[Bug 8566] umount: add support for the -O option

bugzilla at busybox.net bugzilla at busybox.net
Thu Nov 2 09:21:23 UTC 2017


https://bugs.busybox.net/show_bug.cgi?id=8566

Mukuntha Rajaa <mukuntharajaa at yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|1.24.x                      |1.27.x

--- Comment #1 from Mukuntha Rajaa <mukuntharajaa at yahoo.com> ---
Loop mount fails with "Device or resource busy". Mounting same device with
util-linux based mount, it succeeds.

# mount -o loop
/dev/VG_CFPU-0/config-R_FPT_180.0.1.36.WR.bcn.rm.1710290936.408465-INITIAL
/mnt/backup/
mount: mounting
/dev/VG_CFPU-0/config-R_FPT_180.0.1.36.WR.bcn.rm.1710290936.408465-INITIAL on
/mnt/backup/ failed: Device or resource busy

# ls -l
/dev/VG_CFPU-0/config-R_FPT_180.0.1.36.WR.bcn.rm.1710290936.408465-INITIAL-INITIAL
lrwxrwxrwx 1 root root 8 Oct 23 08:23
/dev/VG_CFPU-0/config-R_FPT_180.0.1.36.WR.bcn.rm.1710290936.408465-INITIAL ->
../dm-18


Util-linux mount:
# /tmp/mount -o loop
/dev/VG_CFPU-0/config-config-R_FPT_180.0.1.36.WR.bcn.rm.1710290936.408465-INITIAL
/mnt/backup
#

Looking at strace, util-linux is able to follow softlink to dm device and find
out the actual one from /dev/mapper/ and mount that device finally. This part
seems to be missing while I did strace on busybox mount

29730
readlink("/dev/VG_CFPU-0/config-R_FPT_180.0.1.34.WR.bcn.rm.1710220915.408367-INITIAL",
"../dm-18", 4095) = 8
29730 lstat("/dev/dm-18", {st_mode=S_IFBLK|0600, st_rdev=makedev(254, 18),
...}) = 0
29730 stat("/dev/dm-18", {st_mode=S_IFBLK|0600, st_rdev=makedev(254, 18), ...})
= 0
29730 open("/sys/block/dm-18/dm/name", O_RDONLY|O_CLOEXEC) = 3
29730 fstat(3, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
29730 read(3,
"VG_CFPU--0-config--R_FPT_180.0.1.34.WR.bcn.rm.1710220915.408367--INITIAL\n",
4096) = 73
29730
access("/dev/mapper/VG_CFPU--0-config--R_FPT_180.0.1.34.WR.bcn.rm.1710220915.408367--INITIAL",
F_OK) = 0
29730
stat("/dev/mapper/VG_CFPU--0-config--R_FPT_180.0.1.34.WR.bcn.rm.1710220915.408367--INITIAL",
{st_mode=S_IFBLK|0600, st_rdev=makedev(254, 18), ...}) = 0

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