From: Eric Blake <eblake@redhat.com>
Date: Wed, 8 Nov 2017 21:57:00 +0000 (-0600)
Subject: nbd: Fix struct name for structured reads
X-Git-Tag: v2.11.0-rc1~11^2~3
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=efdc0c103d7919e5cabfc0b12a5699c1f8e482db;p=thirdparty%2Fqemu.git

nbd: Fix struct name for structured reads

A closer read of the NBD spec shows that a structured reply chunk
for a hole is not quite identical to the prefix of a data chunk,
because the hole has to also send a 32-bit size field.  Although
we do not yet send holes, we should fix the misleading information
in our header and make it easier for a future patch to support
sparse reads.  Messed up in commit bae245d1.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20171108215703.9295-5-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---

diff --git a/include/block/nbd.h b/include/block/nbd.h
index 92d1723d7cd..113c707a5e9 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -86,15 +86,23 @@ typedef union NBDReply {
     } QEMU_PACKED;
 } NBDReply;
 
-/* Header of NBD_REPLY_TYPE_OFFSET_DATA, complete NBD_REPLY_TYPE_OFFSET_HOLE */
-typedef struct NBDStructuredRead {
-    NBDStructuredReplyChunk h;
+/* Header of chunk for NBD_REPLY_TYPE_OFFSET_DATA */
+typedef struct NBDStructuredReadData {
+    NBDStructuredReplyChunk h; /* h.length >= 9 */
     uint64_t offset;
-} QEMU_PACKED NBDStructuredRead;
+    /* At least one byte of data payload follows, calculated from h.length */
+} QEMU_PACKED NBDStructuredReadData;
+
+/* Complete chunk for NBD_REPLY_TYPE_OFFSET_HOLE */
+typedef struct NBDStructuredReadHole {
+    NBDStructuredReplyChunk h; /* h.length == 12 */
+    uint64_t offset;
+    uint32_t length;
+} QEMU_PACKED NBDStructuredReadHole;
 
 /* Header of all NBD_REPLY_TYPE_ERROR* errors */
 typedef struct NBDStructuredError {
-    NBDStructuredReplyChunk h;
+    NBDStructuredReplyChunk h; /* h.length >= 6 */
     uint32_t error;
     uint16_t message_length;
 } QEMU_PACKED NBDStructuredError;
diff --git a/nbd/server.c b/nbd/server.c
index bcf0cdb47cc..6ebb7d9c2e0 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1280,7 +1280,7 @@ static int coroutine_fn nbd_co_send_structured_read(NBDClient *client,
                                                     size_t size,
                                                     Error **errp)
 {
-    NBDStructuredRead chunk;
+    NBDStructuredReadData chunk;
     struct iovec iov[] = {
         {.iov_base = &chunk, .iov_len = sizeof(chunk)},
         {.iov_base = data, .iov_len = size}