linux-kernel - [PATCH 10/23] thp, mm: warn if we try to use replace_page_cache

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Date:	Sun,  4 Aug 2013 05:17:12 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Al Viro <viro@...iv.linux.org.uk>, Hugh Dickins <hughd@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Hillf Danton <dhillf@...il.com>, Dave Hansen <dave@...1.net>,
	Ning Qu <quning@...gle.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 10/23] thp, mm: warn if we try to use replace_page_cache_page() with THP

From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>

replace_page_cache_page() is only used by FUSE. It's unlikely that we
will support THP in FUSE page cache any soon.

Let's pospone implemetation of THP handling in replace_page_cache_page()
until any will use it. -EINVAL and WARN_ONCE() for now.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 mm/filemap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index b75bdf5..28f4927 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -418,6 +418,10 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 {
 	int error;
 
+	if (WARN_ONCE(PageTransHuge(old) || PageTransHuge(new),
+		     "unexpected transhuge page\n"))
+		return -EINVAL;
+
 	VM_BUG_ON(!PageLocked(old));
 	VM_BUG_ON(!PageLocked(new));
 	VM_BUG_ON(new->mapping);
-- 
1.8.3.2

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