nbd: Convert to byte-based interface

The NBD protocol doesn't have any notion of sectors, so it is
a fairly easy conversion to use byte-based read and write.

Signed-off-by: Eric Blake <eblake@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1468624988-423-19-git-send-email-eblake@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/nbd-client.c

@@ -218,17 +218,20 @@ static void nbd_coroutine_end(NbdClientSession *s,
     }
 }
 
-int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num,
-                        int nb_sectors, QEMUIOVector *qiov)
+int nbd_client_co_preadv(BlockDriverState *bs, uint64_t offset,
+                         uint64_t bytes, QEMUIOVector *qiov, int flags)
 {
     NbdClientSession *client = nbd_get_client_session(bs);
-    struct nbd_request request = { .type = NBD_CMD_READ };
+    struct nbd_request request = {
+        .type = NBD_CMD_READ,
+        .from = offset,
+        .len = bytes,
+    };
     struct nbd_reply reply;
     ssize_t ret;
 
-    assert(nb_sectors <= NBD_MAX_SECTORS);
-    request.from = sector_num * 512;
-    request.len = nb_sectors * 512;
+    assert(bytes <= NBD_MAX_BUFFER_SIZE);
+    assert(!flags);
 
     nbd_coroutine_start(client, &request);
     ret = nbd_co_send_request(bs, &request, NULL);
@@ -239,14 +242,17 @@ int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num,
     }
     nbd_coroutine_end(client, &request);
     return -reply.error;
-
 }
 
-int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
-                         int nb_sectors, QEMUIOVector *qiov, int flags)
+int nbd_client_co_pwritev(BlockDriverState *bs, uint64_t offset,
+                          uint64_t bytes, QEMUIOVector *qiov, int flags)
 {
     NbdClientSession *client = nbd_get_client_session(bs);
-    struct nbd_request request = { .type = NBD_CMD_WRITE };
+    struct nbd_request request = {
+        .type = NBD_CMD_WRITE,
+        .from = offset,
+        .len = bytes,
+    };
     struct nbd_reply reply;
     ssize_t ret;
 
@@ -255,9 +261,7 @@ int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
         request.type |= NBD_CMD_FLAG_FUA;
     }
 
-    assert(nb_sectors <= NBD_MAX_SECTORS);
-    request.from = sector_num * 512;
-    request.len = nb_sectors * 512;
+    assert(bytes <= NBD_MAX_BUFFER_SIZE);
 
     nbd_coroutine_start(client, &request);
     ret = nbd_co_send_request(bs, &request, qiov);

block/nbd-client.h

@@ -46,10 +46,10 @@ void nbd_client_close(BlockDriverState *bs);
 
 int nbd_client_co_pdiscard(BlockDriverState *bs, int64_t offset, int count);
 int nbd_client_co_flush(BlockDriverState *bs);
-int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
-                         int nb_sectors, QEMUIOVector *qiov, int flags);
-int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num,
-                        int nb_sectors, QEMUIOVector *qiov);
+int nbd_client_co_pwritev(BlockDriverState *bs, uint64_t offset,
+                          uint64_t bytes, QEMUIOVector *qiov, int flags);
+int nbd_client_co_preadv(BlockDriverState *bs, uint64_t offset,
+                         uint64_t bytes, QEMUIOVector *qiov, int flags);
 
 void nbd_client_detach_aio_context(BlockDriverState *bs);
 void nbd_client_attach_aio_context(BlockDriverState *bs,

block/nbd.c

@@ -438,8 +438,8 @@ static BlockDriver bdrv_nbd = {
     .instance_size              = sizeof(BDRVNBDState),
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,
-    .bdrv_co_readv              = nbd_client_co_readv,
-    .bdrv_co_writev_flags       = nbd_client_co_writev,
+    .bdrv_co_preadv             = nbd_client_co_preadv,
+    .bdrv_co_pwritev            = nbd_client_co_pwritev,
     .bdrv_close                 = nbd_close,
     .bdrv_co_flush_to_os        = nbd_co_flush,
     .bdrv_co_pdiscard           = nbd_client_co_pdiscard,
@@ -456,8 +456,8 @@ static BlockDriver bdrv_nbd_tcp = {
     .instance_size              = sizeof(BDRVNBDState),
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,
-    .bdrv_co_readv              = nbd_client_co_readv,
-    .bdrv_co_writev_flags       = nbd_client_co_writev,
+    .bdrv_co_preadv             = nbd_client_co_preadv,
+    .bdrv_co_pwritev            = nbd_client_co_pwritev,
     .bdrv_close                 = nbd_close,
     .bdrv_co_flush_to_os        = nbd_co_flush,
     .bdrv_co_pdiscard           = nbd_client_co_pdiscard,
@@ -474,8 +474,8 @@ static BlockDriver bdrv_nbd_unix = {
     .instance_size              = sizeof(BDRVNBDState),
     .bdrv_parse_filename        = nbd_parse_filename,
     .bdrv_file_open             = nbd_open,
-    .bdrv_co_readv              = nbd_client_co_readv,
-    .bdrv_co_writev_flags       = nbd_client_co_writev,
+    .bdrv_co_preadv             = nbd_client_co_preadv,
+    .bdrv_co_pwritev            = nbd_client_co_pwritev,
     .bdrv_close                 = nbd_close,
     .bdrv_co_flush_to_os        = nbd_co_flush,
     .bdrv_co_pdiscard           = nbd_client_co_pdiscard,

include/block/nbd.h

@@ -77,7 +77,6 @@ enum {
 
 /* Maximum size of a single READ/WRITE data buffer */
 #define NBD_MAX_BUFFER_SIZE (32 * 1024 * 1024)
-#define NBD_MAX_SECTORS (NBD_MAX_BUFFER_SIZE / BDRV_SECTOR_SIZE)
 
 /* Maximum size of an export name. The NBD spec requires 256 and
  * suggests that servers support up to 4096, but we stick to only the