3 files changed, 206 insertions, 31 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 2330a9ad5e9..9713d5a490e 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"
+                 "  |  ds %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_ds_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_ds_req = 0;
 }
 
 int xen_blkif_schedule(void *arg)
@@ -410,6 +416,42 @@ static int xen_blkbk_map(struct blkif_request *req,
         return ret;
 }
 
+static void xen_blk_discard(struct xen_blkif *blkif, struct blkif_request *req)
+{
+        int err = 0;
+        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 */
+                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
+                err = -EOPNOTSUPP;
+
+        if (err == -EOPNOTSUPP) {
+                pr_debug(DRV_PFX "discard op failed, not supported\n");
+                status = BLKIF_RSP_EOPNOTSUPP;
+        } else if (err)
+                status = BLKIF_RSP_ERROR;
+
+        make_response(blkif, req->id, req->operation, status);
+}
+
 /*
  * Completion callback on the bio's. Called as bh->b_end_io()
  */
@@ -563,6 +605,10 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
                 blkif->st_f_req++;
                 operation = WRITE_FLUSH;
                 break;
+        case BLKIF_OP_DISCARD:
+                blkif->st_ds_req++;
+                operation = REQ_DISCARD;
+                break;
         case BLKIF_OP_WRITE_BARRIER:
         default:
                 operation = 0; /* make gcc happy */
@@ -572,7 +618,8 @@ 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 &&
+                                operation != REQ_DISCARD) ||
             unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
                 pr_debug(DRV_PFX "Bad number of segments in request (%d)\n",
                          nseg);
@@ -627,10 +674,14 @@ 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_DISCARD &&
+                        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 (in "!bio") if we are handling a BLKIF_OP_DISCARD.
+         */
         xen_blkif_get(blkif);
 
         for (i = 0; i < nseg; i++) {
@@ -654,18 +705,25 @@ 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 discard. */
         if (!bio) {
-                BUG_ON(operation != WRITE_FLUSH);
+                BUG_ON(operation != WRITE_FLUSH && operation != 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) {
+                        xen_blk_discard(blkif, req);
+                        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 9e40b283a46..bfb532ea5b1 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -63,13 +63,26 @@ struct blkif_common_response {
 
 /* i386 protocol version */
 #pragma pack(push, 4)
+
+struct blkif_x86_32_request_rw {
+        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
+        struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+};
+
+struct blkif_x86_32_request_discard {
+        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
+        uint64_t nr_sectors;
+};
+
 struct blkif_x86_32_request {
         uint8_t        operation;    /* BLKIF_OP_???                         */
         uint8_t        nr_segments;  /* number of segments                   */
         blkif_vdev_t   handle;       /* only for read/write requests         */
         uint64_t       id;           /* private guest value, echoed in resp  */
-        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
-        struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+        union {
+                struct blkif_x86_32_request_rw rw;
+                struct blkif_x86_32_request_discard discard;
+        } u;
 };
 struct blkif_x86_32_response {
         uint64_t        id;              /* copied from request */
@@ -79,13 +92,26 @@ struct blkif_x86_32_response {
 #pragma pack(pop)
 
 /* x86_64 protocol version */
+
+struct blkif_x86_64_request_rw {
+        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
+        struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+};
+
+struct blkif_x86_64_request_discard {
+        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
+        uint64_t nr_sectors;
+};
+
 struct blkif_x86_64_request {
         uint8_t        operation;    /* BLKIF_OP_???                         */
         uint8_t        nr_segments;  /* number of segments                   */
         blkif_vdev_t   handle;       /* only for read/write requests         */
         uint64_t       __attribute__((__aligned__(8))) id;
-        blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
-        struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+        union {
+                struct blkif_x86_64_request_rw rw;
+                struct blkif_x86_64_request_discard discard;
+        } u;
 };
 struct blkif_x86_64_response {
         uint64_t       __attribute__((__aligned__(8))) id;
@@ -113,6 +139,11 @@ enum blkif_protocol {
         BLKIF_PROTOCOL_X86_64 = 3,
 };
 
+enum blkif_backend_type {
+        BLKIF_BACKEND_PHY  = 1,
+        BLKIF_BACKEND_FILE = 2,
+};
+
 struct xen_vbd {
         /* What the domain refers to this vbd as. */
         blkif_vdev_t            handle;
@@ -138,6 +169,7 @@ struct xen_blkif {
         unsigned int            irq;
         /* Comms information. */
         enum blkif_protocol     blk_protocol;
+        enum blkif_backend_type blk_backend_type;
         union blkif_back_rings  blk_rings;
         struct vm_struct        *blk_ring_area;
         /* The VBD attached to this interface. */
@@ -159,6 +191,7 @@ struct xen_blkif {
         int                     st_wr_req;
         int                     st_oo_req;
         int                     st_f_req;
+        int                     st_ds_req;
         int                     st_rd_sect;
         int                     st_wr_sect;
 
@@ -182,7 +215,7 @@ 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;
 };
@@ -206,12 +239,25 @@ static inline void blkif_get_x86_32_req(struct blkif_request *dst,
         dst->nr_segments = src->nr_segments;
         dst->handle = src->handle;
         dst->id = src->id;
-        dst->u.rw.sector_number = src->sector_number;
-        barrier();
-        if (n > dst->nr_segments)
-                n = dst->nr_segments;
-        for (i = 0; i < n; i++)
-                dst->u.rw.seg[i] = src->seg[i];
+        switch (src->operation) {
+        case BLKIF_OP_READ:
+        case BLKIF_OP_WRITE:
+        case BLKIF_OP_WRITE_BARRIER:
+        case BLKIF_OP_FLUSH_DISKCACHE:
+                dst->u.rw.sector_number = src->u.rw.sector_number;
+                barrier();
+                if (n > dst->nr_segments)
+                        n = dst->nr_segments;
+                for (i = 0; i < n; i++)
+                        dst->u.rw.seg[i] = src->u.rw.seg[i];
+                break;
+        case BLKIF_OP_DISCARD:
+                dst->u.discard.sector_number = src->u.discard.sector_number;
+                dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
+                break;
+        default:
+                break;
+        }
 }
 
 static inline void blkif_get_x86_64_req(struct blkif_request *dst,
@@ -222,12 +268,25 @@ static inline void blkif_get_x86_64_req(struct blkif_request *dst,
         dst->nr_segments = src->nr_segments;
         dst->handle = src->handle;
         dst->id = src->id;
-        dst->u.rw.sector_number = src->sector_number;
-        barrier();
-        if (n > dst->nr_segments)
-                n = dst->nr_segments;
-        for (i = 0; i < n; i++)
-                dst->u.rw.seg[i] = src->seg[i];
+        switch (src->operation) {
+        case BLKIF_OP_READ:
+        case BLKIF_OP_WRITE:
+        case BLKIF_OP_WRITE_BARRIER:
+        case BLKIF_OP_FLUSH_DISKCACHE:
+                dst->u.rw.sector_number = src->u.rw.sector_number;
+                barrier();
+                if (n > dst->nr_segments)
+                        n = dst->nr_segments;
+                for (i = 0; i < n; i++)
+                        dst->u.rw.seg[i] = src->u.rw.seg[i];
+                break;
+        case BLKIF_OP_DISCARD:
+                dst->u.discard.sector_number = src->u.discard.sector_number;
+                dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
+                break;
+        default:
+                break;
+        }
 }
 
 #endif /* __XEN_BLKIF__BACKEND__COMMON_H__ */
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 3f129b45451..2b3aef0332f 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -272,6 +272,7 @@ 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(ds_req,  "%d\n", be->blkif->st_ds_req);
 VBD_SHOW(rd_sect, "%d\n", be->blkif->st_rd_sect);
 VBD_SHOW(wr_sect, "%d\n", be->blkif->st_wr_sect);
 
@@ -280,6 +281,7 @@ static struct attribute *xen_vbdstat_attrs[] = {
         &dev_attr_rd_req.attr,
         &dev_attr_wr_req.attr,
         &dev_attr_f_req.attr,
+        &dev_attr_ds_req.attr,
         &dev_attr_rd_sect.attr,
         &dev_attr_wr_sect.attr,
         NULL
@@ -419,6 +421,60 @@ int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
         return err;
 }
 
+int xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
+{
+        struct xenbus_device *dev = be->dev;
+        struct xen_blkif *blkif = be->blkif;
+        char *type;
+        int err;
+        int state = 0;
+
+        type = xenbus_read(XBT_NIL, dev->nodename, "type", NULL);
+        if (!IS_ERR(type)) {
+                if (strncmp(type, "file", 4) == 0) {
+                        state = 1;
+                        blkif->blk_backend_type = BLKIF_BACKEND_FILE;
+                }
+                if (strncmp(type, "phy", 3) == 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;
+                                blkif->blk_backend_type = BLKIF_BACKEND_PHY;
+                        }
+                }
+        } else {
+                err = PTR_ERR(type);
+                xenbus_dev_fatal(dev, err, "reading type");
+                goto out;
+        }
+
+        err = xenbus_printf(xbt, dev->nodename, "feature-discard",
+                            "%d", state);
+        if (err)
+                xenbus_dev_fatal(dev, err, "writing feature-discard");
+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 +706,8 @@ again:
         if (err)
                 goto abort;
 
+        err = xen_blkbk_discard(xbt, be);
+
         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
                             (unsigned long long)vbd_sz(&be->blkif->vbd));
         if (err) {