Re: [PATCH] xen-blkback: convert hole punching to discard request on loop devices

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Nov 07, 2011 at 04:34:26PM +0800, Li Dongyang wrote:
> As of dfaa2ef68e80c378e610e3c8c536f1c239e8d3ef, loop devices support
> discard request now. We could just issue a discard request, and
> the loop driver will punch the hole for us, so we don't need to touch
> the internals of loop device and punch the hole ourselves, Thanks.

Can I ask you to do two things:
 1). Look in whether we can just eliminate the BLKIF_BACKEND_FILE altogether?
 2). Rebase this on top #devel/for-jens-3.3 (git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git)

Thanks!
> 
> Signed-off-by: Li Dongyang <lidongyang@novell.com>
> ---
>  drivers/block/xen-blkback/blkback.c |   21 +++------------------
>  1 files changed, 3 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
> index 15ec4db..ad365a7 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -39,9 +39,6 @@
>  #include <linux/list.h>
>  #include <linux/delay.h>
>  #include <linux/freezer.h>
> -#include <linux/loop.h>
> -#include <linux/falloc.h>
> -#include <linux/fs.h>
>  
>  #include <xen/events.h>
>  #include <xen/page.h>
> @@ -422,25 +419,13 @@ static void xen_blk_discard(struct xen_blkif *blkif, struct blkif_request *req)
>  	int status = BLKIF_RSP_OKAY;
>  	struct block_device *bdev = blkif->vbd.bdev;
>  
> -	if (blkif->blk_backend_type == BLKIF_BACKEND_PHY)
> -		/* just forward the discard request */
> +	if (blkif->blk_backend_type == BLKIF_BACKEND_PHY ||
> +	    blkif->blk_backend_type == BLKIF_BACKEND_FILE)
>  		err = blkdev_issue_discard(bdev,
>  				req->u.discard.sector_number,
>  				req->u.discard.nr_sectors,
>  				GFP_KERNEL, 0);
> -	else if (blkif->blk_backend_type == BLKIF_BACKEND_FILE) {
> -		/* punch a hole in the backing file */
> -		struct loop_device *lo = bdev->bd_disk->private_data;
> -		struct file *file = lo->lo_backing_file;
> -
> -		if (file->f_op->fallocate)
> -			err = file->f_op->fallocate(file,
> -				FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE,
> -				req->u.discard.sector_number << 9,
> -				req->u.discard.nr_sectors << 9);
> -		else
> -			err = -EOPNOTSUPP;
> -	} else
> +	else
>  		err = -EOPNOTSUPP;
>  
>  	if (err == -EOPNOTSUPP) {
> -- 
> 1.7.7
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel