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Re: [PATCH 10/12] writeback: only allow one inflight and pending full flush

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On Fri, Sep 29, 2017 at 3:17 AM, Jens Axboe <axboe@kernel.dk> wrote:
> On 09/28/2017 11:44 PM, Linus Torvalds wrote:
>> On Thu, Sep 28, 2017 at 2:41 PM, Andrew Morton
>> <akpm@linux-foundation.org> wrote:
>>>
>>> test_and_set_bit()?
>>
>> If there aren't any atomicity concerns (either because of higher-level
>> locking, or because racing and having two people set the bit is fine),
>> it can be better to do them separately if the test_bit() is the common
>> case and you can avoid dirtying a cacheline that way.
>>
>> But yeah, if that is the case, it might be worth documenting, because
>> test_and_set_bit() is the more obviously appropriate "there can be
>> only one" model.
>
> It is documented though, but maybe not well enough...
>
> I've actually had to document/explain it enough times now, that it
> might be worth making a general construct. Though it has to be
> used carefully, so perhaps it's better contained as separate use
> cases.
>

Maybe change "Ensure that we only allow one of them pending"
in the comment above. Only the "allow one inflight" part is correct.

Or apply your follow up patch and be done with in...

Amir.

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[PATCH 0/12 v3] Writeback improvements Jens Axboe <axboe@kernel.dk> - 2017-09-27 22:20 +0200
  [PATCH 10/12] writeback: only allow one inflight and pending full flush Jens Axboe <axboe@kernel.dk> - 2017-09-27 22:20 +0200
    Re: [PATCH 10/12] writeback: only allow one inflight and pending  full flush Andrew Morton <akpm@linux-foundation.org> - 2017-09-28 23:50 +0200
      Re: [PATCH 10/12] writeback: only allow one inflight and pending full flush Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-28 23:50 +0200
        Re: [PATCH 10/12] writeback: only allow one inflight and pending full  flush Jens Axboe <axboe@kernel.dk> - 2017-09-29 02:20 +0200
          Re: [PATCH 10/12] writeback: only allow one inflight and pending full flush Amir Goldstein <amir73il@gmail.com> - 2017-09-29 07:30 +0200
      Re: [PATCH 10/12] writeback: only allow one inflight and pending full  flush Jens Axboe <axboe@kernel.dk> - 2017-09-29 02:20 +0200
  [PATCH 04/12] fs: kill 'nr_pages' argument from wakeup_flusher_threads() Jens Axboe <axboe@kernel.dk> - 2017-09-27 22:20 +0200
  [PATCH 09/12] writeback: move nr_pages == 0 logic to one location Jens Axboe <axboe@kernel.dk> - 2017-09-27 22:20 +0200
  [PATCH 01/12] buffer: have alloc_page_buffers() use __GFP_NOFAIL Jens Axboe <axboe@kernel.dk> - 2017-09-27 22:20 +0200
    Re: [PATCH 01/12] buffer: have alloc_page_buffers() use __GFP_NOFAIL Nikolay Borisov <nborisov@suse.com> - 2017-09-28 17:30 +0200
  [PATCH 03/12] buffer: eliminate the need to call free_more_memory() in __getblk_slow() Jens Axboe <axboe@kernel.dk> - 2017-09-27 22:20 +0200
    Re: [PATCH 03/12] buffer: eliminate the need to call  free_more_memory() in __getblk_slow() Nikolay Borisov <nborisov@suse.com> - 2017-09-28 17:40 +0200
  [PATCH 06/12] writeback: provide a wakeup_flusher_threads_bdi() Jens Axboe <axboe@kernel.dk> - 2017-09-27 22:20 +0200
  [PATCH 05/12] writeback: switch wakeup_flusher_threads() to cyclic writeback Jens Axboe <axboe@kernel.dk> - 2017-09-27 22:20 +0200
  [PATCH 11/12] writeback: make sync_inodes_sb() use range cyclic writeback Jens Axboe <axboe@kernel.dk> - 2017-09-27 22:20 +0200
  [PATCH 07/12] writeback: pass in '0' for nr_pages writeback in laptop mode Jens Axboe <axboe@kernel.dk> - 2017-09-27 22:20 +0200
  Re: [PATCH 0/12 v3] Writeback improvements John Stoffel <john@quad.stoffel.home> - 2017-09-28 15:20 +0200
    Re: [PATCH 0/12 v3] Writeback improvements Jens Axboe <axboe@kernel.dk> - 2017-09-28 15:50 +0200

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