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Subject: Re: [RFC] Converging userspace and kernel code
To: Goldwyn Rodrigues <rgoldwyn@suse.de>, linux-btrfs@vger.kernel.org,
        Jeff Mahoney <jeffm@suse.com>, David Sterba <dsterba@suse.com>
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From: Anand Jain <anand.jain@oracle.com>
Message-ID: <2dfce804-d1ba-d9e4-e7b3-9c726ff5b49b@oracle.com>
Date: Wed, 11 Jan 2017 10:23:34 +0800
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On 01/11/17 00:04, Goldwyn Rodrigues wrote:
>
>
> On 01/10/2017 09:20 AM, Anand Jain wrote:
>>
>>
>> On 01/10/17 20:14, Goldwyn Rodrigues wrote:
>>>
>>>
>>> On 01/09/2017 09:28 PM, Anand Jain wrote:
>>>>
>>>> Goldwyn,
>>>>
>>>>  Could you add a list what functionality in btrfs-progs will
>>>>  be using the 'core'. ?
>>>
>>>
>>> There are too many to list. It would contain the algorithmic functions
>>> of btrfs which would be able to interact with both kernel and
>>> btrfs-progs.
>>
>>  I am getting confused. How about a few from the btrfs-progs ?
>>
>>
>
> Functions such as open_ctree(), or the set/get functions. The idea is to
> keep the codebase of this core component the same in btrfs-progs and kernel.

  The btrfs-progs open_ctree() is used for the offline functionality
  such as fsck...

> As an example, see how XFS have done using libxfs. Something around the
> same lines.
>

  Does XFS progs access the disks directly (without going through the
  kernel) while kernel has mounted the disk ? If yes, how does it
  maintain the consistency ? Calling sync for the sake of read access
  by the progs, is not a good idea as it causes jitters in the steady
  state IOPS for the applications. I have investigated these concerns
  at the data centers earlier.

Thanks, Anand