linux-kernel - Re: [RFC 3/4] nbd: Create helper functions for ioctls

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Date:	Wed, 28 Jan 2015 16:04:28 -0500
From:	Paul Clements <paul.clements@...sios.com>
To:	Markus Pargmann <mpa@...gutronix.de>
Cc:	"nbd-general@...ts.sourceforge.net" 
	<nbd-general@...ts.sourceforge.net>,
	kernel list <linux-kernel@...r.kernel.org>,
	kernel@...gutronix.de
Subject: Re: [RFC 3/4] nbd: Create helper functions for ioctls

Markus,

Comments below...

On Tue, Jan 13, 2015 at 8:44 AM, Markus Pargmann <mpa@...gutronix.de> wrote:
> This patch prepares the nbd code for the nbd-root device patch. It
> moves the ioctl code into separate functions so they can be called
> directly. The patch creates nbd_set_total_size(), nbd_set_blksize(),
> nbd_set_sock() and nbd_set_timeout().
>
> Signed-off-by: Markus Pargmann <mpa@...gutronix.de>
> ---
>  drivers/block/nbd.c | 79 ++++++++++++++++++++++++++++++++++++++---------------
>  1 file changed, 57 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 0ff6ebbec252..11f7644be111 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -596,6 +596,55 @@ static void do_nbd_request(struct request_queue *q)
>         }
>  }
>
> +/*
> + * Call with tx_lock held
> + */
> +static void nbd_set_total_size(struct block_device *bdev,
> +                              struct nbd_device *nbd, size_t size)
> +{
> +       nbd->bytesize = size;
> +       bdev->bd_inode->i_size = size;
> +       set_blocksize(bdev, nbd->blksize);
> +       set_capacity(nbd->disk, size >> 9);
> +}
> +
> +/*
> + * Call with tx_lock held
> + */
> +static void nbd_set_blksize(struct block_device *bdev, struct nbd_device *nbd,
> +                           size_t blksize)
> +{
> +       u64 new_bytesize;
> +
> +       nbd->blksize = blksize;
> +       bdev->bd_inode->i_size = nbd->bytesize;
> +       set_blocksize(bdev, nbd->blksize);
> +
> +       new_bytesize = nbd->bytesize & ~(nbd->blksize-1);
> +       if (new_bytesize != nbd->bytesize)
> +               nbd_set_total_size(bdev, nbd, new_bytesize);

could just do set_capacity here to save a few cycles, but not a big
deal either way...


> +}
> +
> +/*
> + * Call with tx_lock held
> + */
> +static void nbd_set_sock(struct block_device *bdev, struct nbd_device *nbd,
> +                        struct socket *sock)
> +{
> +       nbd->sock = sock;
> +       if (max_part > 0)
> +               bdev->bd_invalidated = 1;
> +       nbd->disconnect = 0; /* we're connected now */
> +}
> +
> +/*
> + * Call with tx_lock held
> + */
> +static void nbd_set_timeout(struct nbd_device *nbd, int timeout)
> +{
> +       nbd->xmit_timeout = timeout * HZ;
> +}
> +
>  static int nbd_connection_start(struct block_device *bdev,
>                                 struct nbd_device *nbd)
>  {
> @@ -733,33 +782,22 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
>                 if (nbd->sock)
>                         return -EBUSY;
>                 sock = sockfd_lookup(arg, &err);
> -               if (sock) {
> -                       nbd->sock = sock;
> -                       if (max_part > 0)
> -                               bdev->bd_invalidated = 1;
> -                       nbd->disconnect = 0; /* we're connected now */
> -                       return 0;
> -               }
> -               return -EINVAL;
> +               if (!sock)
> +                       return -EINVAL;
> +
> +               nbd_set_sock(bdev, nbd, sock);

need a return 0 here


>         }
>
>         case NBD_SET_BLKSIZE:
> -               nbd->blksize = arg;
> -               nbd->bytesize &= ~(nbd->blksize-1);
> -               bdev->bd_inode->i_size = nbd->bytesize;
> -               set_blocksize(bdev, nbd->blksize);
> -               set_capacity(nbd->disk, nbd->bytesize >> 9);
> +               nbd_set_blksize(bdev, nbd, arg);
>                 return 0;
>
>         case NBD_SET_SIZE:
> -               nbd->bytesize = arg & ~(nbd->blksize-1);
> -               bdev->bd_inode->i_size = nbd->bytesize;
> -               set_blocksize(bdev, nbd->blksize);
> -               set_capacity(nbd->disk, nbd->bytesize >> 9);
> +               nbd_set_total_size(bdev, nbd, arg & ~(nbd->blksize-1));
>                 return 0;

Might consider deprecating this one...it's pretty useless these days,
as it has the same function as NBD_SET_SIZE_BLOCKS, but has a smaller
device size limit (at least on some platforms)... nbd-client does not
use it anymore...


>         case NBD_SET_TIMEOUT:
> -               nbd->xmit_timeout = arg * HZ;
> +               nbd_set_timeout(nbd, arg);
>                 return 0;
>
>         case NBD_SET_FLAGS:
> @@ -767,10 +805,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
>                 return 0;
>
>         case NBD_SET_SIZE_BLOCKS:
> -               nbd->bytesize = ((u64) arg) * nbd->blksize;
> -               bdev->bd_inode->i_size = nbd->bytesize;
> -               set_blocksize(bdev, nbd->blksize);
> -               set_capacity(nbd->disk, nbd->bytesize >> 9);
> +               nbd_set_total_size(bdev, nbd, ((u64)arg) * nbd->blksize);
>                 return 0;
>
>         case NBD_DO_IT:
--
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