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[Xen-devel] [PATCH V2 3/3] xen-blkback: handle trim request in backend d

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] [PATCH V2 3/3] xen-blkback: handle trim request in backend driver
From: Li Dongyang <lidongyang@xxxxxxxxxx>
Date: Thu, 18 Aug 2011 17:34:31 +0800
Cc: owen.smith@xxxxxxxxxx, JBeulich@xxxxxxxxxx
Delivery-date: Thu, 18 Aug 2011 02:38:13 -0700
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Now blkback driver can handle the trim request from guest, we will
forward the request to phy device if it really has trim support, or we'll
punch a hole on the image file.

Signed-off-by: Li Dongyang <lidongyang@xxxxxxxxxx>
---
 drivers/block/xen-blkback/blkback.c |   85 +++++++++++++++++++++++++++++------
 drivers/block/xen-blkback/common.h  |    4 +-
 drivers/block/xen-blkback/xenbus.c  |   61 +++++++++++++++++++++++++
 3 files changed, 135 insertions(+), 15 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c 
b/drivers/block/xen-blkback/blkback.c
index 2330a9a..5acc37a 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -39,6 +39,9 @@
 #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>
@@ -258,13 +261,16 @@ irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
 
 static void print_stats(struct xen_blkif *blkif)
 {
-       pr_info("xen-blkback (%s): oo %3d  |  rd %4d  |  wr %4d  |  f %4d\n",
+       pr_info("xen-blkback (%s): oo %3d  |  rd %4d  |  wr %4d  |  f %4d"
+                "  |  tr %4d\n",
                 current->comm, blkif->st_oo_req,
-                blkif->st_rd_req, blkif->st_wr_req, blkif->st_f_req);
+                blkif->st_rd_req, blkif->st_wr_req,
+                blkif->st_f_req, blkif->st_tr_req);
        blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000);
        blkif->st_rd_req = 0;
        blkif->st_wr_req = 0;
        blkif->st_oo_req = 0;
+       blkif->st_tr_req = 0;
 }
 
 int xen_blkif_schedule(void *arg)
@@ -563,6 +569,10 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
                blkif->st_f_req++;
                operation = WRITE_FLUSH;
                break;
+       case BLKIF_OP_TRIM:
+               blkif->st_tr_req++;
+               operation = REQ_DISCARD;
+               break;
        case BLKIF_OP_WRITE_BARRIER:
        default:
                operation = 0; /* make gcc happy */
@@ -572,7 +582,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 
        /* Check that the number of segments is sane. */
        nseg = req->nr_segments;
-       if (unlikely(nseg == 0 && operation != WRITE_FLUSH) ||
+       if (unlikely(nseg == 0 && operation != (WRITE_FLUSH | REQ_DISCARD)) ||
            unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
                pr_debug(DRV_PFX "Bad number of segments in request (%d)\n",
                         nseg);
@@ -627,10 +637,13 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
         * the hypercall to unmap the grants - that is all done in
         * xen_blkbk_unmap.
         */
-       if (xen_blkbk_map(req, pending_req, seg))
+       if (operation != BLKIF_OP_TRIM && xen_blkbk_map(req, pending_req, seg))
                goto fail_flush;
 
-       /* This corresponding xen_blkif_put is done in __end_block_io_op */
+       /*
+        * This corresponding xen_blkif_put is done in __end_block_io_op, or
+        * below if we are handling a BLKIF_OP_TRIM.
+        */
        xen_blkif_get(blkif);
 
        for (i = 0; i < nseg; i++) {
@@ -654,18 +667,62 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
                preq.sector_number += seg[i].nsec;
        }
 
-       /* This will be hit if the operation was a flush. */
+       /* This will be hit if the operation was a flush or trim. */
        if (!bio) {
-               BUG_ON(operation != WRITE_FLUSH);
+               BUG_ON(operation != (WRITE_FLUSH | REQ_DISCARD));
 
-               bio = bio_alloc(GFP_KERNEL, 0);
-               if (unlikely(bio == NULL))
-                       goto fail_put_bio;
+               if (operation == WRITE_FLUSH) {
+                       bio = bio_alloc(GFP_KERNEL, 0);
+                       if (unlikely(bio == NULL))
+                               goto fail_put_bio;
 
-               biolist[nbio++] = bio;
-               bio->bi_bdev    = preq.bdev;
-               bio->bi_private = pending_req;
-               bio->bi_end_io  = end_block_io_op;
+                       biolist[nbio++] = bio;
+                       bio->bi_bdev    = preq.bdev;
+                       bio->bi_private = pending_req;
+                       bio->bi_end_io  = end_block_io_op;
+               } else if (operation == REQ_DISCARD) {
+                       int err = 0;
+                       int status = BLKIF_RSP_OKAY;
+                       struct block_device *bdev = blkif->vbd.bdev;
+
+                       preq.nr_sects = req->u.trim.nr_sectors;
+                       if (blkif->vbd.type & VDISK_PHY_BACKEND)
+                               /* just forward the trim request */
+                               err = blkdev_issue_discard(bdev,
+                                               preq.sector_number,
+                                               preq.nr_sects,
+                                               GFP_KERNEL, 0);
+                       else if (blkif->vbd.type & VDISK_FILE_BACKEND) {
+                               /* 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,
+                                               preq.sector_number << 9,
+                                               preq.nr_sects << 9);
+                               else
+                                       err = -EOPNOTSUPP;
+                       } else
+                               status = BLKIF_RSP_EOPNOTSUPP;
+
+                       if (err == -EOPNOTSUPP) {
+                               DPRINTK("blkback: discard op failed, "
+                                               "not supported\n");
+                               status = BLKIF_RSP_EOPNOTSUPP;
+                       } else if (err)
+                               status = BLKIF_RSP_ERROR;
+
+                       if (status == BLKIF_RSP_OKAY)
+                               blkif->st_tr_sect += preq.nr_sects;
+                       make_response(blkif, req->id, req->operation, status);
+                       xen_blkif_put(blkif);
+                       free_req(pending_req);
+                       return 0;
+               }
        }
 
        /*
diff --git a/drivers/block/xen-blkback/common.h 
b/drivers/block/xen-blkback/common.h
index 9e40b28..1fef727 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -159,8 +159,10 @@ struct xen_blkif {
        int                     st_wr_req;
        int                     st_oo_req;
        int                     st_f_req;
+       int                     st_tr_req;
        int                     st_rd_sect;
        int                     st_wr_sect;
+       int                     st_tr_sect;
 
        wait_queue_head_t       waiting_to_free;
 
@@ -182,7 +184,7 @@ struct xen_blkif {
 
 struct phys_req {
        unsigned short          dev;
-       unsigned short          nr_sects;
+       blkif_sector_t          nr_sects;
        struct block_device     *bdev;
        blkif_sector_t          sector_number;
 };
diff --git a/drivers/block/xen-blkback/xenbus.c 
b/drivers/block/xen-blkback/xenbus.c
index 3f129b4..05ea8e0 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -272,16 +272,20 @@ VBD_SHOW(oo_req,  "%d\n", be->blkif->st_oo_req);
 VBD_SHOW(rd_req,  "%d\n", be->blkif->st_rd_req);
 VBD_SHOW(wr_req,  "%d\n", be->blkif->st_wr_req);
 VBD_SHOW(f_req,  "%d\n", be->blkif->st_f_req);
+VBD_SHOW(tr_req, "%d\n", be->blkif->st_tr_req);
 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
+VBD_SHOW(tr_sect, "%d\n", be->blkif->st_tr_sect);
 
 static struct attribute *xen_vbdstat_attrs[] = {
        &dev_attr_oo_req.attr,
        &dev_attr_rd_req.attr,
        &dev_attr_wr_req.attr,
        &dev_attr_f_req.attr,
+       &dev_attr_tr_req.attr,
        &dev_attr_rd_sect.attr,
        &dev_attr_wr_sect.attr,
+       &dev_attr_tr_sect.attr,
        NULL
 };
 
@@ -419,6 +423,59 @@ int xen_blkbk_flush_diskcache(struct xenbus_transaction 
xbt,
        return err;
 }
 
+int xen_blkbk_trim(struct xenbus_transaction xbt, struct backend_info *be)
+{
+       struct xenbus_device *dev = be->dev;
+       struct xen_vbd *vbd = &be->blkif->vbd;
+       char *type;
+       int err;
+       int state = 0;
+
+       type = xenbus_read(XBT_NIL, dev->nodename, "type", NULL);
+       if (!IS_ERR(type)) {
+               if (strcmp(type, "file") == 0)
+                       state = 1;
+                       vbd->type |= VDISK_FILE_BACKEND;
+               if (strcmp(type, "phy") == 0) {
+                       struct block_device *bdev = be->blkif->vbd.bdev;
+                       struct request_queue *q = bdev_get_queue(bdev);
+                       if (blk_queue_discard(q)) {
+                               err = xenbus_printf(xbt, dev->nodename,
+                                       "discard_granularity", "%u",
+                                       q->limits.discard_granularity);
+                               if (err) {
+                                       xenbus_dev_fatal(dev, err,
+                                               "writing discard_granularity");
+                                       goto kfree;
+                               }
+                               err = xenbus_printf(xbt, dev->nodename,
+                                       "discard_alignment", "%u",
+                                       q->limits.discard_alignment);
+                               if (err) {
+                                       xenbus_dev_fatal(dev, err,
+                                               "writing discard_alignment");
+                                       goto kfree;
+                               }
+                               state = 1;
+                               vbd->type |= VDISK_PHY_BACKEND;
+                       }
+               }
+       } else {
+               err = PTR_ERR(type);
+               xenbus_dev_fatal(dev, err, "reading type");
+               goto out;
+       }
+
+       err = xenbus_printf(xbt, dev->nodename, "feature-trim",
+                           "%d", state);
+       if (err)
+               xenbus_dev_fatal(dev, err, "writing feature-trim");
+kfree:
+       kfree(type);
+out:
+       return err;
+}
+
 /*
  * Entry point to this code when a new device is created.  Allocate the basic
  * structures, and watch the store waiting for the hotplug scripts to tell us
@@ -650,6 +707,10 @@ again:
        if (err)
                goto abort;
 
+       err = xen_blkbk_trim(xbt, be);
+       if (err)
+               goto abort;
+
        err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
                            (unsigned long long)vbd_sz(&be->blkif->vbd));
        if (err) {
-- 
1.7.6


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