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: Richard Kennedy <richard@rsk.demon.co.uk> CC: Jan Kara <jack@suse.cz> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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@ -41,8 +41,9 @@ struct wb_writeback_args {
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long nr_pages;
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struct super_block *sb;
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enum writeback_sync_modes sync_mode;
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int for_kupdate;
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int range_cyclic;
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int for_kupdate:1;
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int range_cyclic:1;
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int for_background:1;
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};
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/*
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@ -257,6 +258,15 @@ void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
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.range_cyclic = 1,
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};
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/*
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* We treat @nr_pages=0 as the special case to do background writeback,
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* ie. to sync pages until the background dirty threshold is reached.
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*/
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if (!nr_pages) {
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args.nr_pages = LONG_MAX;
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args.for_background = 1;
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}
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bdi_alloc_queue_work(bdi, &args);
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}
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@ -720,20 +730,16 @@ static long wb_writeback(struct bdi_writeback *wb,
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for (;;) {
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/*
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* Don't flush anything for non-integrity writeback where
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* no nr_pages was given
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* Stop writeback when nr_pages has been consumed
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*/
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if (!args->for_kupdate && args->nr_pages <= 0 &&
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args->sync_mode == WB_SYNC_NONE)
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if (args->nr_pages <= 0)
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break;
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/*
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* If no specific pages were given and this is just a
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* periodic background writeout and we are below the
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* background dirty threshold, don't do anything
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* For background writeout, stop when we are below the
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* background dirty threshold
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*/
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if (args->for_kupdate && args->nr_pages <= 0 &&
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!over_bground_thresh())
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if (args->for_background && !over_bground_thresh())
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break;
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wbc.more_io = 0;
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@ -593,10 +593,10 @@ static void balance_dirty_pages(struct address_space *mapping,
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* background_thresh, to keep the amount of dirty memory low.
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*/
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if ((laptop_mode && pages_written) ||
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(!laptop_mode && ((nr_writeback = global_page_state(NR_FILE_DIRTY)
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+ global_page_state(NR_UNSTABLE_NFS))
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(!laptop_mode && ((global_page_state(NR_FILE_DIRTY)
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+ global_page_state(NR_UNSTABLE_NFS))
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> background_thresh)))
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bdi_start_writeback(bdi, nr_writeback);
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bdi_start_writeback(bdi, 0);
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}
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void set_page_dirty_balance(struct page *page, int page_mkwrite)
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