bounce: call flush_dcache_page() after bounce_copy_vec()

commit ac8456d6f9a3011c824176bd6084d39e5f70a382 upstream.

I have been seeing problems on Tegra 2 (ARMv7 SMP) systems with HIGHMEM
enabled on 2.6.35 (plus some patches targetted at 2.6.36 to perform cache
maintenance lazily), and the root cause appears to be that the mm bouncing
code is calling flush_dcache_page before it copies the bounce buffer into
the bio.

The bounced page needs to be flushed after data is copied into it, to
ensure that architecture implementations can synchronize instruction and
data caches if necessary.

Signed-off-by: Gary King <gking@nvidia.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Acked-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/mm/bounce.c b/mm/bounce.c
index b6d2d0f1019b3975640a5b0388825b44112be7de..e83e280357468ed850804aa89aac1b31ef54cedd 100644 (file)
--- a/mm/bounce.c
+++ b/mm/bounce.c
@@ -114,8 +114,8 @@ static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
                 */
                vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;
 
-               flush_dcache_page(tovec->bv_page);
                bounce_copy_vec(tovec, vfrom);
+               flush_dcache_page(tovec->bv_page);
        }
 }