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
231  * requiring writeback.
420  * global_dirty_limits - background-writeback and dirty-throttling thresholds
854  * decide whether to put more under writeback.
865 		unsigned long filepages = 0, headroom = 0, writeback = 0;  in domain_dirty_avail()  local
868 				    &writeback);  in domain_dirty_avail()
870 			dtc->dirty += writeback;  in domain_dirty_avail()
1103 	 * 1% by default. Without strictlimit feature, fuse writeback may  in wb_position_ratio()
1583 	 * time, a small pool of dirty/writeback pages may go empty and disk go  in wb_max_pause()
1727  * Throttle it only when the background writeback cannot catch-up. This avoids
1808  * If we're over `background_thresh' then the writeback threads are woken to
1880 		/* Start writeback even when in laptop mode */  in balance_dirty_pages()
2037  * dirty state and will initiate writeback if needed.
2111  * dirty state and will initiate writeback if needed.
2125  * and thresh, but it's for background writeback.
2156  * Determines whether background writeback should keep writing @wb or it's
2159  * Return: %true if writeback should continue.
2188 	 * Writing 0 to dirty_writeback_interval will disable periodic writeback  in dirty_writeback_centisecs_handler()
2189 	 * and a different non-zero value will wakeup the writeback threads.  in dirty_writeback_centisecs_handler()
2211  * We've spun up the disk and we're in laptop mode: schedule writeback
2222  * caused another writeback to be scheduled by laptop_io_completion.
2223  * Nothing needs to be written back anymore, so we unschedule the writeback.
2342  * Called early on to tune the page writeback dirty limits.
2361 	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/writeback:online",  in page_writeback_init()
2363 	cpuhp_setup_state(CPUHP_MM_WRITEBACK_DEAD, "mm/writeback:dead", NULL,  in page_writeback_init()
2371  * tag_pages_for_writeback - tag pages to be written by writeback
2378  * can then use the TOWRITE tag to identify pages eligible for writeback.
2379  * This mechanism is used to avoid livelocking of writeback by a process
2480  * writeback_iter - iterate folio of a mapping for writeback
2482  * @wbc: writeback context
2484  * @error: in-out pointer for writeback errors (see below)
2486  * This function returns the next folio for the writeback operation described by
2490  * To start the writeback operation, %NULL is passed in the @folio argument, and
2494  * If there was an error in the per-folio writeback inside the writeback_iter()
2497  * Once the writeback described in @wbc has finished, this function will return
2513 		 * For range cyclic writeback we remember where we stopped so  in writeback_iter()
2516 		 * For non-cyclic writeback we always start at the beginning of  in writeback_iter()
2529 		 * For data-integrity writeback we have to be careful so that we  in writeback_iter()
2544 		 * For integrity writeback we have to keep going until we have  in writeback_iter()
2545 		 * written all the folios we tagged for writeback above, even if  in writeback_iter()
2551 		 * For background writeback we exit as soon as we run past  in writeback_iter()
2566 		 * To avoid deadlocks between range_cyclic writeback and callers  in writeback_iter()
2568 		 * the writeback iteration finishes, we do not loop back to the  in writeback_iter()
2570 		 * writeback access order inversion - we should only ever lock  in writeback_iter()
2667 		 * Lacking an allocation context or the locality or writeback  in do_writepages()
2669 		 * writeback activity on the local node. It's as good a  in do_writepages()
2677 	 * but if there's constant writeback being submitted, this makes sure  in do_writepages()
2678 	 * writeback bandwidth is updated once in a while.  in do_writepages()
2730  * Helper function for deaccounting dirty page without writeback.
2809  * @wbc: The writeback control.
2971 		 *      cause the writeback.  in folio_clear_dirty_for_io()
3022 	 * Make sure estimate of writeback throughput gets updated after  in wb_inode_writeback_end()
3023 	 * writeback completed. We delay the update by BANDWIDTH_INTERVAL  in wb_inode_writeback_end()
3025 	 * that if multiple inodes end writeback at a similar time, they get  in wb_inode_writeback_end()
3125 	 * If writeback has been triggered on a page that cannot be made  in __folio_start_writeback()
3133  * folio_wait_writeback - Wait for a folio to finish writeback.
3141  * If the folio is not locked, writeback may start again after writeback
3154  * folio_wait_writeback_killable - Wait for a folio to finish writeback.
3162  * If the folio is not locked, writeback may start again after writeback
3179  * folio_wait_stable() - wait for writeback to finish, if necessary.
3183  * device that requires folio contents to be held stable during writeback.
3184  * If so, then it will wait for any pending writeback to complete.
3188  * If the folio is not locked, writeback may start again after writeback