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>

3 files changed, 6 insertions, 23 deletions

diff --git a/crypto/async_tx/async_memcpy.c b/crypto/async_tx/async_memcpy.c
index a973f4ef897d..047e533fcc5b 100644
--- a/crypto/async_tx/async_memcpy.c
+++ b/crypto/async_tx/async_memcpy.c
@@ -36,7 +36,6 @@
  * @offset: offset in pages to start transaction
  * @len: length in bytes
  * @flags: ASYNC_TX_ASSUME_COHERENT, ASYNC_TX_ACK, ASYNC_TX_DEP_ACK,
- *      ASYNC_TX_KMAP_SRC, ASYNC_TX_KMAP_DST
  * @depend_tx: memcpy depends on the result of this transaction
  * @cb_fn: function to call when the memcpy completes
  * @cb_param: parameter to pass to the callback routine
@@ -88,23 +87,13 @@ async_memcpy(struct page *dest, struct page *src, unsigned int dest_offset,
                                         __FUNCTION__);
                 }
 
-                if (flags & ASYNC_TX_KMAP_DST)
-                        dest_buf = kmap_atomic(dest, KM_USER0) + dest_offset;
-                else
-                        dest_buf = page_address(dest) + dest_offset;
-
-                if (flags & ASYNC_TX_KMAP_SRC)
-                        src_buf = kmap_atomic(src, KM_USER0) + src_offset;
-                else
-                        src_buf = page_address(src) + src_offset;
+                dest_buf = kmap_atomic(dest, KM_USER0) + dest_offset;
+                src_buf = kmap_atomic(src, KM_USER1) + src_offset;
 
                 memcpy(dest_buf, src_buf, len);
 
-                if (flags & ASYNC_TX_KMAP_DST)
-                        kunmap_atomic(dest_buf, KM_USER0);
-
-                if (flags & ASYNC_TX_KMAP_SRC)
-                        kunmap_atomic(src_buf, KM_USER0);
+                kunmap_atomic(dest_buf, KM_USER0);
+                kunmap_atomic(src_buf, KM_USER1);
 
                 async_tx_sync_epilog(flags, depend_tx, cb_fn, cb_param);
         }
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 */
diff --git a/include/linux/async_tx.h b/include/linux/async_tx.h
index ff1255079fa1..bdca3f1b3213 100644
--- a/include/linux/async_tx.h
+++ b/include/linux/async_tx.h
@@ -51,10 +51,6 @@ struct dma_chan_ref {
  * @ASYNC_TX_ACK: immediately ack the descriptor, precludes setting up a
  * dependency chain
  * @ASYNC_TX_DEP_ACK: ack the dependency descriptor.  Useful for chaining.
- * @ASYNC_TX_KMAP_SRC: if the transaction is to be performed synchronously
- * take an atomic mapping (KM_USER0) on the source page(s)
- * @ASYNC_TX_KMAP_DST: if the transaction is to be performed synchronously
- * take an atomic mapping (KM_USER0) on the dest page(s)
  */
 enum async_tx_flags {
         ASYNC_TX_XOR_ZERO_DST    = (1 << 0),
@@ -62,8 +58,6 @@ enum async_tx_flags {
         ASYNC_TX_ASSUME_COHERENT = (1 << 2),
         ASYNC_TX_ACK             = (1 << 3),
         ASYNC_TX_DEP_ACK         = (1 << 4),
-        ASYNC_TX_KMAP_SRC        = (1 << 5),
-        ASYNC_TX_KMAP_DST        = (1 << 6),
 };
 
 #ifdef CONFIG_DMA_ENGINE