4.1-stable review patch.  If anyone has any objections, please let me know.

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

From: "Martin K. Petersen" <martin.petersen@oracle.com>

commit eab6ee1ce3c4678224d70338134f7a02005768cb upstream.

Commit 5d3abf8ff67f ("libata: Fall back to unqueued READ LOG EXT if
the DMA variant fails") allowed us to fall back to the unqueued READ
LOG variant if the queued version failed. However, if the device did
not support the page at all we would end up looping due to a merge
snafu.

Ensure we only take the fallback path once.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Reported-by: Sergey Senozhatsky <redacted>
Tested-by: Sergey Senozhatsky <redacted>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/ata/libata-eh.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c

@@ -1521,6 +1521,7 @@ retry:
 	} else {
 		tf.command = ATA_CMD_READ_LOG_EXT;
 		tf.protocol = ATA_PROT_PIO;
+		dma = false;
 	}
 	tf.lbal = log;
 	tf.lbam = page;