Re: [PATCH 1/3] btrfs-progs: random fixes of btrfs-filesystem documentation

[Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>]

Hi Eric,

(2014/08/12 2:14), Eric Sandeen wrote:
> On 8/11/14, 10:05 AM, Eric Sandeen wrote:
>> On 8/11/14, 2:11 AM, Satoru Takeuchi wrote:
>>> From: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
>>>
>>>   - Simplify and unify the description of both man and usage.
>>>   - Fix to show -m and -d is not exclusive
>>>     with "<path>|<uuid>|<device>|<label>".
>>>   - Add the description about short options for "--mounted" and
>>>     "--all-devices", "-m" and "-d" respectively.
>>>   - Move the descriptions of options to "Options" section.
>>>
>>> Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
>>>
>>> ---
>>>   Documentation/btrfs-filesystem.txt | 22 ++++++++++++++--------
>>>   cmds-filesystem.c                  | 15 ++++++++++-----
>>>   2 files changed, 24 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/Documentation/btrfs-filesystem.txt b/Documentation/btrfs-filesystem.txt
>>> index c9c0b00..fe68496 100644
>>> --- a/Documentation/btrfs-filesystem.txt
>>> +++ b/Documentation/btrfs-filesystem.txt
>>> @@ -20,15 +20,21 @@ SUBCOMMAND
>>>   *df* <path> [<path>...]::
>>>   Show space usage information for a mount point.
>>>   
>>> -*show* [--mounted|--all-devices|<path>|<uuid>|<device>|<label>]::
>>> -Show the btrfs filesystem with some additional info.
>>> +*show* [-d|-m] [<path>|<uuid>|<device>|<label>]::
>>> +Show the structure of btrfs filesystem(s).
>>>   +
>>> -If no option nor <path>|<uuid>|<device>|<label> is passed, btrfs shows
>>> -information of all the btrfs filesystem both mounted and unmounted.
>>> -If '--mounted' is passed, it would probe btrfs kernel to list mounted btrfs
>>> -filesystem(s);
>>> -If '--all-devices' is passed, all the devices under /dev are scanned;
>>> -otherwise the devices list is extracted from the /proc/partitions file.
>>
>>> +If none of '<path>|<uuid>|<device>|<label>' is passed, btrfs shows
>>> +information of all the btrfs filesystems both mounted and unmounted.
>>
>> that doesn't seem quite correct;
>>
>> # btrfs filesystem show -m
>>
>> does not specify '<path>|<uuid>|<device>|<label>' but it only shows
>> mounted filesystems, not all filesystems.
>>
>> As I understand it, the -d and -m options control how the command
>> finds devices; the '<path>|<uuid>|<device>|<label>' argument is
>> used as a filter for what is found.
>>
>>> ++
>>> +The show command finds btrfs filesystems by scanning all the devices
>>> +in /proc/partitions by default.
>>
>> I think I would document it something like this:
>>
>> show [-m|-d] [<path>|<uuid>|<device>|<label>]
>> 	Show the structure of btrfs filesystem(s).
>>
>> 	By default, the show command scans all devices found in /proc/partitions.	
>> 	If [-d|--all-devices] is specified, all devices found under /dev are scanned.
>> 	If [-m|--mounted] is specified, only mounted (btrfs?) devices are scanned.
>>
>> 	By default, the structure of all discovered filesystems is shown.
>> 	If any one of [<path>|<uuid>|<device>|<label>] is specified, only filesystems
>> 	matching that identifier are shown.
>>
>> (What seems to be missing, though, is why would the user ever choose to use '-d?')
> 
> Incidentally, there is some strange behavior here when looking for multiple filesystems which match.
> 
> Make 2 filesystems w/ the same label:
> 
> [root@bp-05 tmp]# btrfs filesystem label /dev/sdc1 testlabel2
> [root@bp-05 tmp]# btrfs filesystem label /dev/sdc5 testlabel2
> 
> Show matching filesytems:
> 
> [root@bp-05 tmp]# btrfs filesystem show testlabel2
> Label: 'testlabel2'  uuid: 8c6ec835-5628-439b-9749-d92f62573ce8
> 	Total devices 1 FS bytes used 112.00KiB
> 	devid    1 size 30.00GiB used 2.04GiB path /dev/sdc5
> 
> Label: 'testlabel2'  uuid: a43cd507-02a2-46d2-a754-322cb7bdc346
> 	Total devices 1 FS bytes used 384.00KiB
> 	devid    1 size 30.00GiB used 2.04GiB path /dev/sdc1
> 
> Btrfs v3.14.2
> 
> That works fine, but if one is mounted:
> 
> [root@bp-05 tmp]# mount /dev/sdc1 /mnt/test
> 
> only the mounted filesystem is shown:
> 
> [root@bp-05 tmp]# btrfs filesystem show testlabel2
> Label: 'testlabel2'  uuid: a43cd507-02a2-46d2-a754-322cb7bdc346
> 	Total devices 1 FS bytes used 384.00KiB
> 	devid    1 size 30.00GiB used 2.04GiB path /dev/sdc1
> 
> Btrfs v3.14.2
> 
> That's unexpected.
> 
> Mount the other fs, and both are shown again:
> 
> [root@bp-05 tmp]# mount /dev/sdc5 /mnt/scratch
> [root@bp-05 tmp]# btrfs filesystem show testlabel2
> Label: 'testlabel2'  uuid: a43cd507-02a2-46d2-a754-322cb7bdc346
> 	Total devices 1 FS bytes used 384.00KiB
> 	devid    1 size 30.00GiB used 2.04GiB path /dev/sdc1
> 
> Label: 'testlabel2'  uuid: 8c6ec835-5628-439b-9749-d92f62573ce8
> 	Total devices 1 FS bytes used 384.00KiB
> 	devid    1 size 30.00GiB used 2.04GiB path /dev/sdc5
> 
> Btrfs v3.14.2

I'll dig into it. Thank you for let me know.

Satoru

> 
> 
> -Eric
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