Convert wbc.range_cyclic to new behavior: when past EOF, abort the
writeback of the current inode, which instructs writeback_single_inode()
to delay it for a while if necessary.
This is the right behavior for
- sync writeback (is already so with range_whole)
we have scanned the inode address space, and don't care any more newly
dirtied pages. So shall update its i_dirtied_when and exclude it from
the todo list.
- periodic writeback
any more newly dirtied pages may be delayed for a while.
This also prevents pointless IO for busy overwriters.
- background writeback
irrelevant because it generally don't care the dirty timestamp.
That should get rid of one inefficient IO pattern of .range_cyclic when
writeback_index wraps, in which the submitted pages may be consisted of
two distant ranges: submit [10000-10100], (wrap), submit [0-100].
CC: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
CC: Jens Axboe <jens.axboe@xxxxxxxxxx>
CC: Nick Piggin <npiggin@xxxxxxx>
CC: Jan Kara <jack@xxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
mm/page-writeback.c | 27 +++++----------------------
1 file changed, 5 insertions(+), 22 deletions(-)
--- linux.orig/mm/page-writeback.c 2009-10-06 23:38:18.000000000 +0800
+++ linux/mm/page-writeback.c 2009-10-06 23:38:30.000000000 +0800
@@ -789,31 +789,23 @@ int write_cache_pages(struct address_spa
int done = 0;
struct pagevec pvec;
int nr_pages;
- pgoff_t uninitialized_var(writeback_index);
pgoff_t index;
pgoff_t end; /* Inclusive */
pgoff_t done_index;
- int cycled;
int range_whole = 0;
long nr_to_write = wbc->nr_to_write;
pagevec_init(&pvec, 0);
if (wbc->range_cyclic) {
- writeback_index = mapping->writeback_index; /* prev offset */
- index = writeback_index;
- if (index == 0)
- cycled = 1;
- else
- cycled = 0;
+ index = mapping->writeback_index; /* prev offset */
end = -1;
} else {
index = wbc->range_start >> PAGE_CACHE_SHIFT;
end = wbc->range_end >> PAGE_CACHE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
range_whole = 1;
- cycled = 1; /* ignore range_cyclic tests */
}
-retry:
+
done_index = index;
while (!done && (index <= end)) {
int i;
@@ -821,8 +813,10 @@ retry:
nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
PAGECACHE_TAG_DIRTY,
min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
- if (nr_pages == 0)
+ if (nr_pages == 0) {
+ done_index = 0;
break;
+ }
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
@@ -919,17 +913,6 @@ continue_unlock:
pagevec_release(&pvec);
cond_resched();
}
- if (!cycled && !done) {
- /*
- * range_cyclic:
- * We hit the last page and there is more work to be done: wrap
- * back to the start of the file
- */
- cycled = 1;
- index = 0;
- end = writeback_index - 1;
- goto retry;
- }
if (!wbc->no_nrwrite_index_update) {
if (wbc->range_cyclic || (range_whole && nr_to_write > 0))
mapping->writeback_index = done_index;
--
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