[PATCH] scsi disk: Reduce buffer size for vpd request

[Bernd Schubert <bernd.schubert@fastmail.fm>]

From: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>

Somehow older areca firmware versions have issues with 
scsi_get_vpd_page() and a large buffer, the firmware
seems to crash and the scsi error-handler will start endless 
recovery retries.
Limiting the buf-size to 64-bytes fixes this issue with older
firmware versions (<1.49 for my controller).

Fixes a regression with areca controllers and older firmware versions
introduced by commit: 66c28f97120e8a621afd5aa7a31c4b85c547d33d

Reported-by: Nix <nix@esperi.org.uk>
Tested-by: Nix <nix@esperi.org.uk>
Signed-off-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
CC: stable@vger.kernel.org
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>

---
 drivers/scsi/sd.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index b58e8f8..09a599f 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2644,13 +2644,16 @@ static void sd_read_write_same(struct scsi_disk *sdkp, unsigned char *buffer)
 	struct scsi_device *sdev = sdkp->device;
 
 	if (scsi_report_opcode(sdev, buffer, SD_BUF_SIZE, INQUIRY) < 0) {
+		/* too large values might cause issues with arcmsr */
+		int vpd_buf_len = 64;
+
 		sdev->no_report_opcodes = 1;
 
 		/* Disable WRITE SAME if REPORT SUPPORTED OPERATION
 		 * CODES is unsupported and the device has an ATA
 		 * Information VPD page (SAT).
 		 */
-		if (!scsi_get_vpd_page(sdev, 0x89, buffer, SD_BUF_SIZE))
+		if (!scsi_get_vpd_page(sdev, 0x89, buffer, vpd_buf_len))
 			sdev->no_write_same = 1;
 	}