Messages in this thread | | | Subject | Re: [PATCH 2/6] writeback: wb_start_writeback() should use WB_SYNC_ALL for WB_REASON_SYNC | From | Jens Axboe <> | Date | Tue, 22 Mar 2016 15:40:28 -0600 |
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On 03/22/2016 03:34 PM, Dave Chinner wrote: > 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.
It's not going to block. wakeup_flusher_threads() async queues writeback work through wb_start_writeback().
> 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.
That's fine, they can get to wait on the previously issued IO, which was properly submitted with WB_SYNC_ALL.
Maybe I'm missing your point?
-- Jens Axboe
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