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bcachefs: Fix __bch2_btree_node_lock

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__bch2_btree_node_lock() was implementing the wrong lock ordering for
cached vs. non cached paths - this fixes it to match the btree path sort
order as defined by __btree_path_cmp(), and also simplifies the code
some.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
This commit is contained in:
Kent Overstreet 2022-02-15 22:01:33 -05:00 committed by Kent Overstreet
parent c7ce27328b
commit 7abda8c1d8
1 changed files with 31 additions and 30 deletions
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61
fs/bcachefs/btree_iter.c
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@ -46,6 +46,9 @@ static inline int __btree_path_cmp(const struct btree_path *l,
struct bpos r_pos,
unsigned r_level)
{
/*
* Must match lock ordering as defined by __bch2_btree_node_lock:
*/
return cmp_int(l->btree_id, r_btree_id) ?:
cmp_int((int) l->cached, (int) r_cached) ?:
bpos_cmp(l->pos, r_pos) ?:
@ -288,8 +291,8 @@ bool __bch2_btree_node_lock(struct btree_trans *trans,
six_lock_should_sleep_fn should_sleep_fn, void *p,
unsigned long ip)
{
struct btree_path *linked, *deadlock_path = NULL;
unsigned reason = 9;
struct btree_path *linked;
unsigned reason;
/* Check if it's safe to block: */
trans_for_each_path(trans, linked) {
@ -310,28 +313,28 @@ bool __bch2_btree_node_lock(struct btree_trans *trans,
*/
if (type == SIX_LOCK_intent &&
linked->nodes_locked != linked->nodes_intent_locked) {
deadlock_path = linked;
reason = 1;
goto deadlock;
}
if (linked->btree_id != path->btree_id) {
if (linked->btree_id > path->btree_id) {
deadlock_path = linked;
reason = 3;
}
continue;
if (linked->btree_id < path->btree_id)
continue;
reason = 3;
goto deadlock;
}
/*
* Within the same btree, cached paths come before non
* cached paths:
* Within the same btree, non-cached paths come before cached
* paths:
*/
if (linked->cached != path->cached) {
if (path->cached) {
deadlock_path = linked;
reason = 4;
}
continue;
if (!linked->cached)
continue;
reason = 4;
goto deadlock;
}
/*
@ -340,34 +343,32 @@ bool __bch2_btree_node_lock(struct btree_trans *trans,
* we're about to lock, it must have the ancestors locked too:
*/
if (level > __fls(linked->nodes_locked)) {
deadlock_path = linked;
reason = 5;
goto deadlock;
}
/* Must lock btree nodes in key order: */
if (btree_node_locked(linked, level) &&
bpos_cmp(pos, btree_node_pos((void *) linked->l[level].b,
linked->cached)) <= 0) {
deadlock_path = linked;
reason = 7;
goto deadlock;
}
}
if (unlikely(deadlock_path)) {
trace_trans_restart_would_deadlock(trans->fn, ip,
trans->in_traverse_all, reason,
deadlock_path->btree_id,
deadlock_path->cached,
&deadlock_path->pos,
path->btree_id,
path->cached,
&pos);
btree_trans_restart(trans);
return false;
}
return btree_node_lock_type(trans, path, b, pos, level,
type, should_sleep_fn, p);
deadlock:
trace_trans_restart_would_deadlock(trans->fn, ip,
trans->in_traverse_all, reason,
linked->btree_id,
linked->cached,
&linked->pos,
path->btree_id,
path->cached,
&pos);
btree_trans_restart(trans);
return false;
}
/* Btree iterator locking: */