Non-unmountable file system

Non-unmountable file system

[Matthias Urlichs]

This is btrfs with kernel 3.19. (.0-trunk from Debian), on a single volume
(on top of LVM but that should not matter).

I do this, on a freshly-booted system:
# mount /foo
# cd foo
# rsync -aPHAX . /bar
[ after an hour or so ]
^C
# cd ..
# fuser -m /foo
# ps ax | grep "[ /]rsync"
# umount /foo
umount: /dev/mapper/data-foo: target is busy
# 

Any idea what could possible be going on here?


NB: "after an hour": no wonder, when I see this in strace:

11:41:51.929033 stat("cpool/0/0/5/0058f2c720f7567989a0f4d33e5c8eb4",
{st_mode=S_IFREG|0640, st_size=65, ...}) = 0 <0.000015>
11:41:51.929077 llistxattr("cpool/0/0/5/0058f2c720f7567989a0f4d33e5c8eb4",
"", 1024) = 0 <0.000025>
11:41:51.929130 lstat("cpool/0/0/5/005ee7df1e1fa3a7cf6cbbff5e25b1eb",
{st_mode=S_IFREG|0640, st_size=54, ...}) = 0 <0.598521> <<***!!!***
11:41:52.527730 getxattr("cpool/0/0/5/005ee7df1e1fa3a7cf6cbbff5e25b1eb",
"system.posix_acl_access", 0x7fff32f63090, 132) = -1 ENODATA (No data
available) <0.000022>
11:41:52.527829 stat("cpool/0/0/5/005ee7df1e1fa3a7cf6cbbff5e25b1eb",
{st_mode=S_IFREG|0640, st_size=54, ...}) = 0 <0.000016>

The directory in question has 300 entries and the disks on which this
filesystem resides are otherwise idle and do not report any errors, SMART or
otherwise.

https://bugzilla.kernel.org/show_bug.cgi?id=93781