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 disappear !
Patches will follow shortly
>
> # 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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