[PATCH] AOP_TRUNCATED_PAGE victims in read_pages() belong in the LRU
AOP_TRUNCATED_PAGE victims in read_pages() belong in the LRU
Nick Piggin rightly pointed out that the introduction of AOP_TRUNCATED_PAGE
to read_pages() was wrong to leave A_T_P victim pages in the page cache but
not put them in the LRU. Failing to do so hid them from the VM.
A_T_P just means that the aop method unlocked the page rather than
performing IO. It would be very rare that the page was truncated between
the unlock and testing A_T_P. So we leave the pages in the LRU for likely
reuse soon rather than backing them back out of the page cache. We do this
by matching the behaviour before the A_T_P introduction which added pages
to the LRU regardless of what ->readpage() did.
This doesn't include the unrelated cleanup in Nick's initial fix which
changed read_pages() to return void to match its only caller's behaviour of
ignoring errors.
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Zach Brown <zach.brown@oracle.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/readahead.c b/mm/readahead.c
index 0f142a4..4ee52ca 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -182,14 +182,11 @@
list_del(&page->lru);
if (!add_to_page_cache(page, mapping,
page->index, GFP_KERNEL)) {
- ret = mapping->a_ops->readpage(filp, page);
- if (ret != AOP_TRUNCATED_PAGE) {
- if (!pagevec_add(&lru_pvec, page))
- __pagevec_lru_add(&lru_pvec);
- continue;
- } /* else fall through to release */
- }
- page_cache_release(page);
+ mapping->a_ops->readpage(filp, page);
+ if (!pagevec_add(&lru_pvec, page))
+ __pagevec_lru_add(&lru_pvec);
+ } else
+ page_cache_release(page);
}
pagevec_lru_add(&lru_pvec);
ret = 0;