>>> On 07.11.11 at 09:34, Li Dongyang <lidongyang@xxxxxxxxxx> 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.
Looking at what the loop driver now does - doesn't the original code
here lack support for lo_offset being non-zero then? If so, should we
fix this in pre-3.2 kernels?
Jan
> Signed-off-by: Li Dongyang <lidongyang@xxxxxxxxxx>
> ---
> 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) {
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