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Commit 72f84e65 authored by Eric Sandeen's avatar Eric Sandeen Committed by Theodore Ts'o
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ext4: update writeback_index based on last page scanned 



As pointed out in a prior patch, updating the mapping's
writeback_index based on pages written isn't quite right;
what the writeback index is really supposed to reflect is
the next page which should be scanned for writeback during
periodic flush.

As in write_cache_pages(), write_cache_pages_da() does
this scanning for us as we assemble the mpd for later
writeout.  If we keep track of the next page after the
current scan, we can easily update writeback_index without
worrying about pages written vs. pages skipped, etc.

Without this, an fsync will reset writeback_index to
0 (its starting index) + however many pages it wrote, which
can mess up the progress of periodic flush.

Signed-off-by: default avatarEric Sandeen <sandeen@redhat.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 5b41d924

fs/ext4/inode.c

+9 −5
Original line number Diff line number Diff line
@@ -2800,12 +2800,13 @@ static int ext4_da_writepages_trans_blocks(struct inode *inode) 
 */

static int write_cache_pages_da(struct address_space *mapping,

				struct writeback_control *wbc,

				struct mpage_da_data *mpd)

				struct mpage_da_data *mpd,

				pgoff_t *done_index)

{

	int ret = 0;

	int done = 0;

	struct pagevec pvec;

	int nr_pages;

	unsigned nr_pages;

	pgoff_t index;

	pgoff_t end;		/* Inclusive */

	long nr_to_write = wbc->nr_to_write;
@@ -2820,6 +2821,7 @@ static int write_cache_pages_da(struct address_space *mapping, 
	else

		tag = PAGECACHE_TAG_DIRTY;



	*done_index = index;

	while (!done && (index <= end)) {

		int i;
@@ -2843,6 +2845,8 @@ static int write_cache_pages_da(struct address_space *mapping, 
				break;

			}



			*done_index = page->index + 1;



			lock_page(page);



			/*
@@ -2928,6 +2932,7 @@ static int ext4_da_writepages(struct address_space *mapping, 
	long desired_nr_to_write, nr_to_writebump = 0;

	loff_t range_start = wbc->range_start;

	struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);

	pgoff_t done_index = 0;

	pgoff_t end;



	trace_ext4_da_writepages(inode, wbc);
@@ -3050,7 +3055,7 @@ static int ext4_da_writepages(struct address_space *mapping, 
		mpd.io_done = 0;

		mpd.pages_written = 0;

		mpd.retval = 0;

		ret = write_cache_pages_da(mapping, wbc, &mpd);

		ret = write_cache_pages_da(mapping, wbc, &mpd, &done_index);

		/*

		 * If we have a contiguous extent of pages and we

		 * haven't done the I/O yet, map the blocks and submit
@@ -3104,14 +3109,13 @@ static int ext4_da_writepages(struct address_space *mapping, 
			 __func__, wbc->nr_to_write, ret);



	/* Update index */

	index += pages_written;

	wbc->range_cyclic = range_cyclic;

	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))

		/*

		 * set the writeback_index so that range_cyclic

		 * mode will write it back later

		 */

		mapping->writeback_index = index;

		mapping->writeback_index = done_index;



out_writepages:

	wbc->nr_to_write -= nr_to_writebump;