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>
---
src/libvirt_private.syms | 4 +
src/util/Makefile.inc.am | 2 +
src/util/virdevmapper.c | 200 +++++++++++++++++++++++++++++++++++++++++++++++
src/util/virdevmapper.h | 31 ++++++++
4 files changed, 237 insertions(+)
create mode 100644 src/util/virdevmapper.c
create mode 100644 src/util/virdevmapper.h
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 03fe3b315f..3b7a19cff1 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1669,6 +1669,10 @@ virDBusMessageUnref;
virDBusSetSharedBus;
+# util/virdevmapper.h
+virDevMapperGetTargets;
+
+
# util/virdnsmasq.h
dnsmasqAddDhcpHost;
dnsmasqAddHost;
diff --git a/src/util/Makefile.inc.am b/src/util/Makefile.inc.am
index a3c3b711fd..9624fb687c 100644
--- a/src/util/Makefile.inc.am
+++ b/src/util/Makefile.inc.am
@@ -35,6 +35,8 @@ UTIL_SOURCES = \
util/virdbus.c \
util/virdbus.h \
util/virdbuspriv.h \
+ util/virdevmapper.c \
+ util/virdevmapper.h \
util/virdnsmasq.c \
util/virdnsmasq.h \
util/virebtables.c \
diff --git a/src/util/virdevmapper.c b/src/util/virdevmapper.c
new file mode 100644
index 0000000000..9491848f48
--- /dev/null
+++ b/src/util/virdevmapper.c
@@ -0,0 +1,200 @@
+/*
+ * virdevmapper.c: Functions for handling devmapper
+ *
+ * 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) {
+ 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 = 4;
+
+ /* 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. My dice chose
+ * four. */
+
+ 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..83ec03bd4e
--- /dev/null
+++ b/src/util/virdevmapper.h
@@ -0,0 +1,31 @@
+/*
+ * virdevmapper.h: Functions for handling devmapper
+ *
+ * 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__ */
--
2.16.1
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On Tue, Apr 03, 2018 at 11:03:25 +0200, Michal Privoznik wrote:
> 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>
> ---
> src/libvirt_private.syms | 4 +
> src/util/Makefile.inc.am | 2 +
> src/util/virdevmapper.c | 200 +++++++++++++++++++++++++++++++++++++++++++++++
> src/util/virdevmapper.h | 31 ++++++++
> 4 files changed, 237 insertions(+)
> create mode 100644 src/util/virdevmapper.c
> create mode 100644 src/util/virdevmapper.h
[...]
> diff --git a/src/util/virdevmapper.c b/src/util/virdevmapper.c
> new file mode 100644
> index 0000000000..9491848f48
> --- /dev/null
> +++ b/src/util/virdevmapper.c
> @@ -0,0 +1,200 @@
> +/*
> + * virdevmapper.c: Functions for handling devmapper
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>
[...]
> +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) {
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) {
So these report libvirt errors, but don't mess them up. And only in case
of OOM, so this is fine.
> + 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 = 4;
So even trivial setups (dmcrypt + LVM) would exhaust half of your limit
for the device mapper block devices, and would still recurse one more
level to check the backing block device. I think we need some more
headroom here. I'd go with 16 or 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. My dice chose
> + * four. */
Drop the last sentence of this comment.
> +
> + return virDevMapperGetTargetsImpl(path, devPaths, ttl);
> +}
> +
ACK if you fix the condition syntax, raise the recursion level
significantly, and tweak the comment.
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