Commit d3ddec76 authored by Wu Fengguang's avatar Wu Fengguang Committed by Jens Axboe
Browse files

writeback: stop background writeback when below background threshold 



Treat bdi_start_writeback(0) as a special request to do background write,
and stop such work when we are below the background dirty threshold.

Also simplify the (nr_pages <= 0) checks. Since we already pass in
nr_pages=LONG_MAX for WB_SYNC_ALL and background writes, we don't
need to worry about it being decreased to zero.

Reported-by: default avatarRichard Kennedy <richard@rsk.demon.co.uk>
CC: Jan Kara <jack@suse.cz>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 3a2e9a5a

fs/fs-writeback.c

+17 −11
Original line number Diff line number Diff line
@@ -41,8 +41,9 @@ struct wb_writeback_args { 
	long nr_pages;

	struct super_block *sb;

	enum writeback_sync_modes sync_mode;

	int for_kupdate;

	int range_cyclic;

	int for_kupdate:1;

	int range_cyclic:1;

	int for_background:1;

};



/*
@@ -257,6 +258,15 @@ void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages) 
		.range_cyclic	= 1,

	};



	/*

	 * We treat @nr_pages=0 as the special case to do background writeback,

	 * ie. to sync pages until the background dirty threshold is reached.

	 */

	if (!nr_pages) {

		args.nr_pages = LONG_MAX;

		args.for_background = 1;

	}



	bdi_alloc_queue_work(bdi, &args);

}
@@ -720,20 +730,16 @@ static long wb_writeback(struct bdi_writeback *wb, 


	for (;;) {

		/*

		 * Don't flush anything for non-integrity writeback where

		 * no nr_pages was given

		 * Stop writeback when nr_pages has been consumed

		 */

		if (!args->for_kupdate && args->nr_pages <= 0 &&

		     args->sync_mode == WB_SYNC_NONE)

		if (args->nr_pages <= 0)

			break;



		/*

		 * If no specific pages were given and this is just a

		 * periodic background writeout and we are below the

		 * background dirty threshold, don't do anything

		 * For background writeout, stop when we are below the

		 * background dirty threshold

		 */

		if (args->for_kupdate && args->nr_pages <= 0 &&

		    !over_bground_thresh())

		if (args->for_background && !over_bground_thresh())

			break;



		wbc.more_io = 0;

mm/page-writeback.c

+3 −3
Original line number Diff line number Diff line
@@ -593,10 +593,10 @@ static void balance_dirty_pages(struct address_space *mapping, 
	 * background_thresh, to keep the amount of dirty memory low.

	 */

	if ((laptop_mode && pages_written) ||

	    (!laptop_mode && ((nr_writeback = global_page_state(NR_FILE_DIRTY)

	    (!laptop_mode && ((global_page_state(NR_FILE_DIRTY)

			       + global_page_state(NR_UNSTABLE_NFS))

					  > background_thresh)))

		bdi_start_writeback(bdi, nr_writeback);

		bdi_start_writeback(bdi, 0);

}



void set_page_dirty_balance(struct page *page, int page_mkwrite)

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