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ext4: Fix file fragmentation during large file write. 

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.
This patch reduces the number of extents reduced from 4000 to 27 for a
3GB file.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Aneesh Kumar K.V 2008-10-16 10:10:36 -04:00 committed by Theodore Ts'o
parent 17bc6c30cf
commit 22208dedbd
1 changed files with 56 additions and 33 deletions
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89
fs/ext4/inode.c
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@ -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)
@ -2125,19 +2129,18 @@ 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
*/
if (!mpd->io_done && mpd->next_page != mpd->first_page) {
if (mpage_da_map_blocks(mpd) == 0)
mpage_da_submit_io(mpd);
}
wbc->nr_to_write = to_write - mpd->pages_written;
mpd->io_done = 1;
ret = MPAGE_DA_EXTENT_TAIL;
}
wbc->nr_to_write -= mpd->pages_written;
return ret;
}
@ -2366,11 +2369,14 @@ 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;
struct mpage_da_data mpd;
struct inode *inode = mapping->host;
int no_nrwrite_index_update;
long pages_written = 0, pages_skipped;
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 +2396,26 @@ 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_index_update = wbc->no_nrwrite_index_update;
wbc->no_nrwrite_index_update = 1;
pages_skipped = wbc->pages_skipped;
while (!ret && wbc->nr_to_write > 0) {
/*
* we insert one extent at a time. So we need
@ -2420,46 +2436,53 @@ restart_loop:
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) {
wbc->pages_skipped = pages_skipped;
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;
wbc->pages_skipped = pages_skipped;
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 (pages_skipped != wbc->pages_skipped)
printk(KERN_EMERG "This should not happen leaving %s "
"with nr_to_write = %ld ret = %d\n",
__func__, wbc->nr_to_write, ret);
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_index_update)
wbc->no_nrwrite_index_update = 0;
wbc->nr_to_write -= nr_to_writebump;
return ret;
}