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From: Greg KH on 10 May 2010 19:20
2.6.32-stable review patch. If anyone has any objections, please let us know.

------------------

From: Dan Williams <dan.j.williams(a)intel.com>

commit 5157b4aa5b7de8787b6318e61bcc285031bb9088 upstream.

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.

Acked-by: NeilBrown <neilb(a)suse.de>
Reported-by: H. Peter Anvin <hpa(a)zytor.com>
Signed-off-by: Dan Williams <dan.j.williams(a)intel.com>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

---
crypto/async_tx/async_raid6_recov.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)

--- a/crypto/async_tx/async_raid6_recov.c
+++ b/crypto/async_tx/async_raid6_recov.c
@@ -324,6 +324,7 @@ struct dma_async_tx_descriptor *
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 @@ async_raid6_2data_recov(int disks, size_

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 @@ async_raid6_datap_recov(int disks, size_

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++)


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Prev: [92/98] SCSI: fix locking around blk_abort_request()
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