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bcachefs: Fix a KMSAN splat in btree_update_nodes_written()

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We may sometimes read from uninitialized memory; we know, and that's ok.

We check if a btree node has been reused before waiting on any
outstanding IO.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2025-03-20 14:54:49 -04:00
parent 28aa859b6b
commit 1f88c35674
1 changed files with 9 additions and 9 deletions
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18
fs/bcachefs/btree_update_interior.c
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@ -649,6 +649,14 @@ static int btree_update_nodes_written_trans(struct btree_trans *trans,
return 0;
}
/* If the node has been reused, we might be reading uninitialized memory - that's fine: */
static noinline __no_kmsan_checks bool btree_node_seq_matches(struct btree *b, __le64 seq)
{
struct btree_node *b_data = READ_ONCE(b->data);
return (b_data ? b_data->keys.seq : 0) == seq;
}
static void btree_update_nodes_written(struct btree_update *as)
{
struct bch_fs *c = as->c;
@ -677,17 +685,9 @@ static void btree_update_nodes_written(struct btree_update *as)
* on disk:
*/
for (i = 0; i < as->nr_old_nodes; i++) {
__le64 seq;
b = as->old_nodes[i];
bch2_trans_begin(trans);
btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_read);
seq = b->data ? b->data->keys.seq : 0;
six_unlock_read(&b->c.lock);
bch2_trans_unlock_long(trans);
if (seq == as->old_nodes_seq[i])
if (btree_node_seq_matches(b, as->old_nodes_seq[i]))
wait_on_bit_io(&b->flags, BTREE_NODE_write_in_flight_inner,
TASK_UNINTERRUPTIBLE);
}