Re: [libvirt] [PATCH v2 1/3] util: Introduce virDevMapperGetTargets

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(a)redhat.com&gt; --- src/libvirt_private.syms | 4 ++ src/util/Makefile.inc.am | 2 + src/util/virdevmapper.c | 160 +++++++++++++++++++++++++++++++++++++++++++++++ src/util/virdevmapper.h | 32 ++++++++++ 4 files changed, 198 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..9717482da8 --- /dev/null +++ b/src/util/virdevmapper.c @@ -0,0 +1,160 @@ +/* + * 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(a)redhat.com&gt; + */ + +#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" + +#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) + +/** + * virDevMapperGetTargets: + * @path: multipath device + * @maj: returned array of MAJOR device numbers + * @min: returner array of MINOR device numbers + * @nmaj: number of items in @maj array + * + * For given @path figure out its targets, and store them in @maj + * and @min arrays. Both arrays have the same number of items + * upon return. + * + * If @path is not a multipath device, @ndevs is set to 0 and + * success is returned. + * + * 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, + unsigned int **maj, + unsigned int **min, + size_t *nmaj) +{ + struct dm_task *dmt = NULL; + struct dm_deps *deps; + struct dm_info info; + size_t i; + int ret = -1; + + *nmaj = 0; + + if (virDevMapperInitialize() < 0) + goto cleanup;

+ + if (!(dmt = dm_task_create(DM_DEVICE_DEPS))) + goto cleanup;

+ + if (!dm_task_set_name(dmt, path)) { + if (errno == ENOENT) { + /* It's okay, @path is not managed by devmapper => + * not a multipath 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(*maj, deps->count) < 0 || + VIR_ALLOC_N_QUIET(*min, deps->count) < 0) { + VIR_FREE(*maj); + goto cleanup; + } + *nmaj = deps->count; + + for (i = 0; i < deps->count; i++) { + (*maj)[i] = major(deps->device[i]); + (*min)[i] = minor(deps->device[i]); + } + + ret = 0; + cleanup: + dm_task_destroy(dmt);

+ return ret; +} + +#else /* ! WITH_DEVMAPPER */ + +int +virDevMapperGetTargets(const char *path ATTRIBUTE_UNUSED, + unsigned int **maj ATTRIBUTE_UNUSED, + unsigned int **min ATTRIBUTE_UNUSED, + size_t *nmaj 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..e88ac0f8ce --- /dev/null +++ b/src/util/virdevmapper.h @@ -0,0 +1,32 @@ +/* + * 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(a)redhat.com&gt; + */ + +#ifndef __VIR_DEVMAPPER_H__ +# define __VIR_DEVMAPPER_H__ + +int virDevMapperGetTargets(const char *path, + unsigned int **maj, + unsigned int **min, + size_t *nmaj);