The libblkid (since v1.41.1) returns private device-mapper names (e.g.
/dev/dm-0). It's because the probe_one() function scans /dev before
/dev/mapper.
brw-rw---- 1 root disk 253, 0 2009-04-27 13:41 /dev/dm-0
brw-rw---- 1 root disk 253, 0 2009-04-27 13:41 /dev/mapper/TestVolGroup-TestLogVolume
Old version:
# blkid -t LABEL="TEST-LABEL" -o device
/dev/dm-0
Fixed version:
# blkid -t LABEL="TEST-LABEL" -o device
/dev/mapper/TestVolGroup-TestLogVolume
Addresses-Red-Hat-Bug: #497259
Signed-off-by: Karel Zak <[email protected]>
---
lib/blkid/devname.c | 16 ++++++++++++----
1 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/lib/blkid/devname.c b/lib/blkid/devname.c
index 8553e9f..59c0919 100644
--- a/lib/blkid/devname.c
+++ b/lib/blkid/devname.c
@@ -179,6 +179,15 @@ static void probe_one(blkid_cache cache, const char *ptname,
if (dev && dev->bid_devno == devno)
goto set_pri;
+ /* Try to translate private device-mapper dm-<N> names
+ * to standard /dev/mapper/<name>.
+ */
+ if (!strncmp(ptname, "dm-", 3) && isdigit(ptname[3])) {
+ blkid__scan_dir("/dev/mapper", devno, 0, &devname);
+ if (devname)
+ goto get_dev;
+ }
+
/*
* Take a quick look at /dev/ptname for the device number. We check
* all of the likely device directories. If we don't find it, or if
@@ -197,17 +206,16 @@ static void probe_one(blkid_cache cache, const char *ptname,
if (stat(device, &st) == 0 && S_ISBLK(st.st_mode) &&
st.st_rdev == devno) {
devname = blkid_strdup(device);
- break;
+ goto get_dev;
}
}
- /* Do a short-cut scan of /dev/mapper first */
- if (!devname)
- blkid__scan_dir("/dev/mapper", devno, 0, &devname);
if (!devname) {
devname = blkid_devno_to_devname(devno);
if (!devname)
return;
}
+
+get_dev:
dev = blkid_get_dev(cache, devname, BLKID_DEV_NORMAL);
free(devname);
--
1.6.0.6
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 <[email protected]>
Signed-off-by: Karel Zak <[email protected]>
---
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
On Mon, Apr 27, 2009 at 03:00:57PM +0200, Karel Zak wrote:
> The libblkid (since v1.41.1) returns private device-mapper names (e.g.
> /dev/dm-0). It's because the probe_one() function scans /dev before
> /dev/mapper.
Checked in, thanks. Debian-derived distributions don't create
/dev/dm-X names, which is why I didn't notice this issue. However,
because of this, I modified your patch to keep this chunk which you removed:
> - /* Do a short-cut scan of /dev/mapper first */
> - if (!devname)
> - blkid__scan_dir("/dev/mapper", devno, 0, &devname);
For distributions that don't create /dev/dm-X devices, your check
above won't find the device name, so after searching /dev, we need to
do a short-cut scan of /dev/mapper before we do a full brute force
search via blkid_devno_to_devname.
- Ted
On Mon, Apr 27, 2009 at 03:00:58PM +0200, Karel Zak wrote:
> The Linux kernel (since 2.6.29, patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128)
> exports the real DM device names in /sys/block/<ptname>/dm/name.
Thanks, applied.
- Ted
On Sat, May 02, 2009 at 10:05:28PM -0400, Theodore Tso wrote:
> On Mon, Apr 27, 2009 at 03:00:57PM +0200, Karel Zak wrote:
> > The libblkid (since v1.41.1) returns private device-mapper names (e.g.
> > /dev/dm-0). It's because the probe_one() function scans /dev before
> > /dev/mapper.
>
> Checked in, thanks. Debian-derived distributions don't create
> /dev/dm-X names, which is why I didn't notice this issue. However,
> because of this, I modified your patch to keep this chunk which you removed:
You needn't this chunk.
> > - /* Do a short-cut scan of /dev/mapper first */
> > - if (!devname)
> > - blkid__scan_dir("/dev/mapper", devno, 0, &devname);
>
> For distributions that don't create /dev/dm-X devices, your check
I guess that all distributions have "dm-X" names in /proc/partitions, it
means my check
if (!strncmp(ptname, "dm-", 3) && isdigit(ptname[3]))
blkid__scan_dir("/dev/mapper", devno, 0, &devname);
works everywhere and you needn't to check /dev before /dev/mapper for
dm-X ptnames.
> above won't find the device name, so after searching /dev, we need to
> do a short-cut scan of /dev/mapper before we do a full brute force
> search via blkid_devno_to_devname.
Karel
--
Karel Zak <[email protected]>