From ee965dfa64929227ced8adb68900c35f877480e7 Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Wed, 3 Feb 2021 13:02:18 +0200
Subject: [PATCH] vn_open(): If the vnode is reclaimed during open(2), do not
 return error.

Most future operations on the returned file descriptor will fail
anyway, and application should be ready to handle that failures.  Not
forcing it to understand the transient failure mode on open, which is
implementation-specific, should make us less special without loss of
reporting of errors.

Suggested by: chs
Reviewed by:	chs, mckusick
Tested by:	pho
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
---
 sys/fs/deadfs/dead_vnops.c | 11 +++++++++--
 sys/kern/vfs_vnops.c       |  2 --
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/sys/fs/deadfs/dead_vnops.c b/sys/fs/deadfs/dead_vnops.c
index 09c3c996ee0..324bbafd7ca 100644
--- a/sys/fs/deadfs/dead_vnops.c
+++ b/sys/fs/deadfs/dead_vnops.c
@@ -45,6 +45,7 @@
  */
 static vop_lookup_t	dead_lookup;
 static vop_open_t	dead_open;
+static vop_close_t	dead_close;
 static vop_getwritemount_t dead_getwritemount;
 static vop_rename_t	dead_rename;
 static vop_unset_text_t	dead_unset_text;
@@ -55,6 +56,7 @@ struct vop_vector dead_vnodeops = {
 	.vop_access =		VOP_EBADF,
 	.vop_advlock =		VOP_EBADF,
 	.vop_bmap =		VOP_EBADF,
+	.vop_close =		dead_close,
 	.vop_create =		VOP_PANIC,
 	.vop_getattr =		VOP_EBADF,
 	.vop_getwritemount =	dead_getwritemount,
@@ -104,13 +106,18 @@ dead_lookup(struct vop_lookup_args *ap)
 }
 
 /*
- * Open always fails as if device did not exist.
+ * Silently succeed open and close.
  */
 static int
 dead_open(struct vop_open_args *ap)
 {
+	return (0);
+}
 
-	return (ENXIO);
+static int
+dead_close(struct vop_close_args *ap)
+{
+	return (0);
 }
 
 int
diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index 6c6727c7f37..f70bcdab420 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -356,8 +356,6 @@ vn_open_vnode_advlock(struct vnode *vp, int fmode, struct file *fp)
 		fp->f_flag |= FHASLOCK;
 
 	vn_lock(vp, lock_flags | LK_RETRY);
-	if (error == 0 && VN_IS_DOOMED(vp))
-		error = ENOENT;
 	return (error);
 }