Get rid of some complex expressions from flow control statements, add a
comment, remove some duplicate code.
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
---
Index: linux-2.6/mm/page-writeback.c
===================================================================
--- linux-2.6.orig/mm/page-writeback.c
+++ linux-2.6/mm/page-writeback.c
@@ -900,11 +900,14 @@ int write_cache_pages(struct address_spa
cycled = 1; /* ignore range_cyclic tests */
}
retry:
- while (!done && (index <= end) &&
- (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
- PAGECACHE_TAG_DIRTY,
- min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
- unsigned i;
+ while (!done && (index <= end)) {
+ int i;
+
+ nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
+ PAGECACHE_TAG_DIRTY,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1);
+ if (nr_pages == 0)
+ break;
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
@@ -919,7 +922,16 @@ retry:
again:
lock_page(page);
+ /*
+ * Page truncated or invalidated. We can freely skip it
+ * then, even for data integrity operations: the page
+ * has disappeared concurrently, so there could be no
+ * real expectation of this data interity operation
+ * even if there is now a new, dirty page at the same
+ * pagecache address.
+ */
if (unlikely(page->mapping != mapping)) {
+continue_unlock:
unlock_page(page);
continue;
}
@@ -927,18 +939,15 @@ again:
if (page->index > end) {
/* Can't be range_cyclic: end == -1 there */
done = 1;
- unlock_page(page);
- continue;
+ goto continue_unlock;
}
if (wbc->sync_mode != WB_SYNC_NONE)
wait_on_page_writeback(page);
if (PageWriteback(page) ||
- !clear_page_dirty_for_io(page)) {
- unlock_page(page);
- continue;
- }
+ !clear_page_dirty_for_io(page))
+ goto continue_unlock;
ret = (*writepage)(page, wbc, data);
if (unlikely(ret)) {
@@ -952,7 +961,8 @@ again:
break;
}
if (wbc->sync_mode == WB_SYNC_NONE) {
- if (--(wbc->nr_to_write) <= 0)
+ wbc->nr_to_write--;
+ if (wbc->nr_to_write <= 0)
done = 1;
}
if (wbc->nonblocking && bdi_write_congested(bdi)) {
--
--
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