Re: [RFC PATCH v4 4/5] btrfs: ioctl: introduce btrfs_uring_import_iovec()

[Sidong Yang <sidong.yang@furiosa.ai>]

On Mon, Mar 17, 2025 at 09:40:05AM -0600, Jens Axboe wrote:
> On 3/17/25 7:57 AM, Sidong Yang wrote:
> > This patch introduces btrfs_uring_import_iovec(). In encoded read/write
> > with uring cmd, it uses import_iovec without supporting fixed buffer.
> > btrfs_using_import_iovec() could use fixed buffer if cmd flags has
> > IORING_URING_CMD_FIXED.
> > 
> > Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> > ---
> >  fs/btrfs/ioctl.c | 32 ++++++++++++++++++++++++--------
> >  1 file changed, 24 insertions(+), 8 deletions(-)
> > 
> > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> > index 6c18bad53cd3..a7b52fd99059 100644
> > --- a/fs/btrfs/ioctl.c
> > +++ b/fs/btrfs/ioctl.c
> > @@ -4802,6 +4802,28 @@ struct btrfs_uring_encoded_data {
> >  	struct iov_iter iter;
> >  };
> >  
> > +static int btrfs_uring_import_iovec(struct io_uring_cmd *cmd,
> > +				    unsigned int issue_flags, int rw)
> > +{
> > +	struct btrfs_uring_encoded_data *data =
> > +		io_uring_cmd_get_async_data(cmd)->op_data;
> > +	int ret;
> > +
> > +	if (cmd && (cmd->flags & IORING_URING_CMD_FIXED)) {
> > +		data->iov = NULL;
> > +		ret = io_uring_cmd_import_fixed_vec(cmd, data->args.iov,
> > +						    data->args.iovcnt,
> > +						    ITER_DEST, issue_flags,
> > +						    &data->iter);
> > +	} else {
> > +		data->iov = data->iovstack;
> > +		ret = import_iovec(rw, data->args.iov, data->args.iovcnt,
> > +				   ARRAY_SIZE(data->iovstack), &data->iov,
> > +				   &data->iter);
> > +	}
> > +	return ret;
> > +}
> 
> How can 'cmd' be NULL here?

It seems that there is no checkes for 'cmd' before and it works same as before.
But I think it's better to add a check in function start for safety.

> 
> 
> -- 
> Jens Axboe
>