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

[Li Dongyang <lidongyang@xxxxxxxxxx>]

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.

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) {
-- 
1.7.7


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