[PATCHv3 13/41] truncate: make sure invalidate_mapping_pages() can discard huge pages

Kirill A. Shutemov
2016-09-15T11:54:55Z

invalidate_inode_page() has expectation about page_count() of the page
-- if it's not 2 (one to caller, one to radix-tree), it will not be
dropped. That condition almost never met for THPs -- tail pages are
pinned to the pagevec.

Let's drop them, before calling invalidate_inode_page().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
mm/truncate.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/mm/truncate.c b/mm/truncate.c
index a01cce450a26..ce904e4b1708 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -504,10 +504,21 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
/* 'end' is in the middle of THP */
if (index == round_down(end, HPAGE_PMD_NR))
continue;
+ /*
+ * invalidate_inode_page() expects
+ * page_count(page) == 2 to drop page from page
+ * cache -- drop tail pages references.
+ */
+ get_page(page);
+ pagevec_release(&pvec);
}

ret = invalidate_inode_page(page);
unlock_page(page);
+
+ if (PageTransHuge(page))
+ put_page(page);
+
/*
* Invalidation is a hint that the page is no longer
* of interest and try to speed up its reclaim.