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Re: [PATCH 2/6] writeback: wb_start_writeback() should use WB_SYNC_ALL for WB_REASON_SYNC

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On Tue, Mar 22, 2016 at 11:55:16AM -0600, Jens Axboe wrote:
> If you call sync, the initial call to wakeup_flusher_threads() ends up
> calling wb_start_writeback() with reason=WB_REASON_SYNC, but
> wb_start_writeback() always uses WB_SYNC_NONE as the writeback mode.
> Ensure that we use WB_SYNC_ALL for a sync operation.

This seems wrong to me. We want background write to happen as
quickly as possible and /not block/ when we first kick sync.

The latter blocking passes of sync use WB_SYNC_ALL to ensure that we
block waiting for all remaining IO to be issued and waited on, but
the background writeback doesn't need to do this.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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[PATCH 2/6] writeback: wb_start_writeback() should use WB_SYNC_ALL for WB_REASON_SYNC Jens Axboe <axboe@fb.com> - 2016-03-22 19:00 +0100
  Re: [PATCH 2/6] writeback: wb_start_writeback() should use  WB_SYNC_ALL for WB_REASON_SYNC Dave Chinner <david@fromorbit.com> - 2016-03-22 22:40 +0100
    Re: [PATCH 2/6] writeback: wb_start_writeback() should use  WB_SYNC_ALL for WB_REASON_SYNC Jens Axboe <axboe@fb.com> - 2016-03-22 22:50 +0100
      Re: [PATCH 2/6] writeback: wb_start_writeback() should use  WB_SYNC_ALL for WB_REASON_SYNC Jens Axboe <axboe@fb.com> - 2016-03-22 23:00 +0100
      Re: [PATCH 2/6] writeback: wb_start_writeback() should use  WB_SYNC_ALL for WB_REASON_SYNC Dave Chinner <david@fromorbit.com> - 2016-03-22 23:10 +0100
        Re: [PATCH 2/6] writeback: wb_start_writeback() should use  WB_SYNC_ALL for WB_REASON_SYNC Jens Axboe <axboe@fb.com> - 2016-03-22 23:10 +0100

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