From 016eb4a0ed06a3677d67a584da901f0e9a63c666 Mon Sep 17 00:00:00 2001
From: Andrew Morton <akpm@osdl.org>
Date: Fri, 8 Sep 2006 09:48:38 -0700
Subject: [PATCH] [PATCH] invalidate_complete_page() race fix

If a CPU faults this page into pagetables after invalidate_mapping_pages()
checked page_mapped(), invalidate_complete_page() will still proceed to remove
the page from pagecache.  This leaves the page-faulting process with a
detached page.  If it was MAP_SHARED then file data loss will ensue.

Fix that up by checking the page's refcount after taking tree_lock.

Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
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