Re: [PATCH] tests: add btrfs mount tests (fails!)

[Stanislav Brabec <sbrabec@suse.cz>]

Karel Zak wrote:
> On Tue, Feb 02, 2016 at 09:14:48PM +0100, Stanislav Brabec wrote:
>> Stanislav Brabec wrote:
>> +mkdir -p s3/bind-mnt
>
> So, this is enough to fix the testcase, right? I'd like to merge it.
>
>      Karel
>
Well, not.


There are missing umount commands in the middle of the test, which 
trigger following problem:

truncate -s10M source.img
mkdir -p /source/subdir
mkdir -p /dest
/sbin/mkfs.ext4 source.img
losetup /dev/loop0 $PWD/source.img
mount -text4 /dev/loop0 /source
mkdir -p /source/subdir
mount -o bind /source /dest
mount -o bind /source/subdir /dest

Mounting a bind mount over a root of existing bind mount causes mounting 
over the bind mount source. I expected mounting over the target 
directory I specified.

I am not sure, whether it is correct behavior, but for sure it is 
surprising.


Additionally, I am working on a reproducer of an invalid "mount -a" 
behavior triggered by kernel bug reporting false subvol. Now I have only 
a reproducer outside testsuite:

#/btrfs_test.img /btrfs_mnt_root auto loop,subvol=/ 0 0
#/btrfs_test.img /btrfs_mnt auto loop,subvolid=257 0 0
#/btrfs_mnt_root/d0/dd0/ddd0/s1/bind-mnt /btrfs_bind auto bind 0 0

Round 1:
Uncomment 1st and 3rd line and call mount -a.

Round 2:
Uncomment 2nd line and call mount -a.

Result:
Only two mounts exist.

I am working on a subtest that will trigger it inside the test suite.

I already have a possible fix for it, but I want to confirm that it is 
correct before sending it upstream.

-- 
Best Regards / S pozdravem,

Stanislav Brabec
software developer
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