xen-blkback: convert hole punching to discard request on loop devices

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.

V0->V1: rebased on devel/for-jens-3.3

Signed-off-by: Li Dongyang <lidongyang@novell.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index b058de7..0088bf6 100644 (file)
--- 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>
@@ -426,27 +423,15 @@ static int dispatch_discard_io(struct xen_blkif *blkif,
        blkif->st_ds_req++;
 
        xen_blkif_get(blkif);
-       if (blkif->blk_backend_type == BLKIF_BACKEND_PHY) {
+       if (blkif->blk_backend_type == BLKIF_BACKEND_PHY ||
+           blkif->blk_backend_type == BLKIF_BACKEND_FILE) {
                unsigned long secure = (blkif->vbd.discard_secure &&
                        (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
                        BLKDEV_DISCARD_SECURE : 0;
-               /* just forward the discard request */
                err = blkdev_issue_discard(bdev,
                                req->u.discard.sector_number,
                                req->u.discard.nr_sectors,
                                GFP_KERNEL, secure);
-       } 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
                err = -EOPNOTSUPP;