Re: [PATCH 1/1] nilfs2: add mount option that reduces super block writes

[Andreas Rohner <andreas.rohner-hi6Y0CQ0nG0@public.gmane.org>]

Hi Vyacheslav,

On 2014-01-30 07:36, Vyacheslav Dubeyko wrote:
> Hi Andreas,
> 
> On Jan 30, 2014, at 5:47 AM, Andreas Rohner wrote:
> 
>> This patch introduces a mount option bad_ftl that disables the
>> periodic overwrites of the super block to make the file system better
>> suitable for bad flash memory with a bad FTL. The super block is only
>> written at umount time. So if there is a power outage the file system
>> needs to be recovered by a linear scan of all segment summary blocks.
>>
>> The linear scan is only necessary if the file system wasn't umounted
>> properly. So the normal mount time is not affected.
>>
>> Signed-off-by: Andreas Rohner <andreas.rohner-hi6Y0CQ0nG0@public.gmane.org>
>> ---
>> fs/nilfs2/segbuf.c        |  3 ++-
>> fs/nilfs2/segment.c       |  3 ++-
>> fs/nilfs2/super.c         | 10 +++++++--
>> fs/nilfs2/the_nilfs.c     | 54 ++++++++++++++++++++++++++++++++++++++++++++---
>> include/linux/nilfs2_fs.h |  4 +++-
>> 5 files changed, 66 insertions(+), 8 deletions(-)
>>
> 
> As far as I can judge, conceptually it is simply rollback of the fix [1].

The normal recovery mode checks all partial segments and computes the
checksum over all the data. That takes significantly longer than my
approach of just checking one block per segment, namely the segment
summary block.

br,
Andreas Rohner

> Thanks,
> Vyacheslav Dubeyko.
> 
> [1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a9bae189542e71f91e61a4428adf6e5a7dfe8063
> 
> 

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