Re: [PATCH] Snapshot/subvolume listing feature

[TARUISI Hiroaki <taruishi.hiroak@jp.fujitsu.com>]

Thank you for your advice.

I'm aware of redundant search, but I didn't think of
getdents like interface.

I'll remake it without redundant search.

Regards,
taruisi

Yan, Zheng wrote:
> 2009/11/16 TARUISI Hiroaki <taruishi.hiroak@jp.fujitsu.com>:
>> I made Snapshot/subvolume listing feature.
>>
>> This feature consists of two patches, for kernel(ioctl),
>> and for progs(btrfsctl). I send these two patches as response
>> of this mail soon.
>>
>> New option '-l' is introduced to btrfsctl for listing.
>>
>> If this option is specified, btrfsctl call new ioctl. New ioctl
>> searches root tree and enumerates subtrees. For each subtrees,
>> ioctl searches directory path to tree root, and enumerates
>> more descendant until no more subtree is found.
>>
>> MANPAGE-like option description and examples are as follows.
>>
>>  OPTIONS
>>        -l _file_
>>                List all snapshot/subvolume directories under a tree
>>                which _file_ belongs to.
>>
>>  EXAMPLES
>>        # btrfsctl -l /work/btrfs
>>    Base path = /work/btrfs/
>>    No.    Tree ID      Subvolume Relative Path
>>     1         256      ss1/
>>     2         257      ss2/
>>     3         258      svs1/ss1/
>>     4         259      svs1/ss2/
>>     5         260      svs2/ss1/
>>     6         261      svs2/ss2/
>>     7         262      ss3/
>>     8         263      ss4/
>>     9         264      sv_pool/
>>    10         265      sv_pool/ss01/
>>    11         266      sv_pool/ss02/
>>    12         267      sv_pool/ss03/
>>    13         268      sv_pool/ss04/
>>    14         269      sv_pool/ss05/
>>    15         270      sv_pool/ss06/
>>    16         271      sv_pool/ss07/
>>    17         272      sv_pool/ss08/
>>    18         273      sv_pool/ss09/
>>    19         274      sv_pool/ss10/
>>  operation complete
>>  Btrfs v0.19-9-gd67dad2
>>
> 
> Thank you for doing this.
> 
> I have a quick look at the patches. It seems the ioctl returns full path
> to each subvolume and uses sequence ID to indicate the progress
> of listing. Every time the ioctl is called, it tries building full list of
> subvolume, then skip entries that already returned.  I think the API is
> suboptimal, a getdents like API is better. (The ioctl only lists subvolumes
> within a given subvolume, the user program call the ioctl recursively
> to list all subvolumes.)
> 
> Yan, Zheng
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