[PATCH 3/5] block/nbd.c: Add yank feature

[Lukas Straub]

Add yank option, pass it to the socket-channel and register a yank
function which sets s->state = NBD_CLIENT_QUIT. This is the same
behaviour as if an error occured.

Signed-off-by: Lukas Straub <address@hidden>
---
 Makefile.objs        |  1 +
 block/nbd.c          | 68 +++++++++++++++++++++++++++++++++-----------
 qapi/block-core.json |  5 +++-
 3 files changed, 56 insertions(+), 18 deletions(-)

diff --git a/Makefile.objs b/Makefile.objs
index 889115775c..4b213b3e78 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -18,6 +18,7 @@ block-obj-y += block.o blockjob.o job.o
 block-obj-y += block/ scsi/
 block-obj-y += qemu-io-cmds.o
 block-obj-$(CONFIG_REPLICATION) += replication.o
+block-obj-y += yank.o
 
 block-obj-m = block/
 
diff --git a/block/nbd.c b/block/nbd.c
index 2160859f64..3c0fd3abb8 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -35,6 +35,7 @@
 #include "qemu/option.h"
 #include "qemu/cutils.h"
 #include "qemu/main-loop.h"
+#include "qemu/atomic.h"
 
 #include "qapi/qapi-visit-sockets.h"
 #include "qapi/qmp/qstring.h"
@@ -43,6 +44,8 @@
 #include "block/nbd.h"
 #include "block/block_int.h"
 
+#include "yank.h"
+
 #define EN_OPTSTR ":exportname="
 #define MAX_NBD_REQUESTS    16
 
@@ -91,6 +94,7 @@ typedef struct BDRVNBDState {
     QCryptoTLSCreds *tlscreds;
     const char *hostname;
     char *x_dirty_bitmap;
+    bool yank;
 } BDRVNBDState;
 
 static int nbd_client_connect(BlockDriverState *bs, Error **errp);
@@ -111,12 +115,12 @@ static void nbd_clear_bdrvstate(BDRVNBDState *s)
 static void nbd_channel_error(BDRVNBDState *s, int ret)
 {
     if (ret == -EIO) {
-        if (s->state == NBD_CLIENT_CONNECTED) {
+        if (atomic_read(&s->state) == NBD_CLIENT_CONNECTED) {
             s->state = s->reconnect_delay ? NBD_CLIENT_CONNECTING_WAIT :
                                             NBD_CLIENT_CONNECTING_NOWAIT;
         }
     } else {
-        if (s->state == NBD_CLIENT_CONNECTED) {
+        if (atomic_read(&s->state) == NBD_CLIENT_CONNECTED) {
             qio_channel_shutdown(s->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
         }
         s->state = NBD_CLIENT_QUIT;
@@ -167,7 +171,7 @@ static void nbd_client_attach_aio_context(BlockDriverState 
*bs,
      * s->connection_co is either yielded from nbd_receive_reply or from
      * nbd_co_reconnect_loop()
      */
-    if (s->state == NBD_CLIENT_CONNECTED) {
+    if (atomic_read(&s->state) == NBD_CLIENT_CONNECTED) {
         qio_channel_attach_aio_context(QIO_CHANNEL(s->ioc), new_context);
     }
 
@@ -206,7 +210,7 @@ static void nbd_teardown_connection(BlockDriverState *bs)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
 
-    if (s->state == NBD_CLIENT_CONNECTED) {
+    if (atomic_read(&s->state) == NBD_CLIENT_CONNECTED) {
         /* finish any pending coroutines */
         assert(s->ioc);
         qio_channel_shutdown(s->ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
@@ -230,13 +234,14 @@ static void nbd_teardown_connection(BlockDriverState *bs)
 
 static bool nbd_client_connecting(BDRVNBDState *s)
 {
-    return s->state == NBD_CLIENT_CONNECTING_WAIT ||
-        s->state == NBD_CLIENT_CONNECTING_NOWAIT;
+    NBDClientState state = atomic_read(&s->state);
+    return state == NBD_CLIENT_CONNECTING_WAIT ||
+        state == NBD_CLIENT_CONNECTING_NOWAIT;
 }
 
 static bool nbd_client_connecting_wait(BDRVNBDState *s)
 {
-    return s->state == NBD_CLIENT_CONNECTING_WAIT;
+    return atomic_read(&s->state) == NBD_CLIENT_CONNECTING_WAIT;
 }
 
 static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s)
@@ -305,7 +310,7 @@ static coroutine_fn void nbd_co_reconnect_loop(BDRVNBDState 
*s)
     nbd_reconnect_attempt(s);
 
     while (nbd_client_connecting(s)) {
-        if (s->state == NBD_CLIENT_CONNECTING_WAIT &&
+        if (atomic_read(&s->state) == NBD_CLIENT_CONNECTING_WAIT &&
             qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - start_time_ns > delay_ns)
         {
             s->state = NBD_CLIENT_CONNECTING_NOWAIT;
@@ -341,7 +346,7 @@ static coroutine_fn void nbd_connection_entry(void *opaque)
     int ret = 0;
     Error *local_err = NULL;
 
-    while (s->state != NBD_CLIENT_QUIT) {
+    while (atomic_read(&s->state) != NBD_CLIENT_QUIT) {
         /*
          * The NBD client can only really be considered idle when it has
          * yielded from qio_channel_readv_all_eof(), waiting for data. This is
@@ -356,7 +361,7 @@ static coroutine_fn void nbd_connection_entry(void *opaque)
             nbd_co_reconnect_loop(s);
         }
 
-        if (s->state != NBD_CLIENT_CONNECTED) {
+        if (atomic_read(&s->state) != NBD_CLIENT_CONNECTED) {
             continue;
         }
 
@@ -435,7 +440,7 @@ static int nbd_co_send_request(BlockDriverState *bs,
         qemu_co_queue_wait(&s->free_sema, &s->send_mutex);
     }
 
-    if (s->state != NBD_CLIENT_CONNECTED) {
+    if (atomic_read(&s->state) != NBD_CLIENT_CONNECTED) {
         rc = -EIO;
         goto err;
     }
@@ -462,7 +467,7 @@ static int nbd_co_send_request(BlockDriverState *bs,
     if (qiov) {
         qio_channel_set_cork(s->ioc, true);
         rc = nbd_send_request(s->ioc, request);
-        if (rc >= 0 && s->state == NBD_CLIENT_CONNECTED) {
+        if (rc >= 0 && atomic_read(&s->state) == NBD_CLIENT_CONNECTED) {
             if (qio_channel_writev_all(s->ioc, qiov->iov, qiov->niov,
                                        NULL) < 0) {
                 rc = -EIO;
@@ -777,7 +782,7 @@ static coroutine_fn int nbd_co_do_receive_one_chunk(
     s->requests[i].receiving = true;
     qemu_coroutine_yield();
     s->requests[i].receiving = false;
-    if (s->state != NBD_CLIENT_CONNECTED) {
+    if (atomic_read(&s->state) != NBD_CLIENT_CONNECTED) {
         error_setg(errp, "Connection closed");
         return -EIO;
     }
@@ -936,7 +941,7 @@ static bool nbd_reply_chunk_iter_receive(BDRVNBDState *s,
     NBDReply local_reply;
     NBDStructuredReplyChunk *chunk;
     Error *local_err = NULL;
-    if (s->state != NBD_CLIENT_CONNECTED) {
+    if (atomic_read(&s->state) != NBD_CLIENT_CONNECTED) {
         error_setg(&local_err, "Connection closed");
         nbd_iter_channel_error(iter, -EIO, &local_err);
         goto break_loop;
@@ -961,7 +966,8 @@ static bool nbd_reply_chunk_iter_receive(BDRVNBDState *s,
     }
 
     /* Do not execute the body of NBD_FOREACH_REPLY_CHUNK for simple reply. */
-    if (nbd_reply_is_simple(reply) || s->state != NBD_CLIENT_CONNECTED) {
+    if (nbd_reply_is_simple(reply) ||
+        atomic_read(&s->state) != NBD_CLIENT_CONNECTED) {
         goto break_loop;
     }
 
@@ -1395,6 +1401,14 @@ static int nbd_client_reopen_prepare(BDRVReopenState 
*state,
     return 0;
 }
 
+static void nbd_yank(void *opaque)
+{
+    BlockDriverState *bs = opaque;
+    BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
+
+    atomic_set(&s->state, NBD_CLIENT_QUIT);
+}
+
 static void nbd_client_close(BlockDriverState *bs)
 {
     BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
@@ -1407,14 +1421,17 @@ static void nbd_client_close(BlockDriverState *bs)
     nbd_teardown_connection(bs);
 }
 
-static QIOChannelSocket *nbd_establish_connection(SocketAddress *saddr,
+static QIOChannelSocket *nbd_establish_connection(BlockDriverState *bs,
+                                                  SocketAddress *saddr,
                                                   Error **errp)
 {
+    BDRVNBDState *s = (BDRVNBDState *)bs->opaque;
     QIOChannelSocket *sioc;
     Error *local_err = NULL;
 
     sioc = qio_channel_socket_new();
     qio_channel_set_name(QIO_CHANNEL(sioc), "nbd-client");
+    qio_channel_set_yank(QIO_CHANNEL(sioc), s->yank);
 
     qio_channel_socket_connect_sync(sioc, saddr, &local_err);
     if (local_err) {
@@ -1438,7 +1455,7 @@ static int nbd_client_connect(BlockDriverState *bs, Error 
**errp)
      * establish TCP connection, return error if it fails
      * TODO: Configurable retry-until-timeout behaviour.
      */
-    QIOChannelSocket *sioc = nbd_establish_connection(s->saddr, errp);
+    QIOChannelSocket *sioc = nbd_establish_connection(bs, s->saddr, errp);
 
     if (!sioc) {
         return -ECONNREFUSED;
@@ -1829,6 +1846,12 @@ static QemuOptsList nbd_runtime_opts = {
                     "future requests before a successful reconnect will "
                     "immediately fail. Default 0",
         },
+        {
+            .name = "yank",
+            .type = QEMU_OPT_BOOL,
+            .help = "Forcibly close the connection and don't attempt to "
+                    "reconnect when the 'yank' qmp command is executed.",
+        },
         { /* end of list */ }
     },
 };
@@ -1888,6 +1911,8 @@ static int nbd_process_options(BlockDriverState *bs, 
QDict *options,
 
     s->reconnect_delay = qemu_opt_get_number(opts, "reconnect-delay", 0);
 
+    s->yank = qemu_opt_get_bool(opts, "yank", false);
+
     ret = 0;
 
  error:
@@ -1921,6 +1946,10 @@ static int nbd_open(BlockDriverState *bs, QDict 
*options, int flags,
     /* successfully connected */
     s->state = NBD_CLIENT_CONNECTED;
 
+    if (s->yank) {
+        yank_register_function(nbd_yank, bs);
+    }
+
     s->connection_co = qemu_coroutine_create(nbd_connection_entry, s);
     bdrv_inc_in_flight(bs);
     aio_co_schedule(bdrv_get_aio_context(bs), s->connection_co);
@@ -1972,6 +2001,11 @@ static void nbd_close(BlockDriverState *bs)
     BDRVNBDState *s = bs->opaque;
 
     nbd_client_close(bs);
+
+    if (s->yank) {
+        yank_unregister_function(nbd_yank, bs);
+    }
+
     nbd_clear_bdrvstate(s);
 }
 
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 943df1926a..1c1578160e 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -3862,6 +3862,8 @@
 #                   reconnect. After that time, any delayed requests and all
 #                   future requests before a successful reconnect will
 #                   immediately fail. Default 0 (Since 4.2)
+# @yank: Forcibly close the connection and don't attempt to reconnect when
+#        the 'yank' qmp command is executed. (Since: 5.1)
 #
 # Since: 2.9
 ##
@@ -3870,7 +3872,8 @@
             '*export': 'str',
             '*tls-creds': 'str',
             '*x-dirty-bitmap': 'str',
-            '*reconnect-delay': 'uint32' } }
+            '*reconnect-delay': 'uint32',
+           'yank': 'bool' } }
 
 ##
 # @BlockdevOptionsRaw:
-- 
2.20.1

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