raid6: fix recovery performance regression
The raid6 recovery code should immediately drop back to the optimized
synchronous path when a p+q dma resource is not available. Otherwise we
run the non-optimized/multi-pass async code in sync mode.
Verified with raid6test (NDISKS=255)
Applies to kernels >= 2.6.32.
Cc: <stable@kernel.org>
Acked-by: NeilBrown <neilb@suse.de>
Reported-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/crypto/async_tx/async_raid6_recov.c b/crypto/async_tx/async_raid6_recov.c
index 943f2ab..ce038d8 100644
--- a/crypto/async_tx/async_raid6_recov.c
+++ b/crypto/async_tx/async_raid6_recov.c
@@ -324,6 +324,7 @@
async_raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
struct page **blocks, struct async_submit_ctl *submit)
{
+ void *scribble = submit->scribble;
int non_zero_srcs, i;
BUG_ON(faila == failb);
@@ -332,11 +333,13 @@
pr_debug("%s: disks: %d len: %zu\n", __func__, disks, bytes);
- /* we need to preserve the contents of 'blocks' for the async
- * case, so punt to synchronous if a scribble buffer is not available
+ /* if a dma resource is not available or a scribble buffer is not
+ * available punt to the synchronous path. In the 'dma not
+ * available' case be sure to use the scribble buffer to
+ * preserve the content of 'blocks' as the caller intended.
*/
- if (!submit->scribble) {
- void **ptrs = (void **) blocks;
+ if (!async_dma_find_channel(DMA_PQ) || !scribble) {
+ void **ptrs = scribble ? scribble : (void **) blocks;
async_tx_quiesce(&submit->depend_tx);
for (i = 0; i < disks; i++)
@@ -406,11 +409,13 @@
pr_debug("%s: disks: %d len: %zu\n", __func__, disks, bytes);
- /* we need to preserve the contents of 'blocks' for the async
- * case, so punt to synchronous if a scribble buffer is not available
+ /* if a dma resource is not available or a scribble buffer is not
+ * available punt to the synchronous path. In the 'dma not
+ * available' case be sure to use the scribble buffer to
+ * preserve the content of 'blocks' as the caller intended.
*/
- if (!scribble) {
- void **ptrs = (void **) blocks;
+ if (!async_dma_find_channel(DMA_PQ) || !scribble) {
+ void **ptrs = scribble ? scribble : (void **) blocks;
async_tx_quiesce(&submit->depend_tx);
for (i = 0; i < disks; i++)