The Linux kernel (since 2.6.29, patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128)
exports the real DM device names in /sys/block/<ptname>/dm/name.
The sysfs based solution is nicer and faster than scan for devno in
/dev/mapper/.
CC: Milan Broz <mbroz@xxxxxxxxxx>
Signed-off-by: Karel Zak <kzak@xxxxxxxxxx>
---
lib/blkid/devname.c | 28 +++++++++++++++++++++++++++-
1 files changed, 27 insertions(+), 1 deletions(-)
diff --git a/lib/blkid/devname.c b/lib/blkid/devname.c
index 59c0919..4dde766 100644
--- a/lib/blkid/devname.c
+++ b/lib/blkid/devname.c
@@ -153,6 +153,30 @@ static int is_dm_leaf(const char *devname)
}
/*
+ * Since 2.6.29 (patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128) kernel sysfs
+ * provides the real DM device names in /sys/block/<ptname>/dm/name
+ */
+static char *get_dm_name(const char *ptname)
+{
+ FILE *f;
+ size_t sz;
+ char path[256], name[256], *res = NULL;
+
+ snprintf(path, sizeof(path), "/sys/block/%s/dm/name", ptname);
+ if ((f = fopen(path, "r")) == NULL)
+ return NULL;
+
+ /* read "<name>\n" from sysfs */
+ if (fgets(name, sizeof(name), f) && (sz = strlen(name)) > 1) {
+ name[sz - 1] = '\0';
+ snprintf(path, sizeof(path), "/dev/mapper/%s", name);
+ res = blkid_strdup(path);
+ }
+ fclose(f);
+ return res;
+}
+
+/*
* Probe a single block device to add to the device cache.
*/
static void probe_one(blkid_cache cache, const char *ptname,
@@ -183,7 +207,9 @@ static void probe_one(blkid_cache cache, const char *ptname,
* to standard /dev/mapper/<name>.
*/
if (!strncmp(ptname, "dm-", 3) && isdigit(ptname[3])) {
- blkid__scan_dir("/dev/mapper", devno, 0, &devname);
+ devname = get_dm_name(ptname);
+ if (!devname)
+ blkid__scan_dir("/dev/mapper", devno, 0, &devname);
if (devname)
goto get_dev;
}
--
1.6.0.6
--
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