[Qemu-devel] [PATCH 06/12] nbd: support NBD_CMD_TRIM in the server

[Paolo Bonzini <pbonzini@redhat.com>]

Map it to bdrv_discard.  The server can now expose NBD_FLAG_SEND_TRIM.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/nbd.c |   31 +++++++++++++++++++++++++++++++
 nbd.c       |    9 ++++++++-
 2 files changed, 39 insertions(+), 1 deletions(-)

diff --git a/block/nbd.c b/block/nbd.c
index 5a7812c..964caa8 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -275,6 +275,36 @@ static int nbd_flush(BlockDriverState *bs)
     return 0;
 }
 
+static int nbd_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.handle = (uint64_t)(intptr_t)bs;
+    request.from = sector_num * 512;;
+    request.len = nb_sectors * 512;
+
+    if (nbd_send_request(s->sock, &request) == -1)
+        return -errno;
+
+    if (nbd_receive_reply(s->sock, &reply) == -1)
+        return -errno;
+
+    if (reply.error !=0)
+        return -reply.error;
+
+    if (reply.handle != request.handle)
+        return -EIO;
+
+    return 0;
+}
+
 static void nbd_close(BlockDriverState *bs)
 {
     BDRVNBDState *s = bs->opaque;
@@ -299,6 +329,7 @@ static BlockDriver bdrv_nbd = {
     .bdrv_write		= nbd_write,
     .bdrv_close		= nbd_close,
     .bdrv_flush		= nbd_flush,
+    .bdrv_discard	= nbd_discard,
     .bdrv_getlength	= nbd_getlength,
     .protocol_name	= "nbd",
 };
diff --git a/nbd.c b/nbd.c
index b65fb4a..f089904 100644
--- a/nbd.c
+++ b/nbd.c
@@ -194,7 +194,7 @@ 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 |
+                 flags | NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
                  NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA);
     memset(buf + 28, 0, 124);
 
@@ -703,6 +703,13 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset,
         if (nbd_send_reply(csock, &reply) == -1)
             return -1;
         break;
+    case NBD_CMD_TRIM:
+        TRACE("Request type is TRIM");
+        bdrv_discard(bs, (request.from + dev_offset) / 512,
+                     request.len / 512);
+        if (nbd_send_reply(csock, &reply) == -1)
+            return -1;
+        break;
     default:
         LOG("invalid request type (%u) received", request.type);
         errno = EINVAL;
-- 
1.7.6