nbd: Rely on block layer to break up large requests

Now that the block layer will honor max_transfer, we can simplify
our code to rely on that guarantee.

The readv code can call directly into nbd-client, just as the
writev code has done since commit 52a4650.

Interestingly enough, while qemu-io 'w 0 40m' splits into a 32M
and 8M transaction, 'w -z 0 40m' splits into two 16M and an 8M,
because the block layer caps the bounce buffer for writing zeroes
at 16M.  When we later introduce support for NBD_CMD_WRITE_ZEROES,
we can get a full 32M zero write (or larger, if the client and
server negotiate that write zeroes can use a larger size than
ordinary writes).

Signed-off-by: Eric Blake <[email protected]>
Reviewed-by: Fam Zheng <[email protected]>
Reviewed-by: Stefan Hajnoczi <[email protected]>
Acked-by: Paolo Bonzini <[email protected]>
Message-id: 1468607524[email protected]
Signed-off-by: Stefan Hajnoczi <[email protected]>

diff --git a/block/nbd-client.c b/block/nbd-client.c
index 4cc408d2063f9ace0a5583f24753426da150625c..f1fb58bf269195ccad749d6df34b1d8fb05352a9 100644 (file)
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -217,15 +217,15 @@ static void nbd_coroutine_end(NbdClientSession *s,
     }
 }
 
     }
 }
 

-static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num,
-                          int nb_sectors, QEMUIOVector *qiov,
-                          int offset)
+int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num,
+                        int nb_sectors, QEMUIOVector *qiov)

 {
     NbdClientSession *client = nbd_get_client_session(bs);
     struct nbd_request request = { .type = NBD_CMD_READ };
     struct nbd_reply reply;
     ssize_t ret;
 
 {
     NbdClientSession *client = nbd_get_client_session(bs);
     struct nbd_request request = { .type = NBD_CMD_READ };
     struct nbd_reply reply;
     ssize_t ret;
 

+    assert(nb_sectors <= NBD_MAX_SECTORS);

     request.from = sector_num * 512;
     request.len = nb_sectors * 512;
 
     request.from = sector_num * 512;
     request.len = nb_sectors * 512;
 


@@ -234,16 +234,15 @@ static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num,
     if (ret < 0) {
         reply.error = -ret;
     } else {
     if (ret < 0) {
         reply.error = -ret;
     } else {

-        nbd_co_receive_reply(client, &request, &reply, qiov, offset);
+        nbd_co_receive_reply(client, &request, &reply, qiov, 0);

     }
     nbd_coroutine_end(client, &request);
     return -reply.error;
 
 }
 
     }
     nbd_coroutine_end(client, &request);
     return -reply.error;
 
 }
 

-static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
-                           int nb_sectors, QEMUIOVector *qiov,
-                           int offset, int flags)
+int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
+                         int nb_sectors, QEMUIOVector *qiov, int flags)

 {
     NbdClientSession *client = nbd_get_client_session(bs);
     struct nbd_request request = { .type = NBD_CMD_WRITE };
 {
     NbdClientSession *client = nbd_get_client_session(bs);
     struct nbd_request request = { .type = NBD_CMD_WRITE };


@@ -255,11 +254,12 @@ static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
         request.type |= NBD_CMD_FLAG_FUA;
     }
 
         request.type |= NBD_CMD_FLAG_FUA;
     }
 

+    assert(nb_sectors <= NBD_MAX_SECTORS);

     request.from = sector_num * 512;
     request.len = nb_sectors * 512;
 
     nbd_coroutine_start(client, &request);
     request.from = sector_num * 512;
     request.len = nb_sectors * 512;
 
     nbd_coroutine_start(client, &request);

-    ret = nbd_co_send_request(bs, &request, qiov, offset);
+    ret = nbd_co_send_request(bs, &request, qiov, 0);

     if (ret < 0) {
         reply.error = -ret;
     } else {
     if (ret < 0) {
         reply.error = -ret;
     } else {


@@ -269,41 +269,6 @@ static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
     return -reply.error;
 }
 
     return -reply.error;
 }
 

-int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num,
-                        int nb_sectors, QEMUIOVector *qiov)
-{
-    int offset = 0;
-    int ret;
-    while (nb_sectors > NBD_MAX_SECTORS) {
-        ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
-        if (ret < 0) {
-            return ret;
-        }
-        offset += NBD_MAX_SECTORS * 512;
-        sector_num += NBD_MAX_SECTORS;
-        nb_sectors -= NBD_MAX_SECTORS;
-    }
-    return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset);
-}
-
-int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
-                         int nb_sectors, QEMUIOVector *qiov, int flags)
-{
-    int offset = 0;
-    int ret;
-    while (nb_sectors > NBD_MAX_SECTORS) {
-        ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset,
-                              flags);
-        if (ret < 0) {
-            return ret;
-        }
-        offset += NBD_MAX_SECTORS * 512;
-        sector_num += NBD_MAX_SECTORS;
-        nb_sectors -= NBD_MAX_SECTORS;
-    }
-    return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset, flags);
-}
-

 int nbd_client_co_flush(BlockDriverState *bs)
 {
     NbdClientSession *client = nbd_get_client_session(bs);
 int nbd_client_co_flush(BlockDriverState *bs)
 {
     NbdClientSession *client = nbd_get_client_session(bs);

diff --git a/block/nbd.c b/block/nbd.c
index 08e5b67b2f197193cfb68a8f492c9ebad481d5a3..8a130787c5006551ae0691784d9efa9b1d7c4a78 100644 (file)
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -349,12 +349,6 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
     return ret;
 }
 
     return ret;
 }
 

-static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num,
-                        int nb_sectors, QEMUIOVector *qiov)
-{
-    return nbd_client_co_readv(bs, sector_num, nb_sectors, qiov);
-}
-

 static int nbd_co_flush(BlockDriverState *bs)
 {
     return nbd_client_co_flush(bs);
 static int nbd_co_flush(BlockDriverState *bs)
 {
     return nbd_client_co_flush(bs);


@@ -450,7 +444,7 @@ static BlockDriver bdrv_nbd = {
     .instance_size              = sizeof(BDRVNBDState),
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,
     .instance_size              = sizeof(BDRVNBDState),
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,

-    .bdrv_co_readv              = nbd_co_readv,
+    .bdrv_co_readv              = nbd_client_co_readv,

     .bdrv_co_writev_flags       = nbd_client_co_writev,
     .bdrv_close                 = nbd_close,
     .bdrv_co_flush_to_os        = nbd_co_flush,
     .bdrv_co_writev_flags       = nbd_client_co_writev,
     .bdrv_close                 = nbd_close,
     .bdrv_co_flush_to_os        = nbd_co_flush,


@@ -468,7 +462,7 @@ static BlockDriver bdrv_nbd_tcp = {
     .instance_size              = sizeof(BDRVNBDState),
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,
     .instance_size              = sizeof(BDRVNBDState),
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,

-    .bdrv_co_readv              = nbd_co_readv,
+    .bdrv_co_readv              = nbd_client_co_readv,

     .bdrv_co_writev_flags       = nbd_client_co_writev,
     .bdrv_close                 = nbd_close,
     .bdrv_co_flush_to_os        = nbd_co_flush,
     .bdrv_co_writev_flags       = nbd_client_co_writev,
     .bdrv_close                 = nbd_close,
     .bdrv_co_flush_to_os        = nbd_co_flush,


@@ -486,7 +480,7 @@ static BlockDriver bdrv_nbd_unix = {
     .instance_size              = sizeof(BDRVNBDState),
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,
     .instance_size              = sizeof(BDRVNBDState),
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,

-    .bdrv_co_readv              = nbd_co_readv,
+    .bdrv_co_readv              = nbd_client_co_readv,

     .bdrv_co_writev_flags       = nbd_client_co_writev,
     .bdrv_close                 = nbd_close,
     .bdrv_co_flush_to_os        = nbd_co_flush,
     .bdrv_co_writev_flags       = nbd_client_co_writev,
     .bdrv_close                 = nbd_close,
     .bdrv_co_flush_to_os        = nbd_co_flush,