From f834b08ab5b70b9a39bb0b6c351a65ad46b5879f Mon Sep 17 00:00:00 2001

From: John Snow <jsnow@redhat.com>

Date: Wed, 18 Jul 2018 22:55:06 +0200

Subject: [PATCH 81/89] nbd/server: introduce NBD_CMD_CACHE

RH-Author: John Snow <jsnow@redhat.com>

Message-id: <20180718225511.14878-31-jsnow@redhat.com>

Patchwork-id: 81419

O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH 30/35] nbd/server: introduce NBD_CMD_CACHE

Bugzilla: 1207657

RH-Acked-by: Eric Blake <eblake@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

RH-Acked-by: Fam Zheng <famz@redhat.com>

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Handle nbd CACHE command. Just do read, without sending read data back.

Cache mechanism should be done by exported node driver chain.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Message-Id: <20180413143156.11409-1-vsementsov@virtuozzo.com>

Reviewed-by: Eric Blake <eblake@redhat.com>

[eblake: fix two missing case labels in switch statements]

Signed-off-by: Eric Blake <eblake@redhat.com>

(cherry picked from commit bc37b06a5cde24fb24c2a2cc44dd86756034ba9d)

Signed-off-by: John Snow <jsnow@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 include/block/nbd.h |  3 ++-

 nbd/common.c        |  2 ++

 nbd/server.c        | 11 +++++++----

 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/include/block/nbd.h b/include/block/nbd.h

index 8bb9606..daaeae6 100644

--- a/include/block/nbd.h

+++ b/include/block/nbd.h

@@ -135,6 +135,7 @@ typedef struct NBDExtent {

 #define NBD_FLAG_SEND_TRIM         (1 << 5) /* Send TRIM (discard) */

 #define NBD_FLAG_SEND_WRITE_ZEROES (1 << 6) /* Send WRITE_ZEROES */

 #define NBD_FLAG_SEND_DF           (1 << 7) /* Send DF (Do not Fragment) */

+#define NBD_FLAG_SEND_CACHE        (1 << 8) /* Send CACHE (prefetch) */

 /* New-style handshake (global) flags, sent from server to client, and

    control what will happen during handshake phase. */

@@ -195,7 +196,7 @@ enum {

     NBD_CMD_DISC = 2,

     NBD_CMD_FLUSH = 3,

     NBD_CMD_TRIM = 4,

-    /* 5 reserved for failed experiment NBD_CMD_CACHE */

+    NBD_CMD_CACHE = 5,

     NBD_CMD_WRITE_ZEROES = 6,

     NBD_CMD_BLOCK_STATUS = 7,

 };

diff --git a/nbd/common.c b/nbd/common.c

index 8c95c1d..41f5ed8 100644

--- a/nbd/common.c

+++ b/nbd/common.c

@@ -148,6 +148,8 @@ const char *nbd_cmd_lookup(uint16_t cmd)

         return "flush";

     case NBD_CMD_TRIM:

         return "trim";

+    case NBD_CMD_CACHE:

+        return "cache";

     case NBD_CMD_WRITE_ZEROES:

         return "write zeroes";

     case NBD_CMD_BLOCK_STATUS:

diff --git a/nbd/server.c b/nbd/server.c

index 2c2d62c..2746046 100644

--- a/nbd/server.c

+++ b/nbd/server.c

@@ -1252,7 +1252,7 @@ static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)

     int ret;

     const uint16_t myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |

                               NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA |

-                              NBD_FLAG_SEND_WRITE_ZEROES);

+                              NBD_FLAG_SEND_WRITE_ZEROES | NBD_FLAG_SEND_CACHE);

     bool oldStyle;

     /* Old style negotiation header, no room for options

@@ -2034,7 +2034,9 @@ static int nbd_co_receive_request(NBDRequestData *req, NBDRequest *request,

         return -EIO;

     }

-    if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE) {

+    if (request->type == NBD_CMD_READ || request->type == NBD_CMD_WRITE ||

+        request->type == NBD_CMD_CACHE)

+    {

         if (request->len > NBD_MAX_BUFFER_SIZE) {

             error_setg(errp, "len (%" PRIu32" ) is larger than max len (%u)",

                        request->len, NBD_MAX_BUFFER_SIZE);

@@ -2119,7 +2121,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,

     int ret;

     NBDExport *exp = client->exp;

-    assert(request->type == NBD_CMD_READ);

+    assert(request->type == NBD_CMD_READ || request->type == NBD_CMD_CACHE);

     /* XXX: NBD Protocol only documents use of FUA with WRITE */

     if (request->flags & NBD_CMD_FLAG_FUA) {

@@ -2138,7 +2140,7 @@ static coroutine_fn int nbd_do_cmd_read(NBDClient *client, NBDRequest *request,

     ret = blk_pread(exp->blk, request->from + exp->dev_offset, data,

                     request->len);

-    if (ret < 0) {

+    if (ret < 0 || request->type == NBD_CMD_CACHE) {

         return nbd_send_generic_reply(client, request->handle, ret,

                                       "reading from file failed", errp);

     }

@@ -2171,6 +2173,7 @@ static coroutine_fn int nbd_handle_request(NBDClient *client,

     switch (request->type) {

     case NBD_CMD_READ:

+    case NBD_CMD_CACHE:

         return nbd_do_cmd_read(client, request, data, errp);

     case NBD_CMD_WRITE:

-- 

1.8.3.1