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bcachefs: key cache: Don't hold btree locks while using GFP_RECLAIM

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This is something we need to do more widely: instead of bothering with
GFP_NOIO/GFP_NOFS, if we need to allocate memory while holding locks:

 - first attempt the allocation with GFP_NOWAIT
 - if that fails, drop btree locks with bch2_trans_unlock(), then
   retry with GFP_KERNEL.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2023-01-07 05:46:52 -05:00
parent 7af365eb36
commit 6c36318cc7
2 changed files with 51 additions and 21 deletions
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2
fs/bcachefs/btree_iter.c
View File

@ -2827,7 +2827,7 @@ u32 bch2_trans_begin(struct btree_trans *trans)
bch2_trans_relock(trans);
}
if (unlikely(time_after(jiffies, trans->srcu_lock_time + HZ)))
if (unlikely(time_after(jiffies, trans->srcu_lock_time + msecs_to_jiffies(10))))
bch2_trans_reset_srcu_lock(trans);
trans->last_restarted_ip = _RET_IP_;

70
fs/bcachefs/btree_key_cache.c
View File

@ -196,6 +196,7 @@ bkey_cached_alloc(struct btree_trans *trans, struct btree_path *path,
struct btree_key_cache *bc = &c->btree_key_cache;
struct bkey_cached *ck = NULL;
bool pcpu_readers = btree_uses_pcpu_readers(path->btree_id);
int ret;
if (!pcpu_readers) {
#ifdef __KERNEL__
@ -263,23 +264,34 @@ bkey_cached_alloc(struct btree_trans *trans, struct btree_path *path,
return ck;
}
/* GFP_NOFS because we're holding btree locks: */
ck = kmem_cache_alloc(bch2_key_cache, GFP_NOFS|__GFP_ZERO);
if (likely(ck)) {
INIT_LIST_HEAD(&ck->list);
__six_lock_init(&ck->c.lock, "b->c.lock", &bch2_btree_node_lock_key);
lockdep_set_novalidate_class(&ck->c.lock);
if (pcpu_readers)
six_lock_pcpu_alloc(&ck->c.lock);
ck = kmem_cache_zalloc(bch2_key_cache, GFP_NOWAIT|__GFP_NOWARN);
if (likely(ck))
goto init;
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;
bch2_trans_unlock(trans);
ck = kmem_cache_zalloc(bch2_key_cache, GFP_KERNEL);
ret = bch2_trans_relock(trans);
if (ret) {
kmem_cache_free(bch2_key_cache, ck);
return ERR_PTR(ret);
}
return NULL;
if (!ck)
return NULL;
init:
INIT_LIST_HEAD(&ck->list);
__six_lock_init(&ck->c.lock, "b->c.lock", &bch2_btree_node_lock_key);
lockdep_set_novalidate_class(&ck->c.lock);
if (pcpu_readers)
six_lock_pcpu_alloc(&ck->c.lock);
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;
}
static struct bkey_cached *
@ -385,7 +397,7 @@ static int btree_key_cache_fill(struct btree_trans *trans,
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_raced);
ret = btree_trans_restart(trans, BCH_ERR_transaction_restart_key_cache_fill);
goto err;
}
@ -404,12 +416,30 @@ static int btree_key_cache_fill(struct btree_trans *trans,
if (new_u64s > ck->u64s) {
new_u64s = roundup_pow_of_two(new_u64s);
new_k = kmalloc(new_u64s * sizeof(u64), GFP_NOFS);
new_k = kmalloc(new_u64s * sizeof(u64), GFP_NOWAIT|__GFP_NOWARN);
if (!new_k) {
bch_err(trans->c, "error allocating memory for key cache key, btree %s u64s %u",
bch2_btree_ids[ck->key.btree_id], new_u64s);
ret = -ENOMEM;
goto err;
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_ids[ck->key.btree_id], new_u64s);
ret = -ENOMEM;
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_trans_relock(trans);
if (ret) {
kfree(new_k);
goto err;
}
}
}