[libvirt RFCv8 01/27] multifd-helper: new helper for parallel save/restore

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For the save direction, this helper listens on a unix socket
which QEMU connects to for multifd migration to files.

For the restore direction, this helper connects to a unix socket
QEMU listens at for multifd migration from files.

The file descriptors are passed as command line parameters.

Signed-off-by: Claudio Fontana <cfontana@xxxxxxx>
---
 po/POTFILES.in            |   1 +
 src/libvirt_private.syms  |   1 +
 src/util/meson.build      |  16 +++
 src/util/multifd-helper.c | 249 ++++++++++++++++++++++++++++++++++++++
 src/util/virthread.c      |   5 +
 src/util/virthread.h      |   1 +
 6 files changed, 273 insertions(+)
 create mode 100644 src/util/multifd-helper.c

diff --git a/po/POTFILES.in b/po/POTFILES.in
index 0d9adb0758..4efb330262 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -241,6 +241,7 @@
 @SRCDIR@src/storage_file/storage_source_backingstore.c
 @SRCDIR@src/test/test_driver.c
 @SRCDIR@src/util/iohelper.c
+@SRCDIR@src/util/multifd-helper.c
 @SRCDIR@src/util/viralloc.c
 @SRCDIR@src/util/virarptable.c
 @SRCDIR@src/util/viraudit.c
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 97bfca906b..5f2bee985e 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3427,6 +3427,7 @@ virThreadCreateFull;
 virThreadID;
 virThreadIsSelf;
 virThreadJoin;
+virThreadJoinRet;
 virThreadMaxName;
 virThreadSelf;
 virThreadSelfID;
diff --git a/src/util/meson.build b/src/util/meson.build
index 17755373c8..337e454137 100644
--- a/src/util/meson.build
+++ b/src/util/meson.build
@@ -178,6 +178,11 @@ io_helper_sources = [
   'virfile.c',
 ]
 
+multifd_helper_sources = [
+  'multifd-helper.c',
+  'virfile.c',
+]
+
 virt_util_lib = static_library(
   'virt_util',
   [
@@ -219,6 +224,17 @@ if conf.has('WITH_LIBVIRTD')
       libutil_dep,
     ],
   }
+  virt_helpers += {
+    'name': 'libvirt_multifd_helper',
+    'sources': [
+      files(multifd_helper_sources),
+      dtrace_gen_headers,
+    ],
+    'deps': [
+      acl_dep,
+      libutil_dep,
+    ],
+  }
 endif
 
 util_inc_dir = include_directories('.')
diff --git a/src/util/multifd-helper.c b/src/util/multifd-helper.c
new file mode 100644
index 0000000000..59657578e2
--- /dev/null
+++ b/src/util/multifd-helper.c
@@ -0,0 +1,249 @@
+/*
+ * multifd-helper.c: listens on Unix socket to perform I/O to multiple files
+ *
+ * Copyright (C) 2022 SUSE LLC
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * This has been written to support QEMU multifd migration to file,
+ * allowing better use of cpu resources to speed up the save/restore.
+ */
+
+#include <config.h>
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include "virthread.h"
+#include "virfile.h"
+#include "virerror.h"
+#include "virstring.h"
+#include "virgettext.h"
+
+#define VIR_FROM_THIS VIR_FROM_STORAGE
+
+typedef struct _multiFdConnData multiFdConnData;
+struct _multiFdConnData {
+    int clientfd;
+    int filefd;
+    int oflags;
+    const char *path;
+    virThread tid;
+
+    off_t total;
+};
+
+typedef struct _multiFdThreadArgs multiFdThreadArgs;
+struct _multiFdThreadArgs {
+    int nchannels;
+    multiFdConnData *conn;     /* contains main fd + nchannels */
+    const char *sun_path;      /* unix socket name to use for the server */
+    struct sockaddr_un serv_addr;
+
+    off_t total;
+};
+
+static void clientThreadFunc(void *a)
+{
+    multiFdConnData *c = a;
+    c->total = virFileDiskCopy(c->filefd, c->path, c->clientfd, "socket");
+}
+
+static off_t waitClientThreads(multiFdConnData *conn, int n)
+{
+    int idx;
+    off_t total = 0;
+    for (idx = 0; idx < n; idx++) {
+        multiFdConnData *c = &conn[idx];
+        if (virThreadJoinRet(&c->tid) < 0) {
+            total = -1;
+        } else if (total >= 0) {
+            total += c->total;
+        }
+        if (VIR_CLOSE(c->clientfd) < 0) {
+            total = -1;
+        }
+    }
+    return total;
+}
+
+static void loadThreadFunc(void *a)
+{
+    multiFdThreadArgs *args = a;
+    int idx;
+    args->total = -1;
+
+    for (idx = 0; idx < args->nchannels + 1; idx++) {
+        /* Perform outgoing connections */
+        multiFdConnData *c = &args->conn[idx];
+        c->clientfd = socket(AF_UNIX, SOCK_STREAM, 0);
+        if (c->clientfd < 0) {
+            virReportSystemError(errno, "%s", _("loadThread: socket() failed"));
+            goto cleanup;
+        }
+        if (connect(c->clientfd, (const struct sockaddr *)&args->serv_addr,
+                    sizeof(struct sockaddr_un)) < 0) {
+            virReportSystemError(errno, "%s", _("loadThread: connect() failed"));
+            goto cleanup;
+        }
+        if (virThreadCreate(&c->tid, true, &clientThreadFunc, c) < 0) {
+            virReportSystemError(errno, "%s", _("loadThread: client thread creation failed"));
+            goto cleanup;
+        }
+    }
+    args->total = waitClientThreads(args->conn, args->nchannels + 1);
+
+ cleanup:
+    for (idx = 0; idx < args->nchannels + 1; idx++) {
+        multiFdConnData *c = &args->conn[idx];
+        VIR_FORCE_CLOSE(c->clientfd);
+    }
+}
+
+static void saveThreadFunc(void *a)
+{
+    multiFdThreadArgs *args = a;
+    int idx;
+    const char buf[1] = {'R'};
+    int sockfd;
+
+    if ((sockfd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) {
+        virReportSystemError(errno, "%s", _("saveThread: socket() failed"));
+        return;
+    }
+    unlink(args->sun_path);
+    if (bind(sockfd, (struct sockaddr *)&args->serv_addr, sizeof(args->serv_addr)) < 0) {
+        virReportSystemError(errno, "%s", _("saveThread: bind() failed"));
+        goto cleanup;
+    }
+    if (listen(sockfd, args->nchannels + 1) < 0) {
+        virReportSystemError(errno, "%s", _("saveThread: listen() failed"));
+        goto cleanup;
+    }
+
+    /* signal that the server is ready */
+    if (safewrite(STDOUT_FILENO, &buf, 1) != 1) {
+        virReportSystemError(errno, "%s", _("saveThread: safewrite failed"));
+        goto cleanup;
+    }
+
+    for (idx = 0; idx < args->nchannels + 1; idx++) {
+        /* Wait for incoming connection. */
+        multiFdConnData *c = &args->conn[idx];
+        if ((c->clientfd = accept(sockfd, NULL, NULL)) < 0) {
+            virReportSystemError(errno, "%s", _("saveThread: accept() failed"));
+            goto cleanup;
+        }
+        if (virThreadCreate(&c->tid, true, &clientThreadFunc, c) < 0) {
+            virReportSystemError(errno, "%s", _("saveThread: client thread creation failed"));
+            goto cleanup;
+        }
+    }
+
+    args->total = waitClientThreads(args->conn, args->nchannels + 1);
+
+ cleanup:
+    for (idx = 0; idx < args->nchannels + 1; idx++) {
+        multiFdConnData *c = &args->conn[idx];
+        VIR_FORCE_CLOSE(c->clientfd);
+    }
+    if (VIR_CLOSE(sockfd) < 0)
+        args->total = -1;
+}
+
+static const char *program_name;
+
+G_GNUC_NORETURN static void
+usage(int status)
+{
+    if (status) {
+        fprintf(stderr, _("%s: try --help for more details"), program_name);
+    } else {
+        fprintf(stderr, _("Usage: %s UNIX_SOCNAME N MAINFD FD0 FD1 ... FDn"), program_name);
+    }
+    exit(status);
+}
+
+int
+main(int argc, char **argv)
+{
+    virThread tid;
+    virThreadFunc func = saveThreadFunc;
+    multiFdThreadArgs args = { 0 };
+    int idx;
+
+    /* sleep(10); */
+
+    program_name = argv[0];
+
+    if (virGettextInitialize() < 0 ||
+        virErrorInitialize() < 0) {
+        fprintf(stderr, _("%s: initialization failed"), program_name);
+        exit(EXIT_FAILURE);
+    }
+
+    if (argc > 1 && STREQ(argv[1], "--help"))
+        usage(EXIT_SUCCESS);
+    if (argc < 4)
+        usage(EXIT_FAILURE);
+
+    args.sun_path = argv[1];
+    if (virStrToLong_i(argv[2], NULL, 10, &args.nchannels) < 0)
+        fprintf(stderr, _("%s: malformed number of channels N %s"), program_name, argv[2]);
+
+    if (argc < 4 + args.nchannels)
+        usage(EXIT_FAILURE);
+
+    args.conn = g_new0(multiFdConnData, args.nchannels + 1);
+
+    for (idx = 3; idx < 3 + args.nchannels + 1; idx++) {
+        multiFdConnData *c = &args.conn[idx - 3];
+
+        if (virStrToLong_i(argv[idx], NULL, 10, &c->filefd) < 0) {
+            fprintf(stderr, _("%s: malformed FD %s"), program_name, argv[idx]);
+            usage(EXIT_FAILURE);
+        }
+#ifndef F_GETFL
+#error "multifd-helper requires F_GETFL parameter of fcntl"
+#endif
+        c->oflags = fcntl(c->filefd, F_GETFL);
+        if ((c->oflags & O_ACCMODE) == O_RDONLY) {
+            func = loadThreadFunc;
+        }
+    }
+
+    /* initialize server address structure */
+    memset(&args.serv_addr, 0, sizeof(args.serv_addr));
+    args.serv_addr.sun_family = AF_UNIX;
+    virStrcpyStatic(args.serv_addr.sun_path, args.sun_path);
+
+    if (virThreadCreate(&tid, true, func, &args) < 0) {
+        virReportSystemError(errno, _("%s: failed to create server thread"), program_name);
+        exit(EXIT_FAILURE);
+    }
+
+    if (virThreadJoinRet(&tid) < 0)
+        exit(EXIT_FAILURE);
+
+    if (args.total < 0)
+        exit(EXIT_FAILURE);
+
+    exit(EXIT_SUCCESS);
+}
diff --git a/src/util/virthread.c b/src/util/virthread.c
index 5422bb74fd..0f6c6a68fa 100644
--- a/src/util/virthread.c
+++ b/src/util/virthread.c
@@ -348,6 +348,11 @@ void virThreadJoin(virThread *thread)
     pthread_join(thread->thread, NULL);
 }
 
+int virThreadJoinRet(virThread *thread)
+{
+    return pthread_join(thread->thread, NULL);
+}
+
 void virThreadCancel(virThread *thread)
 {
     pthread_cancel(thread->thread);
diff --git a/src/util/virthread.h b/src/util/virthread.h
index 23abe0b6c9..5cecb9bd8a 100644
--- a/src/util/virthread.h
+++ b/src/util/virthread.h
@@ -89,6 +89,7 @@ int virThreadCreateFull(virThread *thread,
 void virThreadSelf(virThread *thread);
 bool virThreadIsSelf(virThread *thread);
 void virThreadJoin(virThread *thread);
+int virThreadJoinRet(virThread *thread);
 
 size_t virThreadMaxName(void);
 
-- 
2.35.3





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