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ext4: update writeback_index based on last page scanned

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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: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Eric Sandeen 2010-10-27 21:30:13 -04:00 committed by Theodore Ts'o
parent 5b41d92437
commit 72f84e6560
1 changed files with 9 additions and 5 deletions
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14
fs/ext4/inode.c
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@ -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 @@ retry:
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 @@ retry:
__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;