lkml.org 
[lkml]   [2012]   [Sep]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] Fix queueing work if !bdi_cap_writeback_dirty()
Date
Jan Kara <jack@suse.cz> writes:

>> I think you know how to solve it though. You can add the periodic flush
>> in own task. And you can check bdi->dirty_exceeded in any handlers.
> Sure, you can have your private thread. That is possible but you will
> have to duplicate flusher logic and you will still get odd behavior e.g.
> when your filesystem is on one partition and another filesystem is on a
> different partition of the same disk.

Right. But it is what current FSes are doing more or less.

>> Well, ok. The alternative plan but more bigger change is to add the
>> handler to writeback task path. This would be better way, and core
>> should be able to request to flush with usual way (I guess this is what
>> you are concerning). And I believe some FS can implement the simpler
>> and more efficient writeback path.
>>
>> But this would look like what reiserfs4 was submitted in past (before
>> bdi was introduced), and unfortunately never accepted though.
>>
>> Since situation was changed, will we accept it?
>>
>> OK, why my FS requires it? Because basic strategy try to keep the
>> consistency of user view, not only internal metadata consistency.
>> I.e. it works like to flush the snapshot of user view.
>>
>> So, flushing metadata/data by arbitrary order like current writeback
>> task does is unacceptable (of course, except request by user). And
>> writeback task will never know the correct order of FS.
> OK, thanks for explanation. Now I understand what you are trying to do.
> Would it be enough if you could track dirty inodes inside your filesystem
> and provide some callback for flusher so that you can queue these inodes in
> the IO queue?

Yes, I guess so. I'm not doing the experiment this plan yet, so I'm not
sure though. If we provide the callback something like
->writeback_sb_inodes(), it would work.

And the better design is to remove duplication of dirty inode tracking
on writeback task and own FS though. (However, this is quite optional)

Thanks.
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>


\
 
 \ /
  Last update: 2012-09-17 12:21    [W:0.096 / U:0.444 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site