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Re: [Qemu-devel] [RFC/PATCH] virtio-9p: Add Read only support for 9p exp
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [RFC/PATCH] virtio-9p: Add Read only support for 9p export. |
Date: |
Mon, 23 May 2011 11:08:34 +0100 |
On Mon, May 23, 2011 at 8:58 AM, M. Mohan Kumar <address@hidden> wrote:
> A new fsdev parameter "access" is introduced to control accessing 9p export.
> access=ro|rw can be used to specify the access type. By default rw access
> is given to 9p export.
It would be consistent with -drive to use readonly=on|off (default:
off). Do you have any future access modes in mind that require more
than readonly on|off?
It seems the client does not know ahead of time that the mount is
read-only. I wonder if this exposes any weirdness compared to
actually mounting ro on the client side (i.e. operations that appear
to start okay but then fail with -EROFS at a different point than if
you had mounted ro)? It could cause apps to error in new ways.
> +static inline int is_ro_export(FsContext *fs_ctx)
> +{
> + if (fs_ctx->flags & FS_RDONLY) {
> + return 1;
> + }
> + return 0;
> +}
Please use bool and fix indentation:
static inline bool is_ro_export(FsContext *fs_ctx)
{
return fs_ctx->flags & FS_RDONLY;
}
> +
> static void v9fs_version(V9fsState *s, V9fsPDU *pdu)
> {
> V9fsString version;
> @@ -1734,6 +1742,13 @@ static void v9fs_open_post_lstat(V9fsState *s,
> V9fsOpenState *vs, int err)
> vs->fidp->fs.dir = v9fs_do_opendir(s, &vs->fidp->path);
> v9fs_open_post_opendir(s, vs, err);
> } else {
> + if (is_ro_export(&s->ctx)) {
> + if (vs->mode & O_WRONLY || vs->mode & O_RDWR ||
> + vs->mode & O_APPEND) {
> + err = -EROFS;
> + goto out;
> + }
> + }
> if (s->proto_version == V9FS_PROTO_2000L) {
> flags = vs->mode;
> flags &= ~(O_NOCTTY | O_ASYNC | O_CREAT);
> @@ -3606,6 +3621,33 @@ static pdu_handler_t *pdu_handlers[] = {
> [P9_TREMOVE] = v9fs_remove,
> };
>
> +static inline int is_read_only_op(int id)
bool
Stefan