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 a2b76a588e348e0d46f2bfed4131af6ac3eea86b..1d5fa0870ca91d2692894506549e0dec22275f7a 100644 (file)
--- a/mm/bounce.c
+++ b/mm/bounce.c
@@ -115,8 +115,8 @@ 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);
        }
 }