async_tx: fix kmap_atomic usage in async_memcpy

Andrew Morton:
	[async_memcpy] is very wrong if both ASYNC_TX_KMAP_DST and
	ASYNC_TX_KMAP_SRC can ever be set.  We'll end up using the same kmap
	slot for both src add dest and we get either corrupted data or a BUG.

Evgeniy Polyakov:
	Btw, shouldn't it always be kmap_atomic() even if flag is not set.
	That pages are usual one returned by alloc_page().

So fix the usage of kmap_atomic and kill the ASYNC_TX_KMAP_DST and
ASYNC_TX_KMAP_SRC flags.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index c8dfdb302916..d90ee145effe 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -493,12 +493,12 @@ async_copy_data(int frombio, struct bio *bio, struct page *page,
                         if (frombio)
                                 tx = async_memcpy(page, bio_page, page_offset,
                                         b_offset, clen,
-                                        ASYNC_TX_DEP_ACK | ASYNC_TX_KMAP_SRC,
+                                        ASYNC_TX_DEP_ACK,
                                         tx, NULL, NULL);
                         else
                                 tx = async_memcpy(bio_page, page, b_offset,
                                         page_offset, clen,
-                                        ASYNC_TX_DEP_ACK | ASYNC_TX_KMAP_DST,
+                                        ASYNC_TX_DEP_ACK,
                                         tx, NULL, NULL);
                 }
                 if (clen < len) /* hit end of page */