Re: [PATCH v2 07/25] pnfsblock: add blocklayout Kconfig option, Makefile, and stubs

From: Benny Halevy <bhalevy@tonian.com>
To: "Myklebust, Trond" <Trond.Myklebust@netapp.com>
Cc: Jim Rees <rees@umich.edu>,
	linux-nfs@vger.kernel.org, peter honeyman <honey@citi.umich.edu>
Subject: Re: [PATCH v2 07/25] pnfsblock: add blocklayout Kconfig option, Makefile, and stubs
Date: Mon, 25 Jul 2011 14:26:50 -0400	[thread overview]
Message-ID: <4E2DB56A.9010908@tonian.com> (raw)
In-Reply-To: <2E1EB2CF9ED1CB4AA966F0EB76EAB4430A517C9D@SACMVEXC2-PRD.hq.netapp.com>

On 2011-07-25 13:25, Myklebust, Trond wrote:
>> -----Original Message-----
>> From: Benny Halevy [mailto:bhalevy@tonian.com]
>> Sent: Monday, July 25, 2011 10:50 AM
>> To: Myklebust, Trond
>> Cc: Jim Rees; linux-nfs@vger.kernel.org; peter honeyman
>> Subject: Re: [PATCH v2 07/25] pnfsblock: add blocklayout Kconfig
>> option, Makefile, and stubs
>>
>> On 2011-07-25 10:38, Myklebust, Trond wrote:
>>>> -----Original Message-----
>>>> From: Benny Halevy [mailto:bhalevy@tonian.com]
>>>> Sent: Monday, July 25, 2011 10:31 AM
>>>> To: Jim Rees
>>>> Cc: Myklebust, Trond; linux-nfs@vger.kernel.org; peter honeyman
>>>> Subject: Re: [PATCH v2 07/25] pnfsblock: add blocklayout Kconfig
>>>> option, Makefile, and stubs
>>>>
>>>> On 2011-07-21 15:34, Jim Rees wrote:
>>>>> From: Fred Isaman <iisaman@citi.umich.edu>
>>>>>
>>>>> Define a configuration variable to enable/disable compilation of
>> the
>>>>> block driver code.
>>>>>
>>>>> Add the minimal structure for a pnfs block layout driver, and
> empty
>>>>> list-heads that will hold the extent data
>>>>>
>>>>> [pnfsblock: make NFS_V4_1 select PNFS_BLOCK]
>>>>> Signed-off-by: Peng Tao <peng_tao@emc.com>
>>>>> Signed-off-by: Fred Isaman <iisaman@citi.umich.edu>
>>>>> Signed-off-by: Benny Halevy <bhalevy@panasas.com>
>>>>> [pnfs-block: fix CONFIG_PNFS_BLOCK dependencies]
>>>>> Signed-off-by: Benny Halevy <bhalevy@panasas.com>
>>>>> Signed-off-by: Benny Halevy <benny@tonian.com>
>>>>> [pnfsblock: SQUASHME: port block layout code]
>>>>> Signed-off-by: Peng Tao <peng_tao@emc.com>
>>>>> [pnfsblock: SQUASHME: adjust to API change]
>>>>> Signed-off-by: Fred Isaman <iisaman@citi.umich.edu>
>>>>> [pnfs: move pnfs_layout_type inline in nfs_inode]
>>>>> Signed-off-by: Benny Halevy <bhalevy@panasas.com>
>>>>> [blocklayout: encode_layoutcommit implementation]
>>>>> Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
>>>>> Signed-off-by: Benny Halevy <bhalevy@panasas.com>
>>>>> Signed-off-by: Benny Halevy <benny@tonian.com>
>>>>> [pnfsblock: layout alloc and free]
>>>>> Signed-off-by: Fred Isaman <iisaman@citi.umich.edu>
>>>>> [pnfs: move pnfs_layout_type inline in nfs_inode]
>>>>> Signed-off-by: Benny Halevy <bhalevy@panasas.com>
>>>>> Signed-off-by: Benny Halevy <benny@tonian.com>
>>>>> [pnfsblock: define module alias]
>>>>> Signed-off-by: Peng Tao <peng_tao@emc.com>
>>>>> ---
>>>>>  fs/nfs/Kconfig                   |    8 ++-
>>>>>  fs/nfs/Makefile                  |    1 +
>>>>>  fs/nfs/blocklayout/Makefile      |    5 +
>>>>>  fs/nfs/blocklayout/blocklayout.c |  175
>>>> ++++++++++++++++++++++++++++++++++++++
>>>>>  fs/nfs/blocklayout/blocklayout.h |   91 ++++++++++++++++++++
>>>>>  5 files changed, 279 insertions(+), 1 deletions(-)
>>>>>  create mode 100644 fs/nfs/blocklayout/Makefile
>>>>>  create mode 100644 fs/nfs/blocklayout/blocklayout.c
>>>>>  create mode 100644 fs/nfs/blocklayout/blocklayout.h
>>>>>
>>>>> diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
>>>>> index 2cde5d9..be02077 100644
>>>>> --- a/fs/nfs/Kconfig
>>>>> +++ b/fs/nfs/Kconfig
>>>>> @@ -79,15 +79,21 @@ config NFS_V4_1
>>>>>  	depends on NFS_FS && NFS_V4 && EXPERIMENTAL
>>>>>  	select SUNRPC_BACKCHANNEL
>>>>>  	select PNFS_FILE_LAYOUT
>>>>> +	select PNFS_BLOCK
>>>>> +	select MD
>>>>> +	select BLK_DEV_DM
>>>>
>>>> Why is PNFS_BLOCK enabled automatically in all cases?
>>>> That renders the use of modules for layout drivers totally useless.
>>>> I sort of understand that for PNFS_FILE_LAYOUT (when my
>>>> arm is twisted really hard behind my back :) since it
>>>> is an integral part of RFC5661 but what's the justification
>>>> for PNFS_BLOCK? and why blocks and not objects?
>>>
>>> The question is rather why did objects add a selectable compile
>> option?
>>
>> Just good citizenship :)
>>
>>> What is the point of not compiling a given layout driver if all the
>>> dependencies are met?
>>
>> Reducing build times...
>> Building a smaller kernel when modules are disabled...
> 
> 
> You can add a line with
> 	depends on m
> 
> to ensure that it is always compiled as a module. I think that might be
> a good thing until we have nailed down all the issues with pNFS.
> 

I'd rather leave it as is so it's easier to test without CONFIG_MODULES.

>> We're fine in terms of memory consumption when CONFIG_MODULES=y since
>> the
>> layout driver is loaded on demand but shouldn't be worried about
>> the other case?
>>
>>>
>>> IOW: The only thing I'd change above is the select MD and select
>>> BLK_DEV_DM: I'd prefer something like
>>>
>>> config PNFS_BLOCK
>>> 	depends on NFS_V4_1 && MD && BLK_DEV_DM
>>> 	default y
>>
>> This is closer to the original version.
>> However, selecting MD and BLK_DEV_DM was proven useful to
> automatically
>> take
>> care of the module dependencies without having to dive into details.
> 
> Yes, but since the MD is a completely different layer that is not under
> our control (well, OK, Neil is still an NFS maintainer and an MD
> maintainer) then I'd prefer to leave it as a dependency.
> 
> We can always add something like
> 
> comment
> 	depends on NFS_V4_1 && !BLK_DEV_DM
> 	Please enable BLK_DEV_MD if you wish to enable the pNFS block
> driver.

I never new you can enable comments conditionally this way...
It looks ok to me, I'll try it out and see how it shows in make *config

Benny

> 
> 
> Cheers
>   Trond
> --
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