linux-kernel - [001/165] tmpfs: fix highmem swapoff crash regression

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Message-Id: <20110601081047.776958419@blue.kroah.org>
Date:	Wed, 01 Jun 2011 17:09:31 +0900
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Hugh Dickins <hughd@...gle.com>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [001/165] tmpfs: fix highmem swapoff crash regression

2.6.39-stable review patch.  If anyone has any objections, please let us know.

------------------
Content-Length: 1204
Lines: 45

From: Hugh Dickins <hughd@...gle.com>

commit e6c9366b2adb52cba64b359b3050200743c7568c upstream.

Commit 778dd893ae78 ("tmpfs: fix race between umount and swapoff")
forgot the new rules for strict atomic kmap nesting, causing

  WARNING: at arch/x86/mm/highmem_32.c:81

from __kunmap_atomic(), then

  BUG: unable to handle kernel paging request at fffb9000

from shmem_swp_set() when shmem_unuse_inode() is handling swapoff with
highmem in use.  My disgrace again.

See
  https://bugzilla.kernel.org/show_bug.cgi?id=35352

Reported-by: Witold Baryluk <baryluk@....if.uj.edu.pl>
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 mm/shmem.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -916,11 +916,12 @@ static int shmem_unuse_inode(struct shme
 			if (size > ENTRIES_PER_PAGE)
 				size = ENTRIES_PER_PAGE;
 			offset = shmem_find_swp(entry, ptr, ptr+size);
+			shmem_swp_unmap(ptr);
 			if (offset >= 0) {
 				shmem_dir_unmap(dir);
+				ptr = shmem_swp_map(subdir);
 				goto found;
 			}
-			shmem_swp_unmap(ptr);
 		}
 	}
 lost1:


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