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
254  * requiring writeback.
443  * global_dirty_limits - background-writeback and dirty-throttling thresholds
871  * decide whether to put more under writeback.
882 		unsigned long filepages = 0, headroom = 0, writeback = 0;  in domain_dirty_avail()  local
885 				    &writeback);  in domain_dirty_avail()
887 			dtc->dirty += writeback;  in domain_dirty_avail()
1101 	 * 1% by default. Without strictlimit feature, fuse writeback may  in wb_position_ratio()
1602 	 * time, a small pool of dirty/writeback pages may go empty and disk go  in wb_max_pause()
1746  * Throttle it only when the background writeback cannot catch-up. This avoids
1827  * If we're over `background_thresh' then the writeback threads are woken to
1899 		/* Start writeback even when in laptop mode */  in balance_dirty_pages()
2064  * dirty state and will initiate writeback if needed.
2138  * dirty state and will initiate writeback if needed.
2152  * and thresh, but it's for background writeback.
2183  * Determines whether background writeback should keep writing @wb or it's
2186  * Return: %true if writeback should continue.
2215 	 * Writing 0 to dirty_writeback_interval will disable periodic writeback  in dirty_writeback_centisecs_handler()
2216 	 * and a different non-zero value will wakeup the writeback threads.  in dirty_writeback_centisecs_handler()
2238  * We've spun up the disk and we're in laptop mode: schedule writeback
2249  * caused another writeback to be scheduled by laptop_io_completion.
2250  * Nothing needs to be written back anymore, so we unschedule the writeback.
2369  * Called early on to tune the page writeback dirty limits.
2388 	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/writeback:online",  in page_writeback_init()
2390 	cpuhp_setup_state(CPUHP_MM_WRITEBACK_DEAD, "mm/writeback:dead", NULL,  in page_writeback_init()
2398  * tag_pages_for_writeback - tag pages to be written by writeback
2405  * can then use the TOWRITE tag to identify pages eligible for writeback.
2406  * This mechanism is used to avoid livelocking of writeback by a process
2507  * writeback_iter - iterate folio of a mapping for writeback
2509  * @wbc: writeback context
2511  * @error: in-out pointer for writeback errors (see below)
2513  * This function returns the next folio for the writeback operation described by
2517  * To start the writeback operation, %NULL is passed in the @folio argument, and
2521  * If there was an error in the per-folio writeback inside the writeback_iter()
2524  * Once the writeback described in @wbc has finished, this function will return
2540 		 * For range cyclic writeback we remember where we stopped so  in writeback_iter()
2543 		 * For non-cyclic writeback we always start at the beginning of  in writeback_iter()
2556 		 * For data-integrity writeback we have to be careful so that we  in writeback_iter()
2571 		 * For integrity writeback we have to keep going until we have  in writeback_iter()
2572 		 * written all the folios we tagged for writeback above, even if  in writeback_iter()
2578 		 * For background writeback we exit as soon as we run past  in writeback_iter()
2593 		 * To avoid deadlocks between range_cyclic writeback and callers  in writeback_iter()
2595 		 * the writeback iteration finishes, we do not loop back to the  in writeback_iter()
2597 		 * writeback access order inversion - we should only ever lock  in writeback_iter()
2694 		 * Lacking an allocation context or the locality or writeback  in do_writepages()
2696 		 * writeback activity on the local node. It's as good a  in do_writepages()
2704 	 * but if there's constant writeback being submitted, this makes sure  in do_writepages()
2705 	 * writeback bandwidth is updated once in a while.  in do_writepages()
2759  * Helper function for deaccounting dirty page without writeback.
2844  * @wbc: The writeback control.
3008 		 *      cause the writeback.  in folio_clear_dirty_for_io()
3059 	 * Make sure estimate of writeback throughput gets updated after  in wb_inode_writeback_end()
3060 	 * writeback completed. We delay the update by BANDWIDTH_INTERVAL  in wb_inode_writeback_end()
3062 	 * that if multiple inodes end writeback at a similar time, they get  in wb_inode_writeback_end()
3166 	 * If writeback has been triggered on a page that cannot be made  in __folio_start_writeback()
3174  * folio_wait_writeback - Wait for a folio to finish writeback.
3182  * If the folio is not locked, writeback may start again after writeback
3195  * folio_wait_writeback_killable - Wait for a folio to finish writeback.
3203  * If the folio is not locked, writeback may start again after writeback
3220  * folio_wait_stable() - wait for writeback to finish, if necessary.
3224  * device that requires folio contents to be held stable during writeback.
3225  * If so, then it will wait for any pending writeback to complete.
3229  * If the folio is not locked, writeback may start again after writeback