Author: jimharris
Date: Mon Nov 23 17:26:20 2015
New Revision: 291213
URL: https://svnweb.freebsd.org/changeset/base/291213
Log:
MFC r290198:
nvme: fix race condition in split bio completion path
Sponsored by: Intel
Modified:
stable/10/sys/dev/nvme/nvme_ns.c
Modified: stable/10/sys/dev/nvme/nvme_ns.c
==============================================================================
--- stable/10/sys/dev/nvme/nvme_ns.c Mon Nov 23 17:09:35 2015
(r291212)
+++ stable/10/sys/dev/nvme/nvme_ns.c Mon Nov 23 17:26:20 2015
(r291213)
@@ -239,7 +239,7 @@ static void
nvme_bio_child_inbed(struct bio *parent, int bio_error)
{
struct nvme_completion parent_cpl;
- int inbed;
+ int children, inbed;
if (bio_error != 0) {
parent->bio_flags |= BIO_ERROR;
@@ -248,10 +248,13 @@ nvme_bio_child_inbed(struct bio *parent,
/*
* atomic_fetchadd will return value before adding 1, so we still
- * must add 1 to get the updated inbed number.
+ * must add 1 to get the updated inbed number. Save bio_children
+ * before incrementing to guard against race conditions when
+ * two children bios complete on different queues.
*/
+ children = atomic_load_acq_int(&parent->bio_children);
inbed = atomic_fetchadd_int(&parent->bio_inbed, 1) + 1;
- if (inbed == parent->bio_children) {
+ if (inbed == children) {
bzero(&parent_cpl, sizeof(parent_cpl));
if (parent->bio_flags & BIO_ERROR)
parent_cpl.status.sc = NVME_SC_DATA_TRANSFER_ERROR;
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