nbd/server: Simplify zero and trim

Now that the block layer supports 64-bit operations (see commit
2800637a and friends, new to v6.2), we no longer have to self-fragment
requests larger than 2G, reverting the workaround added in 890cbccb08
("nbd: Fix large trim/zero requests", v5.1.0).

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20211117170230.1128262-3-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

nbd/server.c

@@ -2509,16 +2509,8 @@ static coroutine_fn int nbd_handle_request(NBDClient *client,
         if (request->flags & NBD_CMD_FLAG_FAST_ZERO) {
             flags |= BDRV_REQ_NO_FALLBACK;
         }
-        ret = 0;
-        /* FIXME simplify this when blk_pwrite_zeroes switches to 64-bit */
-        while (ret >= 0 && request->len) {
-            int align = client->check_align ?: 1;
-            int len = MIN(request->len, QEMU_ALIGN_DOWN(BDRV_REQUEST_MAX_BYTES,
-                                                        align));
-            ret = blk_pwrite_zeroes(exp->common.blk, request->from, len, flags);
-            request->len -= len;
-            request->from += len;
-        }
+        ret = blk_pwrite_zeroes(exp->common.blk, request->from, request->len,
+                                flags);
         return nbd_send_generic_reply(client, request->handle, ret,
                                       "writing to file failed", errp);
 
@@ -2532,16 +2524,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client,
                                       "flush failed", errp);
 
     case NBD_CMD_TRIM:
-        ret = 0;
-        /* FIXME simplify this when blk_co_pdiscard switches to 64-bit */
-        while (ret >= 0 && request->len) {
-            int align = client->check_align ?: 1;
-            int len = MIN(request->len, QEMU_ALIGN_DOWN(BDRV_REQUEST_MAX_BYTES,
-                                                        align));
-            ret = blk_co_pdiscard(exp->common.blk, request->from, len);
-            request->len -= len;
-            request->from += len;
-        }
+        ret = blk_co_pdiscard(exp->common.blk, request->from, request->len);
         if (ret >= 0 && request->flags & NBD_CMD_FLAG_FUA) {
             ret = blk_co_flush(exp->common.blk);
         }