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From 2a68d801c63137c3d1fe9fa96f0193eb2d1576f5 Mon Sep 17 00:00:00 2001
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From: Fam Zheng <famz@redhat.com>
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Date: Thu, 10 Mar 2016 04:00:52 +0100
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Subject: [PATCH 3/5] nbd-server: Coroutine based negotiation
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RH-Author: Fam Zheng <famz@redhat.com>
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Message-id: <1457582453-13835-3-git-send-email-famz@redhat.com>
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Patchwork-id: 69758
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O-Subject: [RHEL-7.3 qemu-kvm PATCH v2 2/3] nbd-server: Coroutine based negotiation
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Bugzilla: 1285453
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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Create a coroutine in nbd_client_new, so that nbd_send_negotiate doesn't
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need qemu_set_block().
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Handlers need to be set temporarily for csock fd in case the coroutine
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yields during I/O.
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With this, if the other end disappears in the middle of the negotiation,
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we don't block the whole event loop.
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To make the code clearer, unify all function names that belong to
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negotiate, so they are less likely to be misused. This is important
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because we rely on negotiation staying in main loop, as commented in
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nbd_negotiate_read/write().
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Signed-off-by: Fam Zheng <famz@redhat.com>
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Message-Id: <1452760863-25350-4-git-send-email-famz@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 1a6245a5b0b4e8d822c739b403fc67c8a7bc8d12)
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Signed-off-by: Fam Zheng <famz@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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Conflicts:
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	nbd.c
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Downstream doesn't have new style protocol, and the code is not split.
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The patch is redone.
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---
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 nbd.c | 106 +++++++++++++++++++++++++++++++++++++++++++++++++++---------------
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 1 file changed, 82 insertions(+), 24 deletions(-)
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diff --git a/nbd.c b/nbd.c
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index ba97270..97aeecb 100644
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--- a/nbd.c
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+++ b/nbd.c
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@@ -167,6 +167,41 @@ ssize_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read)
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     return offset;
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 }
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+static void nbd_negotiate_continue(void *opaque)
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+{
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+    qemu_coroutine_enter(opaque, NULL);
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+}
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+
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+static ssize_t read_sync(int fd, void *buffer, size_t size);
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+static ssize_t write_sync(int fd, void *buffer, size_t size);
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+
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+static ssize_t nbd_negotiate_read(int fd, void *buffer, size_t size)
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+{
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+    ssize_t ret;
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+
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+    assert(qemu_in_coroutine());
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+    /* Negotiation are always in main loop. */
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+    qemu_set_fd_handler(fd, nbd_negotiate_continue, NULL,
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+                        qemu_coroutine_self());
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+    ret = read_sync(fd, buffer, size);
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+    qemu_set_fd_handler(fd, NULL, NULL, NULL);
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+    return ret;
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+
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+}
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+
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+static ssize_t nbd_negotiate_write(int fd, void *buffer, size_t size)
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+{
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+    ssize_t ret;
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+
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+    assert(qemu_in_coroutine());
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+    /* Negotiation are always in main loop. */
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+    qemu_set_fd_handler(fd, NULL, nbd_negotiate_continue,
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+                        qemu_coroutine_self());
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+    ret = write_sync(fd, buffer, size);
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+    qemu_set_fd_handler(fd, NULL, NULL, NULL);
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+    return ret;
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+}
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+
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 static ssize_t read_sync(int fd, void *buffer, size_t size)
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 {
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     /* Sockets are kept in blocking mode in the negotiation phase.  After
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@@ -280,7 +315,7 @@ int unix_socket_outgoing(const char *path)
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 */
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-static int nbd_receive_options(NBDClient *client)
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+static coroutine_fn int nbd_negotiate_receive_options(NBDClient *client)
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 {
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     int csock = client->sock;
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     char name[256];
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@@ -297,7 +332,7 @@ static int nbd_receive_options(NBDClient *client)
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      */
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     rc = -EINVAL;
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-    if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
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+    if (nbd_negotiate_read(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
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         LOG("read failed");
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         goto fail;
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     }
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@@ -307,7 +342,7 @@ static int nbd_receive_options(NBDClient *client)
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         goto fail;
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     }
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-    if (read_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
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+    if (nbd_negotiate_read(csock, &magic, sizeof(magic)) != sizeof(magic)) {
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         LOG("read failed");
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         goto fail;
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     }
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@@ -317,7 +352,7 @@ static int nbd_receive_options(NBDClient *client)
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         goto fail;
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     }
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-    if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
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+    if (nbd_negotiate_read(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
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         LOG("read failed");
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         goto fail;
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     }
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@@ -327,7 +362,7 @@ static int nbd_receive_options(NBDClient *client)
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         goto fail;
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     }
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-    if (read_sync(csock, &length, sizeof(length)) != sizeof(length)) {
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+    if (nbd_negotiate_read(csock, &length, sizeof(length)) != sizeof(length)) {
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         LOG("read failed");
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         goto fail;
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     }
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@@ -337,7 +372,7 @@ static int nbd_receive_options(NBDClient *client)
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         LOG("Bad length received");
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         goto fail;
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     }
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-    if (read_sync(csock, name, length) != length) {
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+    if (nbd_negotiate_read(csock, name, length) != length) {
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         LOG("read failed");
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         goto fail;
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     }
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@@ -358,8 +393,14 @@ fail:
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     return rc;
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 }
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-static int nbd_send_negotiate(NBDClient *client)
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+typedef struct {
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+    NBDClient *client;
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+    Coroutine *co;
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+} NBDClientNewData;
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+
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+static coroutine_fn int nbd_negotiate(NBDClientNewData *data)
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 {
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+    NBDClient *client = data->client;
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     int csock = client->sock;
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     char buf[8 + 8 + 8 + 128];
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     int rc;
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@@ -385,7 +426,6 @@ static int nbd_send_negotiate(NBDClient *client)
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         [28 .. 151]   reserved     (0)
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      */
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-    qemu_set_block(csock);
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     rc = -EINVAL;
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     TRACE("Beginning negotiation.");
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@@ -401,16 +441,16 @@ static int nbd_send_negotiate(NBDClient *client)
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     }
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     if (client->exp) {
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-        if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
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+        if (nbd_negotiate_write(csock, buf, sizeof(buf)) != sizeof(buf)) {
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             LOG("write failed");
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             goto fail;
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         }
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     } else {
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-        if (write_sync(csock, buf, 18) != 18) {
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+        if (nbd_negotiate_write(csock, buf, 18) != 18) {
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             LOG("write failed");
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             goto fail;
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         }
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-        rc = nbd_receive_options(client);
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+        rc = nbd_negotiate_receive_options(client);
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         if (rc < 0) {
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             LOG("option negotiation failed");
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             goto fail;
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@@ -419,7 +459,8 @@ static int nbd_send_negotiate(NBDClient *client)
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         assert ((client->exp->nbdflags & ~65535) == 0);
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         cpu_to_be64w((uint64_t*)(buf + 18), client->exp->size);
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         cpu_to_be16w((uint16_t*)(buf + 26), client->exp->nbdflags | myflags);
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-        if (write_sync(csock, buf + 18, sizeof(buf) - 18) != sizeof(buf) - 18) {
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+        if (nbd_negotiate_write(csock, buf + 18,
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+                                sizeof(buf) - 18) != sizeof(buf) - 18) {
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             LOG("write failed");
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             goto fail;
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         }
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@@ -428,7 +469,6 @@ static int nbd_send_negotiate(NBDClient *client)
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     TRACE("Negotiation succeeded.");
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     rc = 0;
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 fail:
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-    qemu_set_nonblock(csock);
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     return rc;
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 }
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@@ -1232,24 +1272,42 @@ static void nbd_restart_write(void *opaque)
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     qemu_coroutine_enter(client->send_coroutine, NULL);
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 }
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+static coroutine_fn void nbd_co_client_start(void *opaque)
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+{
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+    NBDClientNewData *data = opaque;
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+    NBDClient *client = data->client;
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+    NBDExport *exp = client->exp;
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+
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+    if (exp) {
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+        nbd_export_get(exp);
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+    }
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+    if (nbd_negotiate(data)) {
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+        shutdown(client->sock, 2);
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+        client->close(client);
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+        goto out;
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+    }
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+    qemu_co_mutex_init(&client->send_lock);
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+    qemu_set_fd_handler2(client->sock, nbd_can_read, nbd_read, NULL, client);
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+
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+    if (exp) {
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+        QTAILQ_INSERT_TAIL(&exp->clients, client, next);
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+    }
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+out:
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+    g_free(data);
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+}
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+
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 void nbd_client_new(NBDExport *exp, int csock, void (*close_fn)(NBDClient *))
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 {
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     NBDClient *client;
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+    NBDClientNewData *data = g_new(NBDClientNewData, 1);
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+
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     client = g_malloc0(sizeof(NBDClient));
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     client->refcount = 1;
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     client->exp = exp;
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     client->sock = csock;
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-    if (nbd_send_negotiate(client) < 0) {
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-        shutdown(client->sock, 2);
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-        close_fn(client);
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-        return;
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-    }
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     client->close = close_fn;
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-    qemu_co_mutex_init(&client->send_lock);
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-    qemu_set_fd_handler2(csock, nbd_can_read, nbd_read, NULL, client);
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-    if (exp) {
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-        QTAILQ_INSERT_TAIL(&exp->clients, client, next);
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-        nbd_export_get(exp);
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-    }
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+    data->client = client;
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+    data->co = qemu_coroutine_create(nbd_co_client_start);
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+    qemu_coroutine_enter(data->co, data);
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 }
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-- 
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1.8.3.1
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