[src/trunk]: src/sys/dev/dm dm: Fix race on pdev create

[tkusumi <tkusumi%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/e57779dc1c84
branches:  trunk
changeset: 461611:e57779dc1c84
user:      tkusumi <tkusumi%NetBSD.org@localhost>
date:      Sun Dec 01 16:33:33 2019 +0000

description:
dm: Fix race on pdev create

List lookup and insert need to be atomic.
https://github.com/DragonFlyBSD/DragonFlyBSD/commit/ac816675c8321309b49d6a335f95c5388036803f

take-from: DragonFlyBSD

diffstat:

 sys/dev/dm/dm_pdev.c |  12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diffs (53 lines):

diff -r d3c518d1427a -r e57779dc1c84 sys/dev/dm/dm_pdev.c
--- a/sys/dev/dm/dm_pdev.c      Sun Dec 01 16:32:01 2019 +0000
+++ b/sys/dev/dm/dm_pdev.c      Sun Dec 01 16:33:33 2019 +0000
@@ -1,4 +1,4 @@
-/*        $NetBSD: dm_pdev.c,v 1.10 2018/01/05 14:22:26 christos Exp $      */
+/*        $NetBSD: dm_pdev.c,v 1.11 2019/12/01 16:33:33 tkusumi Exp $      */
 
 /*
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -29,7 +29,7 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: dm_pdev.c,v 1.10 2018/01/05 14:22:26 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: dm_pdev.c,v 1.11 2019/12/01 16:33:33 tkusumi Exp $");
 
 #include <sys/types.h>
 #include <sys/param.h>
@@ -103,15 +103,17 @@
                mutex_exit(&dm_pdev_mutex);
                return dmp;
        }
-       mutex_exit(&dm_pdev_mutex);
 
-       if ((dmp = dm_pdev_alloc(dev_name)) == NULL)
+       if ((dmp = dm_pdev_alloc(dev_name)) == NULL) {
+               mutex_exit(&dm_pdev_mutex);
                return NULL;
+       }
 
        dev_pb = pathbuf_create(dev_name);
        if (dev_pb == NULL) {
                aprint_debug("%s: pathbuf_create on device: %s failed!\n",
                    __func__, dev_name);
+               mutex_exit(&dm_pdev_mutex);
                kmem_free(dmp, sizeof(dm_pdev_t));
                return NULL;
        }
@@ -120,13 +122,13 @@
        if (error) {
                aprint_debug("%s: dk_lookup on device: %s (error %d)\n",
                    __func__, dev_name, error);
+               mutex_exit(&dm_pdev_mutex);
                kmem_free(dmp, sizeof(dm_pdev_t));
                return NULL;
        }
        getdisksize(dmp->pdev_vnode, &dmp->pdev_numsec, &dmp->pdev_secsize);
        dmp->ref_cnt = 1;
 
-       mutex_enter(&dm_pdev_mutex);
        SLIST_INSERT_HEAD(&dm_pdev_list, dmp, next_pdev);
        mutex_exit(&dm_pdev_mutex);