *c = trans->c;
struct bkey_cached *ck;
int ret = 0;
BUG_ON(path->level);
path->l[1].b = NULL;
if (bch2_btree_node_relock_notrace(trans, path, 0)) {
ck = (void *) path->l[0].b;
goto fill;
}
retry:
ck = bch2_btree_key_cache_find(c, path->btree_id, path->pos);
if (!ck) {
ck = btree_key_cache_create(trans, path);
ret = PTR_ERR_OR_ZERO(ck);
if (ret)
goto err;
if (!ck)
goto retry;
btree_path_cached_set(trans, path, ck, BTREE_NODE_INTENT_LOCKED);
path->locks_want = 1;
} else {
enum six_lock_type lock_want = __btree_lock_want(path, 0);
ret = btree_node_lock(trans, path, (void *) ck, 0,
lock_want, _THIS_IP_);
if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
goto err;
BUG_ON(ret);
if (ck->key.btree_id != path->btree_id ||
!bpos_eq(ck->key.pos, path->pos)) {
six_unlock_type(&ck->c.lock, lock_want);
goto retry;
}
btree_path_cached_set(trans, path, ck, (enum btree_node_locked_type) lock_want);
}
fill:
path->uptodate = BTREE_ITER_UPTODATE;
if (!ck->valid && !(flags & BTREE_ITER_cached_nofill)) {
ret = bch2_btree_path_upgrade(trans, path, 1) ?:
btree_key_cache_fill(trans, path, ck) ?:
bch2_btree_path_relock(trans, path, _THIS_IP_);
if (ret)
goto err;
path->uptodate = BTREE_ITER_UPTODATE;
}
if (!test_bit(BKEY_CACHED_ACCESSED, &ck->flags))
set_bit(BKEY_CACHED_ACCESSED, &ck->flags);
BUG_ON(btree_node_locked_type(path, 0) != btree_lock_want(path, 0));
BUG_ON(path->uptodate);
return ret;
err:
path->uptodate = BTREE_ITER_NEED_TRAVERSE;
if (!bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
btree_node_unlock(trans, path, 0);
path->l[0].b = ERR_PTR(ret);
}
return ret;
}
int bch2_btree_path_traverse_cached(struct btree_trans *trans, struct btree_path *path,
unsigned flags)
{
struct bch_fs *c = trans->c;
struct bkey_cached *ck;
int ret = 0;
EBUG_ON(path->level);
path->l[1].b = NULL;
if (bch2_btree_node_relock_notrace(trans, path, 0)) {
ck = (void *) path->l[0].b;
goto fill;
}
retry:
ck = bch2_btree_key_cache_find(c, path->btree_id, path->pos);
if (!ck)
return bch2_btree_path_traverse_cached_slowpath(trans, path, flags);
return -ENOENT;
enum six_lock_type lock_want = __btree_lock_want(path, 0);
ret = btree_node_lock(trans, path, (void *) ck, 0,
lock_want, _THIS_IP_);
EBUG_ON(ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart));
int ret = btree_node_lock(trans, path, (void *) ck, 0, lock_want, _THIS_IP_);
if (ret)
return ret;
@ -580,18 +482,40 @@ retry:
goto retry;
}
btree_path_cached_set(trans, path, ck, (enum btree_node_locked_type) lock_want);
fill:
if (!ck->valid)
return bch2_btree_path_traverse_cached_slowpath(trans, path, flags);
if (!test_bit(BKEY_CACHED_ACCESSED, &ck->flags))
set_bit(BKEY_CACHED_ACCESSED, &ck->flags);
btree_path_cached_set(trans, path, ck, (enum btree_node_locked_type) lock_want);
path->uptodate = BTREE_ITER_UPTODATE;
EBUG_ON(!ck->valid);
EBUG_ON(btree_node_locked_type(path, 0) != btree_lock_want(path, 0));
return 0;
}
int bch2_btree_path_traverse_cached(struct btree_trans *trans, struct btree_path *path,
unsigned flags)
{
EBUG_ON(path->level);
path->l[1].b = NULL;
if (bch2_btree_node_relock_notrace(trans, path, 0)) {
path->uptodate = BTREE_ITER_UPTODATE;
return 0;
}
int ret;
do {
ret = btree_path_traverse_cached_fast(trans, path);
if (unlikely(ret == -ENOENT))
ret = btree_key_cache_fill(trans, path, flags);
} while (ret == -EEXIST);
if (unlikely(ret)) {
path->uptodate = BTREE_ITER_NEED_TRAVERSE;
if (!bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
btree_node_unlock(trans, path, 0);
path->l[0].b = ERR_PTR(ret);
}
}
return ret;
}
@ -630,8 +554,6 @@ static int btree_key_cache_flush_pos(struct btree_trans *trans,
goto out;
}
BUG_ON(!ck->valid);
if (journal_seq && ck->journal.seq != journal_seq)
goto out;
@ -753,7 +675,6 @@ bool bch2_btree_insert_key_cached(struct btree_trans *trans,
BUG_ON(insert->k.u64s > ck->u64s);
bkey_copy(ck->k, insert);
ck->valid = true;
if (!test_bit(BKEY_CACHED_DIRTY, &ck->flags)) {
EBUG_ON(test_bit(BCH_FS_clean_shutdown, &c->flags));
@ -795,8 +716,6 @@ void bch2_btree_key_cache_drop(struct btree_trans *trans,
struct btree_key_cache *bc = &c->btree_key_cache;
struct bkey_cached *ck = (void *) path->l[0].b;
BUG_ON(!ck->valid);
/*
* We just did an update to the btree, bypassing the key cache: the key
* cache key is now stale and must be dropped, even if dirty:

1
fs/bcachefs/btree_types.h
View File

@ -388,7 +388,6 @@ struct bkey_cached {
unsigned long flags;
unsigned long btree_trans_barrier_seq;
u16 u64s;
bool valid;
struct bkey_cached_key key;
struct rhash_head hash;