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
>
>>
>> # 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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