Commit 09b0283e authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: Make sure to drop/retake btree locks before reclaim 



We really don't want to be invoking memory reclaim with btree locks
held: even aside from (solvable, but tricky) recursion issues, it can
cause painful to diagnose performance edge cases.

This fixes a recently reported issue in btree_key_can_insert_cached().

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
Reported-by: default avatarMateusz Guzik <mjguzik@gmail.com>
Fixes: https://lore.kernel.org/linux-bcachefs/CAGudoHEsb_hGRMeWeXh+UF6po0qQuuq_NKSEo+s1sEb6bDLjpA@mail.gmail.com/T/
parent 3b8c4507

fs/bcachefs/btree_trans_commit.c

+42 −6
Original line number Diff line number Diff line
@@ -368,6 +368,45 @@ static inline int btree_key_can_insert(struct btree_trans *trans, 
	return 0;

}



noinline static int

btree_key_can_insert_cached_slowpath(struct btree_trans *trans, unsigned flags,

				     struct btree_path *path, unsigned new_u64s)

{

	struct bch_fs *c = trans->c;

	struct btree_insert_entry *i;

	struct bkey_cached *ck = (void *) path->l[0].b;

	struct bkey_i *new_k;

	int ret;



	bch2_trans_unlock_write(trans);

	bch2_trans_unlock(trans);



	new_k = kmalloc(new_u64s * sizeof(u64), GFP_KERNEL);

	if (!new_k) {

		bch_err(c, "error allocating memory for key cache key, btree %s u64s %u",

			bch2_btree_id_str(path->btree_id), new_u64s);

		return -BCH_ERR_ENOMEM_btree_key_cache_insert;

	}



	ret =   bch2_trans_relock(trans) ?:

		bch2_trans_lock_write(trans);

	if (unlikely(ret)) {

		kfree(new_k);

		return ret;

	}



	memcpy(new_k, ck->k, ck->u64s * sizeof(u64));



	trans_for_each_update(trans, i)

		if (i->old_v == &ck->k->v)

			i->old_v = &new_k->v;



	kfree(ck->k);

	ck->u64s	= new_u64s;

	ck->k		= new_k;

	return 0;

}



static int btree_key_can_insert_cached(struct btree_trans *trans, unsigned flags,

				       struct btree_path *path, unsigned u64s)

{
@@ -394,12 +433,9 @@ static int btree_key_can_insert_cached(struct btree_trans *trans, unsigned flags 
		return 0;



	new_u64s	= roundup_pow_of_two(u64s);

	new_k		= krealloc(ck->k, new_u64s * sizeof(u64), GFP_NOFS);

	if (!new_k) {

		bch_err(c, "error allocating memory for key cache key, btree %s u64s %u",

			bch2_btree_id_str(path->btree_id), new_u64s);

		return -BCH_ERR_ENOMEM_btree_key_cache_insert;

	}

	new_k		= krealloc(ck->k, new_u64s * sizeof(u64), GFP_NOWAIT);

	if (unlikely(!new_k))

		return btree_key_can_insert_cached_slowpath(trans, flags, path, new_u64s);



	trans_for_each_update(trans, i)

		if (i->old_v == &ck->k->v)