Am 12.10.2018 um 19:02 hat Eric Blake geschrieben:
> On 10/12/18 6:55 AM, Kevin Wolf wrote:
> > Some block drivers have traditionally changed their node to read-only
> > mode without asking the user. This behaviour has been marked deprecated
> > since 2.11, expecting users to provide an explicit read-only=on option.
> >
> > Now that we have auto-read-only=on, enable these drivers to make use of
> > the option.
> >
> > This is the only use of bdrv_set_read_only(), so we can make it a bit
> > more specific and turn it into a bdrv_apply_auto_read_only() that is
> > more convenient for drivers to use.
> >
> > Signed-off-by: Kevin Wolf <kw...@redhat.com>
> > ---
>
> > +++ b/block.c
> > @@ -266,27 +266,36 @@ int bdrv_can_set_read_only(BlockDriverState *bs, bool
> > read_only,
> > return 0;
> > }
> > -/* TODO Remove (deprecated since 2.11)
> > - * Block drivers are not supposed to automatically change bs->read_only.
> > - * Instead, they should just check whether they can provide what the user
> > - * explicitly requested and error out if read-write is requested, but they
> > can
> > - * only provide read-only access. */
> > -int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp)
> > +/*
> > + * Called by a driver that can only provide a read-only image.
> > + *
> > + * Returns 0 if the node is already read-only or it could switch the node
> > to
> > + * read-only because BDRV_O_AUTO_RDONLY is set.
> > + *
> > + * Returns -EACCES if the node is read-write and BDRV_O_AUTO_RDONLY is not
> > set.
> > + * If @errmsg is not NULL, it is used as the error message for the Error
> > + * object.
>
> I like it.
>
> Worth documenting the -EINVAL (copy-on-read prevents setting read-only)
> failure as well? (The -EPERM failure of bdrv_can_set_read_only() is not
> reachable, since this new function never clears readonly).
In fact, -EINVAL and the error string from bdrv_can_set_read_only() may
be confusing because the user didn't explicitly request a read-only
image. Maybe it would be better to just turn this case into -EACCES with
the same error message.
What do you think?
> > + */
> > +int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,
> > + Error **errp)
> > {
> > int ret = 0;
> > - ret = bdrv_can_set_read_only(bs, read_only, false, errp);
> > + if (!(bs->open_flags & BDRV_O_RDWR)) {
> > + return 0;
> > + }
> > + if (!(bs->open_flags & BDRV_O_AUTO_RDONLY)) {
> > + error_setg(errp, "%s", errmsg ?: "Image is read-only");
> > + return -EACCES;
> > + }
> > +
> > + ret = bdrv_can_set_read_only(bs, true, false, errp);
> > if (ret < 0) {
> > return ret;
> > }
>
> Makes sense.
>
> > +++ b/block/vvfat.c
> > @@ -1262,16 +1262,10 @@ static int vvfat_open(BlockDriverState *bs, QDict
> > *options, int flags,
> > "Unable to set VVFAT to 'rw' when drive is
> > read-only");
> > goto fail;
> > }
> > - } else if (!bdrv_is_read_only(bs)) {
> > - error_report("Opening non-rw vvfat images without an explicit "
> > - "read-only=on option is deprecated. Future versions "
> > - "will refuse to open the image instead of "
> > - "automatically marking the image read-only.");
> > - /* read only is the default for safety */
> > - ret = bdrv_set_read_only(bs, true, &local_err);
> > + } else {
> > + ret = bdrv_apply_auto_read_only(bs, NULL, errp);
> > if (ret < 0) {
> > - error_propagate(errp, local_err);
> > - goto fail;
> > + return ret;
>
> Don't you still need the goto fail, to avoid leaking opts?
Yes, I do. Thanks.
Kevin
