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Commit e185dda8 authored by Wu Fengguang's avatar Wu Fengguang
Browse files

writeback: avoid extra sync work at enqueue time 



This removes writeback_control.wb_start and does more straightforward
sync livelock prevention by setting .older_than_this to prevent extra
inodes from being enqueued in the first place.

Acked-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
parent e8dfc305

fs/fs-writeback.c

+3 −13
Original line number Original line Diff line number Diff line
@@ -544,15 +544,6 @@ static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb, 
			continue;

			continue;

		}

		}





		/*

		 * Was this inode dirtied after sync_sb_inodes was called?

		 * This keeps sync from extra jobs and livelock.

		 */

		if (inode_dirtied_after(inode, wbc->wb_start)) {

			spin_unlock(&inode->i_lock);

			return 1;

		}



		__iget(inode);

		__iget(inode);





		pages_skipped = wbc->pages_skipped;

		pages_skipped = wbc->pages_skipped;
@@ -585,9 +576,6 @@ static void __writeback_inodes_wb(struct bdi_writeback *wb, 
{

{

	int ret = 0;

	int ret = 0;





	if (!wbc->wb_start)

		wbc->wb_start = jiffies; /* livelock avoidance */



	while (!list_empty(&wb->b_io)) {

	while (!list_empty(&wb->b_io)) {

		struct inode *inode = wb_inode(wb->b_io.prev);

		struct inode *inode = wb_inode(wb->b_io.prev);

		struct super_block *sb = inode->i_sb;

		struct super_block *sb = inode->i_sb;
@@ -686,7 +674,9 @@ static long wb_writeback(struct bdi_writeback *wb, 
	if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_writepages)

	if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_writepages)

		write_chunk = LONG_MAX;

		write_chunk = LONG_MAX;





	wbc.wb_start = jiffies; /* livelock avoidance */

	oldest_jif = jiffies;

	wbc.older_than_this = &oldest_jif;



	spin_lock(&wb->list_lock);

	spin_lock(&wb->list_lock);

	for (;;) {

	for (;;) {

		/*

		/*

include/linux/writeback.h

+0 −3
Original line number Original line Diff line number Diff line
@@ -26,9 +26,6 @@ struct writeback_control { 
	enum writeback_sync_modes sync_mode;

	enum writeback_sync_modes sync_mode;

	unsigned long *older_than_this;	/* If !NULL, only write back inodes

	unsigned long *older_than_this;	/* If !NULL, only write back inodes

					   older than this */

					   older than this */

	unsigned long wb_start;         /* Time writeback_inodes_wb was

					   called. This is needed to avoid

					   extra jobs and livelock */

	long nr_to_write;		/* Write this many pages, and decrement

	long nr_to_write;		/* Write this many pages, and decrement

					   this for each page written */

					   this for each page written */

	long pages_skipped;		/* Pages which were not written */

	long pages_skipped;		/* Pages which were not written */