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Bug 1566390 - [RHEL-7.5] losetup can not detach all loop devices
Summary: [RHEL-7.5] losetup can not detach all loop devices
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: util-linux
Version: 7.5
Hardware: x86_64
OS: Linux
unspecified
high
Target Milestone: rc
: ---
Assignee: Karel Zak
QA Contact: Radka Brychtova
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2018-04-12 08:39 UTC by xhe@redhat.com
Modified: 2018-10-30 10:53 UTC (History)
1 user (show)

Fixed In Version: util-linux-2.23.2-56.el7
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2018-10-30 10:52:39 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2018:3178 0 None None None 2018-10-30 10:53:27 UTC

Description xhe@redhat.com 2018-04-12 08:39:46 UTC 
Description of problem:
[RHEL-7.5] losetup can not detach all loop devices

Version-Release number of selected component (if applicable):
util-linux-2.23.2-52.el7.x86_64

How reproducible:
often

Steps to Reproduce:
1. losetup /dev/loopx -f /tmp/tfile_loopx
2. losetup -d
3. losetup -a

Actual results:
# losetup --all
/dev/loop0: [64768]:1001699 (/tmp/tfile_loop0)
/dev/loop2: [64768]:1001699 (/tmp/tfile_loop0)
/dev/loop8: [64768]:1001681 (/tmp/tfile_loop1)
# losetup -D
# losetup --all
/dev/loop0: [64768]:1001699 (/tmp/tfile_loop0)
/dev/loop2: [64768]:1001699 (/tmp/tfile_loop0)

# strace losetup -d /dev/loop2
execve("/usr/sbin/losetup", ["losetup", "-d", "/dev/loop2"], [/* 39 vars */]) = 0
brk(NULL)                               = 0x1f88000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f72200dc000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=44171, ...}) = 0
mmap(NULL, 44171, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f72200d1000
close(3)                                = 0
open("/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\340$\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=2151832, ...}) = 0
mmap(NULL, 3981792, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f721faef000
mprotect(0x7f721fcb2000, 2093056, PROT_NONE) = 0
mmap(0x7f721feb1000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1c2000) = 0x7f721feb1000
mmap(0x7f721feb7000, 16864, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f721feb7000
close(3)                                = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f72200d0000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f72200ce000
arch_prctl(ARCH_SET_FS, 0x7f72200ce740) = 0
mprotect(0x7f721feb1000, 16384, PROT_READ) = 0
mprotect(0x611000, 4096, PROT_READ)     = 0
mprotect(0x7f72200dd000, 4096, PROT_READ) = 0
munmap(0x7f72200d1000, 44171)           = 0
brk(NULL)                               = 0x1f88000
brk(0x1fa9000)                          = 0x1fa9000
brk(NULL)                               = 0x1fa9000
open("/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=106070960, ...}) = 0
mmap(NULL, 106070960, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f72195c6000
close(3)                                = 0
stat("/sys/block", {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
uname({sysname="Linux", nodename="storageqe-52.rhts.eng.pek2.redhat.com", ...}) = 0
stat("/dev/loop-control", {st_mode=S_IFCHR|0660, st_rdev=makedev(10, 237), ...}) = 0
open("/dev/loop2", O_RDONLY|O_CLOEXEC)  = 3
ioctl(3, LOOP_CLR_FD)                   = 0
close(3)                                = 0
close(1)                                = 0
close(2)                                = 0
exit_group(0)                           = ?
+++ exited with 0 +++

# losetup --all
/dev/loop0: [64768]:1001699 (/tmp/tfile_loop0)
/dev/loop2: [64768]:1001699 (/tmp/tfile_loop0)


Expected results:


Additional info:
Comment 2 Karel Zak 2018-04-13 09:43:39 UTC 
This is nothing unusual, if there is some reader of the loop device than kernel does not destroy the device, but mark by LO_FLAGS_AUTOCLEAR. The device will be 
detached later when reference counting will be zero.

As you can see from the strace than 

  ioctl(3, LOOP_CLR_FD)                   = 0

kernel returns success, in this case losetup cannot do anything more.

man losetup (upstream):

       -d, --detach loopdev...
              Detach  the  file  or device associated with the specified loop device(s). Note that since Linux v3.7 kernel uses "lazy device destruction".  The detach operation does not
              return EBUSY error anymore if device is actively used by system, but it is marked by autoclear flag and destroyed later.


Maybe  we can add this note to RHEL7.6 too.
Comment 8 errata-xmlrpc 2018-10-30 10:52:39 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:3178
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