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 15:51:01 -0600 |
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On 03/22/2016 03:40 PM, Jens Axboe wrote: > 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().
For block here, you mean the async work ending up doing wait_on_page_writeback() because we're doing WB_SYNC_ALL instead of WB_SYNC_NONE?
And if so:
>> 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.
why not have it do that?
-- Jens Axboe
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