Convert wbc.range_cyclic to new behavior: when past EOF, abort writeback
of the inode, which instructs writeback_single_inode() to delay it for
a while if necessary.
It removes one inefficient .range_cyclic IO pattern when writeback_index
wraps:
submit [10000-10100], (wrap), submit [0-100]
In which the submitted pages may be consisted of two distant ranges.
It also prevents submitting pointless IO for busy overwriters.
CC: Evgeniy Polyakov <zbr@xxxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
drivers/staging/pohmelfs/inode.c | 25 ++++++++-----------------
1 file changed, 8 insertions(+), 17 deletions(-)
--- linux.orig/drivers/staging/pohmelfs/inode.c 2009-10-06 23:37:49.000000000 +0800
+++ linux/drivers/staging/pohmelfs/inode.c 2009-10-06 23:38:31.000000000 +0800
@@ -149,7 +149,6 @@ static int pohmelfs_writepages(struct ad
int nr_pages;
pgoff_t index;
pgoff_t end; /* Inclusive */
- int scanned = 0;
int range_whole = 0;
if (wbc->range_cyclic) {
@@ -160,17 +159,18 @@ static int pohmelfs_writepages(struct ad
end = wbc->range_end >> PAGE_CACHE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
range_whole = 1;
- scanned = 1;
}
-retry:
+
while (!done && (index <= end)) {
unsigned int i = min(end - index, (pgoff_t)psb->trans_max_pages);
int path_len;
struct netfs_trans *trans;
err = pohmelfs_inode_has_dirty_pages(mapping, index);
- if (!err)
+ if (!err) {
+ index = 0;
break;
+ }
err = pohmelfs_path_length(pi);
if (err < 0)
@@ -197,15 +197,16 @@ retry:
dprintk("%s: t: %p, nr_pages: %u, end: %lu, index: %lu, max: %u.\n",
__func__, trans, nr_pages, end, index, trans->page_num);
- if (!nr_pages)
+ if (!nr_pages) {
+ index = 0;
goto err_out_reset;
+ }
err = pohmelfs_write_inode_create(inode, trans);
if (err)
goto err_out_reset;
err = 0;
- scanned = 1;
for (i = 0; i < trans->page_num; i++) {
struct page *page = trans->pages[i];
@@ -215,7 +216,7 @@ retry:
if (unlikely(page->mapping != mapping))
goto out_continue;
- if (!wbc->range_cyclic && page->index > end) {
+ if (page->index > end) {
done = 1;
goto out_continue;
}
@@ -263,16 +264,6 @@ err_out_reset:
break;
}
- if (!scanned && !done) {
- /*
- * We hit the last page and there is more work to be done: wrap
- * back to the start of the file
- */
- scanned = 1;
- index = 0;
- goto retry;
- }
-
if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
mapping->writeback_index = index;
--
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