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mount_9p: fix writing to a file opened with write-only mode 

With the page cache, writing data to a file may demand to read contents
from a storage to fill a page in the page cache first.

Opening a file with write-only mode by a user lets a mount_9p process
open a file with write-only mode too at a 9p server.  Thus, a read
request to the file from the page cache fails.

So we need to open a file always with read mode (internally) even if it
is opened with write-only mode by a user.

Note that the change doesn't mean that mount_9p allows users to read
contents from a file that is opened with write-only mode.
This commit is contained in:
ozaki-r 2022-03-02 04:11:41 +00:00
parent 08a9f63190
commit ab2dc16550
1 changed files with 4 additions and 2 deletions
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6
usr.sbin/puffs/mount_9p/node.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: node.c,v 1.29 2020/06/01 13:30:52 uwe Exp $ */
/* $NetBSD: node.c,v 1.30 2022/03/02 04:11:41 ozaki-r Exp $ */
/*
* Copyright (c) 2007 Antti Kantee. All Rights Reserved.
@ -27,7 +27,7 @@
#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: node.c,v 1.29 2020/06/01 13:30:52 uwe Exp $");
__RCSID("$NetBSD: node.c,v 1.30 2022/03/02 04:11:41 ozaki-r Exp $");
#endif /* !lint */
#include <assert.h>
@ -274,6 +274,8 @@ puffs9p_node_open(struct puffs_usermount *pu, void *opc, int mode,
puffs_setback(pcc, PUFFS_SETBACK_INACT_N1);
if (pn->pn_va.va_type != VDIR) {
/* Always require read access for page cache */
mode |= FREAD;
if (mode & FREAD && p9n->fid_read == P9P_INVALFID) {
nfid = NEXTFID(p9p);
error = proto_cc_open(pu, p9n->fid_base, nfid,