From: mjg <mjg@FreeBSD.org>
Date: Tue, 17 Sep 2019 15:53:40 +0000 (+0000)
Subject: vfs: apply r352437 to the fast path as well
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=b6dddc83dd6054edeb98f7730d784719c4584d67;p=freebsd.git

vfs: apply r352437 to the fast path as well

This one is very hard to run into. If the filesystem is being unmounted or
the mount point is freed the vfs_op_thread_enter will fail. For it to
succeed the mount point itself would have to be reallocated in the time
window between the initial read and the attempt to enter.

Sponsored by:	The FreeBSD Foundation
---

diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c
index 2fd95fbc8b4..8aee8abfbe7 100644
--- a/sys/kern/vfs_default.c
+++ b/sys/kern/vfs_default.c
@@ -606,11 +606,13 @@ vop_stdgetwritemount(ap)
 		return (0);
 	}
 	if (vfs_op_thread_enter(mp)) {
-		if (mp == vp->v_mount)
+		if (mp == vp->v_mount) {
 			vfs_mp_count_add_pcpu(mp, ref, 1);
-		else
+			vfs_op_thread_exit(mp);
+		} else {
+			vfs_op_thread_exit(mp);
 			mp = NULL;
-		vfs_op_thread_exit(mp);
+		}
 	} else {
 		MNT_ILOCK(mp);
 		if (mp == vp->v_mount) {