The range_cyclic writeback mode uses the address_space writeback_index
as the start index for writeback. With delayed allocation we were
updating writeback_index wrongly resulting in highly fragmented file.
Number of extents reduced from 4000 to 27 for a 3GB file with the below
patch.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
---
fs/ext4/inode.c | 83 +++++++++++++++++++++++++++++++++----------------------
1 files changed, 50 insertions(+), 33 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index cba7960..844c136 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1648,6 +1648,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
int ret = 0, err, nr_pages, i;
unsigned long index, end;
struct pagevec pvec;
+ long pages_skipped;
BUG_ON(mpd->next_page <= mpd->first_page);
pagevec_init(&pvec, 0);
@@ -1655,7 +1656,6 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
end = mpd->next_page - 1;
while (index <= end) {
- /* XXX: optimize tail */
/*
* We can use PAGECACHE_TAG_DIRTY lookup here because
* even though we have cleared the dirty flag on the page
@@ -1673,8 +1673,13 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
+ pages_skipped = mpd->wbc->pages_skipped;
err = mapping->a_ops->writepage(page, mpd->wbc);
- if (!err)
+ if (!err && (pages_skipped == mpd->wbc->pages_skipped))
+ /*
+ * have successfully written the page
+ * without skipping the same
+ */
mpd->pages_written++;
/*
* In error case, we have to continue because
@@ -2110,7 +2115,6 @@ static int mpage_da_writepages(struct address_space *mapping,
struct writeback_control *wbc,
struct mpage_da_data *mpd)
{
- long to_write;
int ret;
if (!mpd->get_block)
@@ -2125,10 +2129,7 @@ static int mpage_da_writepages(struct address_space *mapping,
mpd->pages_written = 0;
mpd->retval = 0;
- to_write = wbc->nr_to_write;
-
ret = write_cache_pages(mapping, wbc, __mpage_da_writepage, mpd);
-
/*
* Handle last extent of pages
*/
@@ -2137,7 +2138,7 @@ static int mpage_da_writepages(struct address_space *mapping,
mpage_da_submit_io(mpd);
}
- wbc->nr_to_write = to_write - mpd->pages_written;
+ wbc->nr_to_write -= mpd->pages_written;
return ret;
}
@@ -2366,11 +2367,14 @@ static int ext4_da_writepages_trans_blocks(struct inode *inode)
static int ext4_da_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
+ pgoff_t index;
+ int range_whole = 0;
handle_t *handle = NULL;
+ long pages_written = 0;
struct mpage_da_data mpd;
struct inode *inode = mapping->host;
+ int no_nrwrite_update, no_index_update;
int needed_blocks, ret = 0, nr_to_writebump = 0;
- long to_write, pages_skipped = 0;
struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
/*
@@ -2390,16 +2394,27 @@ static int ext4_da_writepages(struct address_space *mapping,
nr_to_writebump = sbi->s_mb_stream_request - wbc->nr_to_write;
wbc->nr_to_write = sbi->s_mb_stream_request;
}
+ if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
+ range_whole = 1;
-
- pages_skipped = wbc->pages_skipped;
+ if (wbc->range_cyclic)
+ index = mapping->writeback_index;
+ else
+ index = wbc->range_start >> PAGE_CACHE_SHIFT;
mpd.wbc = wbc;
mpd.inode = mapping->host;
-restart_loop:
- to_write = wbc->nr_to_write;
- while (!ret && to_write > 0) {
+ /*
+ * we don't want write_cache_pages to update
+ * nr_to_write and writeback_index
+ */
+ no_nrwrite_update = wbc->no_nrwrite_update;
+ wbc->no_nrwrite_update = 1;
+ no_index_update = wbc->no_index_update;
+ wbc->no_index_update = 1;
+
+ while (!ret && wbc->nr_to_write > 0) {
/*
* we insert one extent at a time. So we need
@@ -2420,46 +2435,48 @@ static int ext4_da_writepages(struct address_space *mapping,
dump_stack();
goto out_writepages;
}
- to_write -= wbc->nr_to_write;
-
mpd.get_block = ext4_da_get_block_write;
ret = mpage_da_writepages(mapping, wbc, &mpd);
ext4_journal_stop(handle);
- if (mpd.retval == -ENOSPC)
+ if (mpd.retval == -ENOSPC) {
+ /* commit the transaction which would
+ * free blocks released in the transaction
+ * and try again
+ */
jbd2_journal_force_commit_nested(sbi->s_journal);
-
- /* reset the retry count */
- if (ret == MPAGE_DA_EXTENT_TAIL) {
+ ret = 0;
+ } else if (ret == MPAGE_DA_EXTENT_TAIL) {
/*
* got one extent now try with
* rest of the pages
*/
- to_write += wbc->nr_to_write;
+ pages_written += mpd.pages_written;
ret = 0;
- } else if (wbc->nr_to_write) {
+ } else if (wbc->nr_to_write)
/*
* There is no more writeout needed
* or we requested for a noblocking writeout
* and we found the device congested
*/
- to_write += wbc->nr_to_write;
break;
- }
- wbc->nr_to_write = to_write;
- }
-
- if (!wbc->range_cyclic && (pages_skipped != wbc->pages_skipped)) {
- /* We skipped pages in this loop */
- wbc->nr_to_write = to_write +
- wbc->pages_skipped - pages_skipped;
- wbc->pages_skipped = pages_skipped;
- goto restart_loop;
}
+ /* Update index */
+ index += pages_written;
+ 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;
out_writepages:
- wbc->nr_to_write = to_write - nr_to_writebump;
+ if (!no_nrwrite_update)
+ wbc->no_nrwrite_update = 0;
+ if (!no_index_update)
+ wbc->no_index_update = 0;
+ wbc->nr_to_write -= nr_to_writebump;
return ret;
}
--
1.6.0.2.514.g23abd3
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