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From: Christoph Pleger <christoph.pleger@cs.uni-dortmund.de>
To: linux-lvm@redhat.com
Subject: Re: [linux-lvm] dmsetup says "Device does not exist", though it exists
Date: Wed, 14 Aug 2019 09:22:32 +0200	[thread overview]
Message-ID: <0f1ce51503d454e2068d9e0f65947273@cs.uni-dortmund.de> (raw)
In-Reply-To: <7f6f03e1-dbb1-971c-7f1f-f6c380a16b77@redhat.com>

[-- Attachment #1: Type: text/plain, Size: 1683 bytes --]

Hello,

>> I have a volume group with 20 logical volumes. Only the last one of 
>> these volumes has a strange problem with dmsetup, shown by these 
>> commands and output on the command line:
>> 
>> root@host:/home/linux# /sbin/dmsetup info -c -o name --noheadings 
>> /dev/vg/lv20
>> Device does not exist.
>> Command failed
>> 
>> root@host:/home/linux# lvdisplay -c /dev/vg/lv20
>>    /dev/vg/lv20:vg:3:1:-1:0:4194304:512:-1:0:-1:253:19
>> 
>> root@host:/home/linux# mount /dev/vg/lv20 /mnt
>> root@host:/home/linux# ls /mnt
>> lost+found data1 data2
>> 
>> That is, dmsetup says "Device does not exist" about a logical volume, 
>> though the volume exists and is operating normally. What is the 
>> possible problem here?
>> 

> 
> Have you tried  strace ?

I attached the relevant lines of the strace output. I am really 
wondering what is happening there:

1. A stat() on /dev/mapper/lv20 is performed, though I requested 
/dev/mapper/vg-lv20
2. A stat() on/dev/mapper/vg-lv15-real is performed. What does this have 
to do with lv20 (after I wrote what is at number 3, I know)
3. I do not even know where /dev/mapper/vg-lv15-real is coming from. I 
created a logical volume named lv15, but none named lv15-real. And 
really, 'ls -l /dev/vg/' does not list lv15-real, but 'ls -l 
/dev/mapper' lists vg-lv15-real and shows that is has the same link 
target /dev/dm-18 as lv20.
4. Though stat() found /dev/mapper/vg-lv15-real, ioctl() says that this 
device does not exist.


> Kernel version, lvm version,  distribution... ?

Kernel Debian amd64 4.9.168-1+deb9u2, LVM version 2.03.02(2), Debian 9 
(stretch)

Regards
   Christoph

[-- Attachment #2: strace.txt --]
[-- Type: text/plain, Size: 1152 bytes --]

ioctl(3, DM_VERSION, {version=4.0.0, data_size=16384, flags=DM_EXISTS_FLAG} => {version=4.35.0, data_size=16384, flags=DM_EXISTS_FLAG}) = 0
stat("/dev/vg/lv20", {st_mode=S_IFBLK|0660, st_rdev=makedev(253, 18), ...}) = 0
stat("/dev/mapper/lv20", 0x7ffd1b0ce0d0) = -1 ENOENT (No such file or directory)
open("/dev/mapper", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 4
fstat(4, {st_mode=S_IFDIR|0755, st_size=460, ...}) = 0
getdents(4, /* 23 entries */, 32768)    = 992
stat("/dev/mapper/vg-lv15-real", {st_mode=S_IFBLK|0660, st_rdev=makedev(253, 18), ...}) = 0
close(4)                                = 0
ioctl(3, DM_DEV_STATUS, {version=4.0.0, data_size=16384, name="vg-lv15-real", flags=DM_EXISTS_FLAG} => {version=4.35.0, data_size=16384, name="vg-lv15-real", flags=DM_EXISTS_FLAG}) = -1 ENXIO (No such device or address)
write(2, "Device does not exist.", 22Device does not exist.)  = 22
write(2, "\n", 1
)                       = 1
write(2, "Command failed.", 15Command failed.)         = 15
write(2, "\n", 1
)                       = 1
close(3)                                = 0
exit_group(1)                           = ?
+++ exited with 1 +++

  parent reply	other threads:[~2019-08-14  7:22 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-13  7:11 [linux-lvm] dmsetup says "Device does not exist", though it exists Christoph Pleger
2019-08-13 13:54 ` Zdenek Kabelac
2019-08-13 21:25   ` Bernd Eckenfels
2019-08-14 11:09     ` Zdenek Kabelac
2019-08-14  7:22   ` Christoph Pleger [this message]
2019-08-14 11:07     ` Zdenek Kabelac
2019-08-14 12:49       ` Christoph Pleger
2019-08-14 13:06       ` Christoph Pleger

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