From c66b76761528f6294849cacaa8a99c49967d0070 Mon Sep 17 00:00:00 2001

Message-Id: <c66b76761528f6294849cacaa8a99c49967d0070@dist-git>

From: Michal Privoznik <mprivozn@redhat.com>

Date: Mon, 9 Apr 2018 15:46:49 +0200

Subject: [PATCH] util: Introduce virDevMapperGetTargets

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https://bugzilla.redhat.com/show_bug.cgi?id=1564996

This helper fetches dependencies for given device mapper target.

At the same time, we need to provide a dummy log function because

by default libdevmapper prints out error messages to stderr which

we need to suppress.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

(cherry picked from commit fd9d1e686db64fa9481b9eab4dabafa46713e2cf)

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

Conflicts: src/util/Makefile.inc.am: src/Makefile split is not backported

  yet (9cd0bdd1a178a76dbce4)

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

Reviewed-by: Andrea Bolognani <abologna@redhat.com>

Reviewed-by: Ján Tomko <jtomko@redhat.com>

---

 src/Makefile.am          |   1 +

 src/libvirt_private.syms |   4 +

 src/util/virdevmapper.c  | 199 +++++++++++++++++++++++++++++++++++++++

 src/util/virdevmapper.h  |  31 ++++++

 4 files changed, 235 insertions(+)

 create mode 100644 src/util/virdevmapper.c

 create mode 100644 src/util/virdevmapper.h

diff --git a/src/Makefile.am b/src/Makefile.am

index 6b24a47afe..2130859045 100644

--- a/src/Makefile.am

+++ b/src/Makefile.am

@@ -111,6 +111,7 @@ UTIL_SOURCES =							\

 		util/virconf.c util/virconf.h			\

 		util/vircrypto.c util/vircrypto.h		\

 		util/virdbus.c util/virdbus.h util/virdbuspriv.h	\

+		util/virdevmapper.c util/virdevmapper.h \

 		util/virdnsmasq.c util/virdnsmasq.h		\

 		util/virebtables.c util/virebtables.h		\

 		util/virendian.h				\

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms

index 15cc83931a..5bacafb462 100644

--- a/src/libvirt_private.syms

+++ b/src/libvirt_private.syms

@@ -1625,6 +1625,10 @@ virDBusMessageUnref;

 virDBusSetSharedBus;

+# util/virdevmapper.h

+virDevMapperGetTargets;

+

+

 # util/virdnsmasq.h

 dnsmasqAddDhcpHost;

 dnsmasqAddHost;

diff --git a/src/util/virdevmapper.c b/src/util/virdevmapper.c

new file mode 100644

index 0000000000..d2c25af003

--- /dev/null

+++ b/src/util/virdevmapper.c

@@ -0,0 +1,199 @@

+/*

+ * virdevmapper.c: Functions for handling device mapper

+ *

+ * Copyright (C) 2018 Red Hat, Inc.

+ *

+ * 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/>.

+ *

+ * Authors:

+ *     Michal Privoznik <mprivozn@redhat.com>

+ */

+

+#include <config.h>

+

+#ifdef MAJOR_IN_MKDEV

+# include <sys/mkdev.h>

+#elif MAJOR_IN_SYSMACROS

+# include <sys/sysmacros.h>

+#endif

+

+#ifdef WITH_DEVMAPPER

+# include <libdevmapper.h>

+#endif

+

+#include "virdevmapper.h"

+#include "internal.h"

+#include "virthread.h"

+#include "viralloc.h"

+#include "virstring.h"

+

+#ifdef WITH_DEVMAPPER

+static void

+virDevMapperDummyLogger(int level ATTRIBUTE_UNUSED,

+                        const char *file ATTRIBUTE_UNUSED,

+                        int line ATTRIBUTE_UNUSED,

+                        int dm_errno ATTRIBUTE_UNUSED,

+                        const char *fmt ATTRIBUTE_UNUSED,

+                        ...)

+{

+    return;

+}

+

+static int

+virDevMapperOnceInit(void)

+{

+    /* Ideally, we would not need this. But libdevmapper prints

+     * error messages to stderr by default. Sad but true. */

+    dm_log_with_errno_init(virDevMapperDummyLogger);

+    return 0;

+}

+

+

+VIR_ONCE_GLOBAL_INIT(virDevMapper)

+

+

+static int

+virDevMapperGetTargetsImpl(const char *path,

+                           char ***devPaths_ret,

+                           unsigned int ttl)

+{

+    struct dm_task *dmt = NULL;

+    struct dm_deps *deps;

+    struct dm_info info;

+    char **devPaths = NULL;

+    char **recursiveDevPaths = NULL;

+    size_t i;

+    int ret = -1;

+

+    *devPaths_ret = NULL;

+

+    if (virDevMapperInitialize() < 0)

+        return ret;

+

+    if (ttl == 0) {

+        errno = ELOOP;

+        return ret;

+    }

+

+    if (!(dmt = dm_task_create(DM_DEVICE_DEPS)))

+        return ret;

+

+    if (!dm_task_set_name(dmt, path)) {

+        if (errno == ENOENT) {

+            /* It's okay, @path is not managed by devmapper =>

+             * not a devmapper device. */

+            ret = 0;

+        }

+        goto cleanup;

+    }

+

+    dm_task_no_open_count(dmt);

+

+    if (!dm_task_run(dmt))

+        goto cleanup;

+

+    if (!dm_task_get_info(dmt, &info))

+        goto cleanup;

+

+    if (!info.exists) {

+        ret = 0;

+        goto cleanup;

+    }

+

+    if (!(deps = dm_task_get_deps(dmt)))

+        goto cleanup;

+

+    if (VIR_ALLOC_N_QUIET(devPaths, deps->count + 1) < 0)

+        goto cleanup;

+

+    for (i = 0; i < deps->count; i++) {

+        if (virAsprintfQuiet(&devPaths[i], "/dev/block/%u:%u",

+                             major(deps->device[i]),

+                             minor(deps->device[i])) < 0)

+            goto cleanup;

+    }

+

+    recursiveDevPaths = NULL;

+    for (i = 0; i < deps->count; i++) {

+        char **tmpPaths;

+

+        if (virDevMapperGetTargetsImpl(devPaths[i], &tmpPaths, ttl - 1) < 0)

+            goto cleanup;

+

+        if (tmpPaths &&

+            virStringListMerge(&recursiveDevPaths, &tmpPaths) < 0) {

+            virStringListFree(tmpPaths);

+            goto cleanup;

+        }

+    }

+

+    if (virStringListMerge(&devPaths, &recursiveDevPaths) < 0)

+        goto cleanup;

+

+    VIR_STEAL_PTR(*devPaths_ret, devPaths);

+    ret = 0;

+ cleanup:

+    virStringListFree(recursiveDevPaths);

+    virStringListFree(devPaths);

+    dm_task_destroy(dmt);

+    return ret;

+}

+

+

+/**

+ * virDevMapperGetTargets:

+ * @path: devmapper target

+ * @devPaths: returned string list of devices

+ *

+ * For given @path figure out its targets, and store them in

+ * @devPaths array. Note, @devPaths is a string list so it's NULL

+ * terminated.

+ *

+ * If @path is not a devmapper device, @devPaths is set to NULL and

+ * success is returned.

+ *

+ * If @path consists of yet another devmapper targets these are

+ * consulted recursively.

+ *

+ * If we don't have permissions to talk to kernel, -1 is returned

+ * and errno is set to EBADF.

+ *

+ * Returns 0 on success,

+ *        -1 otherwise (with errno set, no libvirt error is

+ *        reported)

+ */

+int

+virDevMapperGetTargets(const char *path,

+                       char ***devPaths)

+{

+    const unsigned int ttl = 32;

+

+    /* Arbitrary limit on recursion level. A devmapper target can

+     * consist of devices or yet another targets. If that's the

+     * case, we have to stop recursion somewhere. */

+

+    return virDevMapperGetTargetsImpl(path, devPaths, ttl);

+}

+

+#else /* ! WITH_DEVMAPPER */

+

+int

+virDevMapperGetTargets(const char *path ATTRIBUTE_UNUSED,

+                       char ***devPaths ATTRIBUTE_UNUSED)

+{

+    errno = ENOSYS;

+    return -1;

+}

+#endif /* ! WITH_DEVMAPPER */

diff --git a/src/util/virdevmapper.h b/src/util/virdevmapper.h

new file mode 100644

index 0000000000..34d6655e77

--- /dev/null

+++ b/src/util/virdevmapper.h

@@ -0,0 +1,31 @@

+/*

+ * virdevmapper.h: Functions for handling device mapper

+ *

+ * Copyright (C) 2018 Red Hat, Inc.

+ *

+ * 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/>.

+ *

+ * Authors:

+ *     Michal Privoznik <mprivozn@redhat.com>

+ */

+

+#ifndef __VIR_DEVMAPPER_H__

+# define __VIR_DEVMAPPER_H__

+

+int

+virDevMapperGetTargets(const char *path,

+                       char ***devPaths);

+

+#endif /* __VIR_DEVMAPPER_H__ */

-- 

2.17.0