3  * mm/page-writeback.c
24 #include <linux/writeback.h>
41 #include <trace/events/writeback.h>
65  * will look to see if it needs to force writeback or throttling.
72  * Start background writeback (via writeback threads) at this percentage
89  * The generator of dirty data starts writeback at this percentage
252  * requiring writeback.
441  * global_dirty_limits - background-writeback and dirty-throttling thresholds
1056 	 * 1% by default. Without strictlimit feature, fuse writeback may  in wb_position_ratio()
1557 	 * time, a small pool of dirty/writeback pages may go empty and disk go  in wb_max_pause()
1688  * If we're over `background_thresh' then the writeback threads are woken to
1740 			unsigned long filepages, headroom, writeback;  in balance_dirty_pages()  local
1747 					    &mdtc->dirty, &writeback);  in balance_dirty_pages()
1748 			mdtc->dirty += writeback;  in balance_dirty_pages()
1779 		 * Throttle it only when the background writeback cannot  in balance_dirty_pages()
1808 		/* Start writeback even when in laptop mode */  in balance_dirty_pages()
2004  * dirty state and will initiate writeback if needed.
2078  * dirty state and will initiate writeback if needed.
2094  * Determines whether background writeback should keep writing @wb or it's
2097  * Return: %true if writeback should continue.
2111 	 * as we're trying to decide whether to put more under writeback.  in wb_over_bg_thresh()
2130 		unsigned long filepages, headroom, writeback;  in wb_over_bg_thresh()  local
2133 				    &writeback);  in wb_over_bg_thresh()
2135 		domain_dirty_limits(mdtc);	/* ditto, ignore writeback */  in wb_over_bg_thresh()
2166 	 * Writing 0 to dirty_writeback_interval will disable periodic writeback  in dirty_writeback_centisecs_handler()
2167 	 * and a different non-zero value will wakeup the writeback threads.  in dirty_writeback_centisecs_handler()
2189  * We've spun up the disk and we're in laptop mode: schedule writeback
2200  * caused another writeback to be scheduled by laptop_io_completion.
2201  * Nothing needs to be written back anymore, so we unschedule the writeback.
2321  * Called early on to tune the page writeback dirty limits.
2340 	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/writeback:online",  in page_writeback_init()
2342 	cpuhp_setup_state(CPUHP_MM_WRITEBACK_DEAD, "mm/writeback:dead", NULL,  in page_writeback_init()
2358  * TOWRITE tag to identify pages eligible for writeback.  This mechanism is
2359  * used to avoid livelocking of writeback by a process steadily creating new
2393  * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
2407  * To avoid deadlocks between range_cyclic writeback and callers that hold
2410  * lock/page writeback access order inversion - we should only ever lock
2501 				 * writeback. There's no need to continue for  in write_cache_pages()
2502 				 * background writeback. Just push done_index  in write_cache_pages()
2505 				 * writeback, we must process the entire dirty  in write_cache_pages()
2528 			 * we tagged for writeback prior to entering this loop.  in write_cache_pages()
2591 		 * Lacking an allocation context or the locality or writeback  in do_writepages()
2593 		 * writeback activity on the local node. It's as good a  in do_writepages()
2601 	 * but if there's constant writeback being submitted, this makes sure  in do_writepages()
2602 	 * writeback bandwidth is updated once in a while.  in do_writepages()
2656  * Helper function for deaccounting dirty page without writeback.
2738  * @wbc: The writeback control.
2902 		 *      cause the writeback.  in folio_clear_dirty_for_io()
2953 	 * Make sure estimate of writeback throughput gets updated after  in wb_inode_writeback_end()
2954 	 * writeback completed. We delay the update by BANDWIDTH_INTERVAL  in wb_inode_writeback_end()
2956 	 * that if multiple inodes end writeback at a similar time, they get  in wb_inode_writeback_end()
3065 	 * If writeback has been triggered on a page that cannot be made  in __folio_start_writeback()
3075  * folio_wait_writeback - Wait for a folio to finish writeback.
3083  * If the folio is not locked, writeback may start again after writeback
3096  * folio_wait_writeback_killable - Wait for a folio to finish writeback.
3104  * If the folio is not locked, writeback may start again after writeback
3121  * folio_wait_stable() - wait for writeback to finish, if necessary.
3125  * device that requires folio contents to be held stable during writeback.
3126  * If so, then it will wait for any pending writeback to complete.
3130  * If the folio is not locked, writeback may start again after writeback