On 06/08/2013 01:04, David Sterba wrote:
On Mon, Jul 15, 2013 at 01:30:52PM +0800, Anand Jain wrote:
This patch adds --mapper option to btrfs device scan and
btrfs filesystem show cli, when used will look for btrfs
devs under /dev/mapper and will use the links provided
under the /dev/mapper.
In the long run I want the usage of /dev/mapper path
(along with /proc/partitions) be the default option to
scan for the btrfs devs. (/proc/partitions must be scanned
as well because to include the mapper blacklisted devs.)
Well, we want to avoid using own scanning and always consult the blkid
cache, so I'd rather stop adding user-visible changes to this command.
here is a test prog "t" (attached inline below) using blkid.
t picks up both non multipath path and mapper path as below.
----
# ./t
Device: /dev/sdb b03095dc-8eb5-40c9-8790-da6977110799
Device: /dev/sdc abc347f2-dfcc-46bf-a4ac-e21fba7ff1a3
Device: /dev/mapper/mpatha b03095dc-8eb5-40c9-8790-da6977110799
Device: /dev/mapper/mpathb abc347f2-dfcc-46bf-a4ac-e21fba7ff1a3
Found 4
------
However when
/etc/multipath.conf
defaults {
user_friendly_names no
}
then the mapper paths are not friendly enough to use
-------
# ./t
Device: /dev/sdb b03095dc-8eb5-40c9-8790-da6977110799
Device: /dev/sdc abc347f2-dfcc-46bf-a4ac-e21fba7ff1a3
Device: /dev/mapper/1ATA VBOX HARDDISK VB96b6139c-83f38bf1
b03095dc-8eb5-40c9-8790-da6977110799
Device: /dev/mapper/1ATA VBOX HARDDISK VBc6ab3781-f63da170
abc347f2-dfcc-46bf-a4ac-e21fba7ff1a3
Found 4
------
in this case the /dev/dm-<n> would have been better to use.
and our own scan does the better job here.. as it
reads /proc/partition and gives priority to dm-<n> paths
------
btrfs fi show
Label: none uuid: abc347f2-dfcc-46bf-a4ac-e21fba7ff1a3
Total devices 1 FS bytes used 28.00KiB
devid 1 size 2.00GiB used 240.75MiB path /dev/dm-1
Label: none uuid: b03095dc-8eb5-40c9-8790-da6977110799
Total devices 1 FS bytes used 28.00KiB
devid 1 size 1.98GiB used 238.25MiB path /dev/dm-0
-------
so as of now having our scan is better than blkid.
Now for the users who want to use the user friendly name
provided by mapper. the newly introduced option --mapper
which just looks under /dev/mapper will help.
Thanks, Anand
----------------t.c--------------
#include <stdio.h>
#include <blkid/blkid.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
main()
{
char *type;
char str[100];
int total = 0;
blkid_dev_iterate iter = NULL;
blkid_dev dev = NULL;
blkid_cache cache = NULL;
memset(str, '0', 100);
if (blkid_get_cache(&cache, 0) < 0)
return -1;
blkid_probe_all(cache);
iter = blkid_dev_iterate_begin(cache);
//blkid_dev_set_search(iter, NULL, NULL);
blkid_dev_set_search(iter, "TYPE", "btrfs");
while (blkid_dev_next(iter, &dev) == 0) {
dev = blkid_verify(cache, dev);
if (!dev)
continue;
else {
total++;
printf("Device: %s\t%s\n",
blkid_dev_devname(dev),
blkid_get_tag_value(cache,"UUID",
blkid_dev_devname(dev)));
}
}
blkid_dev_iterate_end(iter);
printf("Found %d\n", total);
return total;
}
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
