Patch "scsi: mpt3sas: Force request partial completion alignment" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

scsi: mpt3sas: Force request partial completion alignment

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
scsi-mpt3sas-force-request-partial-completion-alignment.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Ram Pai <[email protected]>
Date: Thu, 26 Jan 2017 16:37:01 -0200
Subject: scsi: mpt3sas: Force request partial completion alignment

From: Ram Pai <[email protected]>

commit f2e767bb5d6ee0d988cb7d4e54b0b21175802b6b upstream.

The firmware or device, possibly under a heavy I/O load, can return on a partial unaligned boundary. Scsi-ml expects these requests to be completed on an alignment boundary. Scsi-ml blindly requeues the I/O without checking the alignment boundary of the I/O request for the remaining bytes. This leads to errors, since devices cannot perform non-aligned read/write operations.

This patch fixes the issue in the driver. It aligns unaligned completions of FS requests, by truncating them to the nearest alignment boundary.

[mkp: simplified if statement]

---
 drivers/scsi/mpt3sas/mpt3sas_scsih.c |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

@@ -4634,6 +4634,7 @@ _scsih_io_done(struct MPT3SAS_ADAPTER *i
 	struct MPT3SAS_DEVICE *sas_device_priv_data;
 	u32 response_code = 0;
 	unsigned long flags;
+	unsigned int sector_sz;
 
 	mpi_reply = mpt3sas_base_get_reply_virt_addr(ioc, reply);
 	scmd = _scsih_scsi_lookup_get_clear(ioc, smid);

@@ -4692,6 +4693,20 @@ _scsih_io_done(struct MPT3SAS_ADAPTER *i
 	}
 
 	xfer_cnt = le32_to_cpu(mpi_reply->TransferCount);
+
+	/* In case of bogus fw or device, we could end up having
+	 * unaligned partial completion. We can force alignment here,
+	 * then scsi-ml does not need to handle this misbehavior.
+	 */
+	sector_sz = scmd->device->sector_size;
+	if (unlikely(scmd->request->cmd_type == REQ_TYPE_FS && sector_sz &&
+		     xfer_cnt % sector_sz)) {
+		sdev_printk(KERN_INFO, scmd->device,
+		    "unaligned partial completion avoided (xfer_cnt=%u, sector_sz=%u)\n",
+			    xfer_cnt, sector_sz);
+		xfer_cnt = round_down(xfer_cnt, sector_sz);
+	}
+
 	scsi_set_resid(scmd, scsi_bufflen(scmd) - xfer_cnt);
 	if (ioc_status & MPI2_IOCSTATUS_FLAG_LOG_INFO_AVAILABLE)
 		log_info =  le32_to_cpu(mpi_reply->IOCLogInfo);

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/scsi-mpt3sas-force-request-partial-completion-alignment.patch