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

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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: Kent Overstreet <kent.overstreet@linux.dev>
Reported-by: Mateusz Guzik <mjguzik@gmail.com>
Fixes: https://lore.kernel.org/linux-bcachefs/CAGudoHEsb_hGRMeWeXh+UF6po0qQuuq_NKSEo+s1sEb6bDLjpA@mail.gmail.com/T/
This commit is contained in:
Kent Overstreet 2023-11-05 15:28:44 -05:00
parent 3b8c450777
commit 09b0283ee2
1 changed files with 42 additions and 6 deletions
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48
fs/bcachefs/btree_trans_commit.c
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@ -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)