From 7a706633e9f77a15d12bcfdef5d80f09892fa70c Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 21 Oct 2011 13:17:14 +0200
Subject: [PATCH] nbd: add support for NBD_CMD_TRIM

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/nbd.c | 25 +++++++++++++++++++++++++
 nbd.c       | 15 +++++++++++++--
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 097b4188e..161b29985 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -435,6 +435,30 @@ static int nbd_co_flush(BlockDriverState *bs)
     return -reply.error;
 }
 
+static int nbd_co_discard(BlockDriverState *bs, int64_t sector_num,
+                          int nb_sectors)
+{
+    BDRVNBDState *s = bs->opaque;
+    struct nbd_request request;
+    struct nbd_reply reply;
+
+    if (!(s->nbdflags & NBD_FLAG_SEND_TRIM)) {
+        return 0;
+    }
+    request.type = NBD_CMD_TRIM;
+    request.from = sector_num * 512;;
+    request.len = nb_sectors * 512;
+
+    nbd_coroutine_start(s, &request);
+    if (nbd_co_send_request(s, &request, NULL, 0) == -1) {
+        reply.error = errno;
+    } else {
+        nbd_co_receive_reply(s, &request, &reply, NULL, 0);
+    }
+    nbd_coroutine_end(s, &request);
+    return -reply.error;
+}
+
 static void nbd_close(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
@@ -459,6 +483,7 @@ static BlockDriver bdrv_nbd = {
     .bdrv_co_writev      = nbd_co_writev,
     .bdrv_close          = nbd_close,
     .bdrv_co_flush_to_os = nbd_co_flush,
+    .bdrv_co_discard     = nbd_co_discard,
     .bdrv_getlength      = nbd_getlength,
     .protocol_name       = "nbd",
 };
diff --git a/nbd.c b/nbd.c
index 4fd0f4ed2..7ab1b1f5c 100644
--- a/nbd.c
+++ b/nbd.c
@@ -203,8 +203,8 @@ int nbd_negotiate(int csock, off_t size, uint32_t flags)
     cpu_to_be64w((uint64_t*)(buf + 8), 0x00420281861253LL);
     cpu_to_be64w((uint64_t*)(buf + 16), size);
     cpu_to_be32w((uint32_t*)(buf + 24),
-                 flags | NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_FLUSH |
-                 NBD_FLAG_SEND_FUA);
+                 flags | NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
+                 NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA);
     memset(buf + 28, 0, 124);
 
     if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
@@ -720,6 +720,17 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset,
             reply.error = -ret;
         }
 
+        if (nbd_send_reply(csock, &reply) == -1)
+            return -1;
+        break;
+    case NBD_CMD_TRIM:
+        TRACE("Request type is TRIM");
+        ret = bdrv_discard(bs, (request.from + dev_offset) / 512,
+                           request.len / 512);
+        if (ret < 0) {
+            LOG("discard failed");
+            reply.error = -ret;
+        }
         if (nbd_send_reply(csock, &reply) == -1)
             return -1;
         break;