Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Chengguang Xu <cgxu519@mykernel.net>
To:     ericvh@gmail.com, lucho@ionkov.net, asmadeus@codewreck.org
Cc:     v9fs-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org,
        Chengguang Xu <cgxu519@mykernel.net>
Message-ID: <20201205130904.518104-1-cgxu519@mykernel.net>
Subject: [RFC PATCH] 9p: create writeback fid on shared mmap
Date:   Sat,  5 Dec 2020 21:09:04 +0800
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset=utf8
Precedence: bulk

If vma is shared and the file was opened for writing,
we should also create writeback fid because vma may be
mprotected writable even if now readonly.

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
---
Caveat: Only compile tested.

 fs/9p/vfs_file.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index b177fd3b1eb3..791839c2dd5c 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -516,8 +516,7 @@ v9fs_mmap_file_mmap(struct file *filp, struct vm_area_s=
truct *vma)
 =09v9inode =3D V9FS_I(inode);
 =09mutex_lock(&v9inode->v_mutex);
 =09if (!v9inode->writeback_fid &&
-=09    (vma->vm_flags & VM_SHARED) &&
-=09    (vma->vm_flags & VM_WRITE)) {
+=09    mapping_writably_mapped(filp->f_mapping)) {
 =09=09/*
 =09=09 * clone a fid and add it to writeback_fid
 =09=09 * we do it during mmap instead of
--=20
2.26.2