libmp_mapinfo() is intended as a generic abstraction for retrieving information from
the kernel device-mapper driver. It retrieves the information that the caller
needs, with a minimal set of DM ioctls, and never more then 2 ioctl calls.
libdm's DM_DEVICE_TABLE and DM_DEVICE_STATUS calls map to the kernel's
DM_TABLE_STATUS ioctl, with or without the DM_STATUS_TABLE_FLAG set,
respectively. DM_TABLE_STATUS always retrieves the basic map status (struct
dm_info) and the map UUID and name, too.
Note: I'd prefer to use an unnamed struct instead of _u in
union libmp_map_identifer. But doing using an unnamed struct and and
initializing the union like this in a function argument:
func((mapid_t) { .major = major, .minor = minor })
is not part of C99, and not supported in gcc 4.8, which we still support.
Likewise, the following syntax for initializing an empty struct:
(mapinfo_t) { 0 }
is not supported on all architectures we support (notably clang 3.5 under
Debian Jessie).
Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
libmultipath/devmapper.c | 194 +++++++++++++++++++++++++++++-
libmultipath/devmapper.h | 70 +++++++++++
libmultipath/libmultipath.version | 3 +-
3 files changed, 265 insertions(+), 2 deletions(-)
diff --git a/libmultipath/devmapper.c b/libmultipath/devmapper.c
index 5492a86..f90a8df 100644
--- a/libmultipath/devmapper.c
+++ b/libmultipath/devmapper.c
@@ -14,7 +14,6 @@
#include <errno.h>
#include <syslog.h>
#include <sys/sysmacros.h>
-#include <linux/dm-ioctl.h>
#include "util.h"
#include "vector.h"
@@ -604,6 +603,199 @@ has_dm_info(const struct multipath *mpp)
return (mpp && mpp->dmi.exists != 0);
}
+static int libmp_set_map_identifier(int flags, mapid_t id, struct dm_task *dmt)
+{
+ switch (flags & __DM_MAP_BY_MASK) {
+ case DM_MAP_BY_UUID:
+ if (!id.str || !(*id.str))
+ return 0;
+ return dm_task_set_uuid(dmt, id.str);
+ case DM_MAP_BY_NAME:
+ if (!id.str || !(*id.str))
+ return 0;
+ return dm_task_set_name(dmt, id.str);
+ case DM_MAP_BY_DEV:
+ if (!dm_task_set_major(dmt, id._u.major))
+ return 0;
+ return dm_task_set_minor(dmt, id._u.minor);
+ case DM_MAP_BY_DEVT:
+ if (!dm_task_set_major(dmt, major(id.devt)))
+ return 0;
+ return dm_task_set_minor(dmt, minor(id.devt));
+ default:
+ condlog(0, "%s: invalid by_id", __func__);
+ return 0;
+ }
+}
+
+static int libmp_mapinfo__(int flags, mapid_t id, mapinfo_t info, const char *map_id)
+{
+ /* avoid libmp_mapinfo__ in log messages */
+ static const char fname__[] = "libmp_mapinfo";
+ struct dm_task __attribute__((cleanup(cleanup_dm_task))) *dmt = NULL;
+ struct dm_info dmi;
+ int rc, ioctl_nr;
+ uint64_t start, length = 0;
+ char *target_type = NULL, *params = NULL;
+ const char *name = NULL, *uuid = NULL;
+ char __attribute__((cleanup(cleanup_charp))) *tmp_target = NULL;
+ char __attribute__((cleanup(cleanup_charp))) *tmp_status = NULL;
+ bool tgt_set = false;
+
+ /*
+ * If both info.target and info.status are set, we need two
+ * ioctls. Call this function recursively.
+ * If successful, tmp_target will be non-NULL.
+ */
+ if (info.target && info.status) {
+ rc = libmp_mapinfo__(flags, id,
+ (mapinfo_t) { .target = &tmp_target },
+ map_id);
+ if (rc != DMP_OK)
+ return rc;
+ tgt_set = true;
+ }
+
+ /*
+ * The DM_DEVICE_TABLE and DM_DEVICE_STATUS ioctls both fetch the basic
+ * information from DM_DEVICE_INFO, too.
+ * Choose the most lightweight ioctl to fetch all requested info.
+ */
+ if (info.target && !info.status)
+ ioctl_nr = DM_DEVICE_TABLE;
+ else if (info.status || info.size || flags & __MAPINFO_TGT_TYPE)
+ ioctl_nr = DM_DEVICE_STATUS;
+ else
+ ioctl_nr = DM_DEVICE_INFO;
+
+ if (!(dmt = libmp_dm_task_create(ioctl_nr)))
+ return DMP_ERR;
+
+ if (!libmp_set_map_identifier(flags, id, dmt)) {
+ condlog(2, "%s: failed to set map identifier to %s", fname__, map_id);
+ return DMP_ERR;
+ }
+
+ if (!libmp_dm_task_run(dmt)) {
+ dm_log_error(3, ioctl_nr, dmt);
+ if (dm_task_get_errno(dmt) == ENXIO) {
+ condlog(2, "%s: map %s not found", fname__, map_id);
+ return DMP_NOT_FOUND;
+ } else
+ return DMP_ERR;
+ }
+
+ condlog(4, "%s: DM ioctl %d succeeded for %s",
+ fname__, ioctl_nr, map_id);
+
+ if (!dm_task_get_info(dmt, &dmi)) {
+ condlog(2, "%s: dm_task_get_info() failed for %s ", fname__, map_id);
+ return DMP_ERR;
+ } else if(!dmi.exists) {
+ condlog(2, "%s: map %s doesn't exist", fname__, map_id);
+ return DMP_NOT_FOUND;
+ }
+
+ if (info.target || info.status || info.size || flags & __MAPINFO_TGT_TYPE) {
+ if (dm_get_next_target(dmt, NULL, &start, &length,
+ &target_type, ¶ms) != NULL) {
+ condlog(2, "%s: map %s has multiple targets", fname__, map_id);
+ return DMP_NOT_FOUND;
+ }
+ if (!params) {
+ condlog(2, "%s: map %s has no targets", fname__, map_id);
+ return DMP_NOT_FOUND;
+ }
+ if (flags & __MAPINFO_TGT_TYPE) {
+ const char *tgt_type = flags & MAPINFO_MPATH_ONLY ? TGT_MPATH : TGT_PART;
+
+ if (strcmp(target_type, tgt_type)) {
+ condlog(3, "%s: target type mismatch: \"%s\" != \"%s\"",
+ fname__, tgt_type, target_type);
+ return DMP_NO_MATCH;
+ }
+ }
+ }
+
+ /*
+ * Check possible error conditions.
+ * If error is returned, don't touch any output parameters.
+ */
+ if ((info.name && !(name = dm_task_get_name(dmt)))
+ || (info.uuid && !(uuid = dm_task_get_uuid(dmt)))
+ || (info.status && !(tmp_status = strdup(params)))
+ || (info.target && !tmp_target && !(tmp_target = strdup(params))))
+ return DMP_ERR;
+
+ if (info.name) {
+ strlcpy(info.name, name, WWID_SIZE);
+ condlog(4, "%s: %s: name: \"%s\"", fname__, map_id, info.name);
+ }
+ if (info.uuid) {
+ strlcpy(info.uuid, uuid, DM_UUID_LEN);
+ condlog(4, "%s: %s: uuid: \"%s\"", fname__, map_id, info.uuid);
+ }
+
+ if (info.size) {
+ *info.size = length;
+ condlog(4, "%s: %s: size: %lld", fname__, map_id, *info.size);
+ }
+
+ if (info.dmi) {
+ memcpy(info.dmi, &dmi, sizeof(*info.dmi));
+ condlog(4, "%s: %s %d:%d, %d targets, %s table, %s, %s, %d opened, %u events",
+ fname__, map_id,
+ info.dmi->major, info.dmi->minor,
+ info.dmi->target_count,
+ info.dmi->live_table ? "live" :
+ info.dmi->inactive_table ? "inactive" : "no",
+ info.dmi->suspended ? "suspended" : "active",
+ info.dmi->read_only ? "ro" : "rw",
+ info.dmi->open_count,
+ info.dmi->event_nr);
+ }
+
+ if (info.target) {
+ *info.target = steal_ptr(tmp_target);
+ if (!tgt_set)
+ condlog(4, "%s: %s: target: \"%s\"", fname__, map_id, *info.target);
+ }
+
+ if (info.status) {
+ *info.status = steal_ptr(tmp_status);
+ condlog(4, "%s: %s: status: \"%s\"", fname__, map_id, *info.status);
+ }
+
+ return DMP_OK;
+}
+
+/* Helper: format a string describing the map for log messages */
+static const char* libmp_map_identifier(int flags, mapid_t id, char buf[BLK_DEV_SIZE])
+{
+ switch (flags & __DM_MAP_BY_MASK) {
+ case DM_MAP_BY_NAME:
+ case DM_MAP_BY_UUID:
+ return id.str;
+ case DM_MAP_BY_DEV:
+ safe_snprintf(buf, BLK_DEV_SIZE, "%d:%d", id._u.major, id._u.minor);
+ return buf;
+ case DM_MAP_BY_DEVT:
+ safe_snprintf(buf, BLK_DEV_SIZE, "%d:%d", major(id.devt), minor(id.devt));
+ return buf;
+ default:
+ safe_snprintf(buf, BLK_DEV_SIZE, "*invalid*");
+ return buf;
+ }
+}
+
+int libmp_mapinfo(int flags, mapid_t id, mapinfo_t info)
+{
+ char idbuf[BLK_DEV_SIZE];
+
+ return libmp_mapinfo__(flags, id, info,
+ libmp_map_identifier(flags, id, idbuf));
+}
+
int
dm_get_info(const char *name, struct dm_info *info)
{
diff --git a/libmultipath/devmapper.h b/libmultipath/devmapper.h
index 9438c2d..4ccaaa7 100644
--- a/libmultipath/devmapper.h
+++ b/libmultipath/devmapper.h
@@ -1,5 +1,6 @@
#ifndef _DEVMAPPER_H
#define _DEVMAPPER_H
+#include <linux/dm-ioctl.h>
#include "autoconfig.h"
#include "structs.h"
@@ -31,8 +32,77 @@ enum {
DMP_ERR,
DMP_OK,
DMP_NOT_FOUND,
+ DMP_NO_MATCH,
};
+/**
+ * enum mapinfo_flags: input flags for libmp_mapinfo()
+ */
+enum __mapinfo_flags {
+ /** DM_MAP_BY_NAME: identify map by device-mapper name from @name */
+ DM_MAP_BY_NAME = 0,
+ /** DM_MAP_BY_UUID: identify map by device-mapper UUID from @uuid */
+ DM_MAP_BY_UUID,
+ /** DM_MAP_BY_DEV: identify map by major/minor number from @dmi */
+ DM_MAP_BY_DEV,
+ /** DM_MAP_BY_DEVT: identify map by a dev_t */
+ DM_MAP_BY_DEVT,
+ __DM_MAP_BY_MASK = (1 << 8) - 1,
+ /* Fail if target type is not multipath */
+ MAPINFO_MPATH_ONLY = (1 << 8),
+ /* Fail if target type is not "partition" (linear) */
+ MAPINFO_PART_ONLY = (1 << 9),
+ __MAPINFO_TGT_TYPE = (MAPINFO_MPATH_ONLY | MAPINFO_PART_ONLY),
+};
+
+typedef union libmp_map_identifier {
+ const char *str;
+ struct {
+ int major;
+ int minor;
+ } _u;
+ dev_t devt;
+} mapid_t;
+
+typedef struct libmp_map_info {
+ /** @name: name of the map.
+ * If non-NULL, it must point to an array of WWID_SIZE bytes
+ */
+ char *name;
+ /** @uuid: UUID of the map.
+ * If non-NULL it must point to an array of DM_UUID_LEN bytes
+ */
+ char *uuid;
+ /** @dmi: Basic info, must point to a valid dm_info buffer if non-NULL */
+ struct dm_info *dmi;
+ /** @target: target params, *@target will be allocated if @target is non-NULL*/
+ char **target;
+ /** @size: target size. */
+ unsigned long long *size;
+ /** @status: target status, *@status will be allocated if @status is non-NULL */
+ char **status;
+} mapinfo_t;
+
+/**
+ * libmp_mapinfo(): obtain information about a map from the kernel
+ * @param flags: see __mapinfo_flags above.
+ * Exactly one of DM_MAP_BY_NAME, DM_MAP_BY_UUID, and DM_MAP_BY_DEV must be set.
+ * @param id: string or major/minor to identify the map to query
+ * @param info: output parameters, see above. Non-NULL elements will be filled in.
+ * @returns:
+ * DMP_OK if successful.
+ * DMP_NOT_FOUND if the map wasn't found, or has no or multiple targets.
+ * DMP_NO_MATCH if the map didn't match @tgt_type (see above).
+ * DMP_ERR if some other error occurred.
+ *
+ * This function obtains the requested information for the device-mapper map
+ * identified by the input parameters.
+ * Output parameters are only filled in if the return value is DMP_OK.
+ * For target / status / size information, the map's table should contain
+ * only one target (usually multipath or linear).
+ */
+int libmp_mapinfo(int flags, mapid_t id, mapinfo_t info);
+
int dm_prereq(unsigned int *v);
void skip_libmp_dm_init(void);
void libmp_dm_exit(void);
diff --git a/libmultipath/libmultipath.version b/libmultipath/libmultipath.version
index f58cb1d..48c2b67 100644
--- a/libmultipath/libmultipath.version
+++ b/libmultipath/libmultipath.version
@@ -43,7 +43,7 @@ LIBMPATHCOMMON_1.0.0 {
put_multipath_config;
};
-LIBMULTIPATH_24.0.0 {
+LIBMULTIPATH_25.0.0 {
global:
/* symbols referenced by multipath and multipathd */
add_foreign;
@@ -134,6 +134,7 @@ global:
libmp_get_version;
libmp_get_multipath_config;
libmp_dm_task_run;
+ libmp_mapinfo;
libmp_put_multipath_config;
libmp_udev_set_sync_support;
libmultipath_exit;
--
2.45.2
