Re: btrfs fi du -s gives Inappropriate ioctl for device

[Nikolay Borisov <nborisov@suse.com>]

On 18.08.2017 10:09, Goffredo Baroncelli wrote:
> On 08/18/2017 08:34 AM, Nikolay Borisov wrote:
>>
>>
>> On 17.08.2017 23:59, Goffredo Baroncelli wrote:
>>> Hi,
>>>
>>> On 08/17/2017 08:43 PM, Chris Murphy wrote:
>>>> # btrfs sub create test1
>>>> Create subvolume './test1'
>>>> # btrfs sub create test1/test2
>>>> Create subvolume 'test1/test2'
>>>> # btrfs sub snap test1 test1.snap
>>>> Create a snapshot of 'test1' in './test1.snap'
>>>> # btrfs fi du -s test1
>>>>      Total   Exclusive  Set shared  Filename
>>>>      0.00B       0.00B       0.00B  test1
>>>> # btrfs fi du -s test1.snap
>>>>      Total   Exclusive  Set shared  Filename
>>>> ERROR: cannot check space of 'test1.snap': Inappropriate ioctl for device
>>>> #
>>>>
>>>
>>> tanks for the test case. Now I was able to reproduce the problem. The bug(s) are two:
>>>
>>> 1) to get the treeid of the files/directory, the function lookup_path_rootid() is used, which behaves strangely when it is called on a directory that is BTRFS_EMPTY_SUBVOL_DIR_OBJECTID. In fact this function is commented as following:
>>> [....]
>>> /*
>>>  * For a given:
>>>  * - file or directory return the containing tree root id
>>>  * - subvolume return its own tree id
>>>  * - BTRFS_EMPTY_SUBVOL_DIR_OBJECTID (directory with ino == 2) the result is
>>>  *   undefined and function returns -1
>>>  */
>>> int lookup_path_rootid(int fd, u64 *rootid)
>>> {
>>> [....]
>>>
>>> The caller (du_add_file()) doesn't consider this case.
>>>
>>> 2) in the function du_walk_dir(), an error returned by du_add_file() is ignored, but the return value is not reset. So if the last entry has ino BTRFS_EMPTY_SUBVOL_DIR_OBJECTID (directory with ino == 2) an error is returned. But if there is another directory item no error is returned !
>>>
>>> See the following tests cases:
>>>
>>> # btrfs sub create test1
>>> # btrfs sub create test1/test2
>>> # btrfs sub snap test1 test1.snap
>>> # btrfs fi du -s test1
>>>      Total   Exclusive  Set shared  Filename
>>>      0.00B       0.00B       0.00B  test1
>>> # btrfs fi du -s test1.snap
>>>      Total   Exclusive  Set shared  Filename
>>> ERROR: cannot check space of 'test1.snap': Inappropriate ioctl for device
>>>
>>> But if you add *another* file/dir in test1.snap you got:
>>>
>>> # mkdir test1.snap/dir
>>> # btrfs fi du -s test1.snap
>>>      Total   Exclusive  Set shared  Filename
>>>      0.00B       0.00B       0.00B  test1.snap
>>>
>>> The error disappea> Patches will follow shortly
>>
>> It would be awesome if you manage to introduce xfstests for this case
> 
> I am not sure if this is the right thing to do: the bugs are related to 
> a) an incorrect error handling of the function lookup_path_rootid()
> b) the strange behavior of the BTRFS_EMPTY_SUBVOL_DIR_OBJECTID directory
> 
> For a) it is impossible to check for each lookup_path_rootid() call from a xfstest; for b) I am quite sure that there are a lot of corner case not properly handled in btrfs progs (and still btrfs fi-du handle it wrongly)

So the bug is actually in the btrfsprogs not in the fs, am I correct?

> 
> BR
> G.Baroncelli
> 
>>
>>>
>>>>
>>>> # uname -r
>>>> 4.13.0-0.rc4.git1.1.fc27.x86_64
>>>> # rpm -q btrfs-progs
>>>> btrfs-progs-4.12-1.fc27.x86_64
>>>>
>>>>
>>>> ----
>>>> Chris Murphy
>>>>
>>>
>>>
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> 
>