Commit 9f1a3cfc authored Jun 25, 2006 by Zach Brown Committed by Linus Torvalds Jun 25, 2006

[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>

parent 09a9a45d

mm/readahead.c

+5 −8

Original line number	Diff line number	Diff line
		@@ -182,13 +182,10 @@ static int read_pages(struct address_space mapping, struct file filp,
		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) {
		mapping->a_ops->readpage(filp, page);
		if (!pagevec_add(&lru_pvec, page))
		__pagevec_lru_add(&lru_pvec);
		continue;
		} /* else fall through to release */
		}
		} else
		page_cache_release(page);
		}
		pagevec_lru_add(&lru_pvec);