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bcachefs: Fix another deadlock in the btree interior update path

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Can't take read locks on btree nodes while holding
btree_interior_update_lock. Also, fix a bug where we were leaking
journal prereservations.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2020-04-07 17:27:12 -04:00 committed by Kent Overstreet
parent 1eba942d1c
commit 58fb3e519a
1 changed files with 42 additions and 29 deletions
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71
fs/bcachefs/btree_update_interior.c
View file

@ -609,33 +609,11 @@ static void bch2_btree_update_free(struct btree_update *as)
mutex_unlock(&c->btree_interior_update_lock);
}
static void btree_update_nodes_reachable(struct btree_update *as, u64 seq)
{
struct bch_fs *c = as->c;
while (as->nr_new_nodes) {
struct btree *b = as->new_nodes[--as->nr_new_nodes];
BUG_ON(b->will_make_reachable != (unsigned long) as);
b->will_make_reachable = 0;
/*
* b->will_make_reachable prevented it from being written, so
* write it now if it needs to be written:
*/
btree_node_lock_type(c, b, SIX_LOCK_read);
bch2_btree_node_write_cond(c, b, btree_node_need_write(b));
six_unlock_read(&b->c.lock);
}
while (as->nr_pending)
bch2_btree_node_free_ondisk(c, &as->pending[--as->nr_pending],
seq);
}
static void btree_update_nodes_written(struct closure *cl)
{
struct btree_update *as = container_of(cl, struct btree_update, cl);
struct btree *new_nodes[BTREE_MAX_DEPTH * 2 + GC_MERGE_NODES];
unsigned nr_new_nodes;
struct journal_res res = { 0 };
struct bch_fs *c = as->c;
struct btree *b;
@ -650,6 +628,7 @@ static void btree_update_nodes_written(struct closure *cl)
mutex_lock(&c->btree_interior_update_lock);
as->nodes_written = true;
again:
nr_new_nodes = 0;
as = list_first_entry_or_null(&c->btree_interior_updates_unwritten,
struct btree_update, unwritten_list);
if (!as || !as->nodes_written) {
@ -738,8 +717,23 @@ static void btree_update_nodes_written(struct closure *cl)
six_unlock_intent(&b->c.lock);
}
if (!ret)
btree_update_nodes_reachable(as, res.seq);
if (!ret) {
nr_new_nodes = as->nr_new_nodes;
memcpy(new_nodes,
as->new_nodes,
as->nr_new_nodes * sizeof(struct btree *));
while (as->nr_new_nodes) {
struct btree *b = as->new_nodes[--as->nr_new_nodes];
BUG_ON(b->will_make_reachable != (unsigned long) as);
b->will_make_reachable = 0;
}
while (as->nr_pending)
bch2_btree_node_free_ondisk(c,
&as->pending[--as->nr_pending], res.seq);
}
__bch2_btree_update_free(as);
/*
@ -747,6 +741,20 @@ static void btree_update_nodes_written(struct closure *cl)
* nodes to be writeable:
*/
closure_wake_up(&c->btree_interior_update_wait);
/*
* Can't take btree node locks while holding btree_interior_update_lock:
* */
mutex_unlock(&c->btree_interior_update_lock);
while (nr_new_nodes) {
struct btree *b = new_nodes[--nr_new_nodes];
btree_node_lock_type(c, b, SIX_LOCK_read);
bch2_btree_node_write_cond(c, b, btree_node_need_write(b));
six_unlock_read(&b->c.lock);
}
mutex_lock(&c->btree_interior_update_lock);
goto again;
}
@ -963,11 +971,13 @@ bch2_btree_update_start(struct btree_trans *trans, enum btree_id id,
BTREE_UPDATE_JOURNAL_RES,
JOURNAL_RES_GET_NONBLOCK);
if (ret == -EAGAIN) {
if (flags & BTREE_INSERT_NOUNLOCK)
return ERR_PTR(-EINTR);
bch2_trans_unlock(trans);
ret = bch2_journal_preres_get(&c->journal, &journal_preres,
BTREE_UPDATE_JOURNAL_RES,
JOURNAL_RES_GET_NONBLOCK);
BTREE_UPDATE_JOURNAL_RES, 0);
if (ret)
return ERR_PTR(ret);
@ -978,8 +988,10 @@ bch2_btree_update_start(struct btree_trans *trans, enum btree_id id,
}
reserve = bch2_btree_reserve_get(c, nr_nodes, flags, cl);
if (IS_ERR(reserve))
if (IS_ERR(reserve)) {
bch2_journal_preres_put(&c->journal, &journal_preres);
return ERR_CAST(reserve);
}
as = mempool_alloc(&c->btree_interior_update_pool, GFP_NOIO);
memset(as, 0, sizeof(*as));
@ -1677,6 +1689,7 @@ void __bch2_foreground_maybe_merge(struct bch_fs *c,
as = bch2_btree_update_start(trans, iter->btree_id,
btree_update_reserve_required(c, parent) + 1,
flags|
BTREE_INSERT_NOFAIL|
BTREE_INSERT_USE_RESERVE,
!(flags & BTREE_INSERT_NOUNLOCK) ? &cl : NULL);