[PATCH 3.13.y-ckt 023/122] SCSI: add 1024 max sectors black list flag

From: Kamal Mostafa
Date: Wed Jun 17 2015 - 18:57:00 EST

3.13.11-ckt22 -stable review patch. If anyone has any objections, please let me know.


From: Mike Christie <michaelc@xxxxxxxxxxx>

commit 35e9a9f93994d7f7d12afa41169c7ba05513721b upstream.

This works around a issue with qnap iscsi targets not handling large IOs
very well.

The target returns:

VPD INQUIRY: Block limits page (SBC)
Maximum compare and write length: 1 blocks
Optimal transfer length granularity: 1 blocks
Maximum transfer length: 4294967295 blocks
Optimal transfer length: 4294967295 blocks
Maximum prefetch, xdread, xdwrite transfer length: 0 blocks
Maximum unmap LBA count: 8388607
Maximum unmap block descriptor count: 1
Optimal unmap granularity: 16383
Unmap granularity alignment valid: 0
Unmap granularity alignment: 0
Maximum write same length: 0xffffffff blocks
Maximum atomic transfer length: 0
Atomic alignment: 0
Atomic transfer length granularity: 0

and it is *sometimes* able to handle at least one IO of size up to 8 MB. We
have seen in traces where it will sometimes work, but other times it
looks like it fails and it looks like it returns failures if we send
multiple large IOs sometimes. Also it looks like it can return 2 different
errors. It will sometimes send iscsi reject errors indicating out of
resources or it will send invalid cdb illegal requests check conditions.
And then when it sends iscsi rejects it does not seem to handle retries
when there are command sequence holes, so I could not just add code to
try and gracefully handle that error code.

The problem is that we do not have a good contact for the company,
so we are not able to determine under what conditions it returns
which error and why it sometimes works.

So, this patch just adds a new black list flag to set targets like this to
the old max safe sectors of 1024. The max_hw_sectors changes added in 3.19
caused this regression, so I also ccing stable.

Reported-by: Christian Hesse <list@xxxxxxxx>
Signed-off-by: Mike Christie <michaelc@xxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: James Bottomley <JBottomley@xxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
drivers/scsi/scsi_devinfo.c | 1 +
drivers/scsi/scsi_scan.c | 6 ++++++
include/scsi/scsi_devinfo.h | 1 +
3 files changed, 8 insertions(+)

diff --git a/drivers/scsi/scsi_devinfo.c b/drivers/scsi/scsi_devinfo.c
index 262ab83..9f77d23 100644
--- a/drivers/scsi/scsi_devinfo.c
+++ b/drivers/scsi/scsi_devinfo.c
@@ -226,6 +226,7 @@ static struct {
{"Promise", "VTrak E610f", NULL, BLIST_SPARSELUN | BLIST_NO_RSOC},
{"Promise", "", NULL, BLIST_SPARSELUN},
+ {"QNAP", "iSCSI Storage", NULL, BLIST_MAX_1024},
{"QUANTUM", "XP34301", "1071", BLIST_NOTQ},
{"SanDisk", "ImageMate CF-SD1", NULL, BLIST_FORCELUN},
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index f194e43..1d311d8 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -876,6 +876,12 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
if (*bflags & BLIST_MAX_512)
blk_queue_max_hw_sectors(sdev->request_queue, 512);
+ /*
+ * Max 1024 sector transfer length for targets that report incorrect
+ * max/optimal lengths and relied on the old block layer safe default
+ */
+ else if (*bflags & BLIST_MAX_1024)
+ blk_queue_max_hw_sectors(sdev->request_queue, 1024);

* Some devices may not want to have a start command automatically
diff --git a/include/scsi/scsi_devinfo.h b/include/scsi/scsi_devinfo.h
index 428b023..c67cd3e 100644
--- a/include/scsi/scsi_devinfo.h
+++ b/include/scsi/scsi_devinfo.h
@@ -34,5 +34,6 @@
#define BLIST_SKIP_VPD_PAGES 0x4000000 /* Ignore SBC-3 VPD pages */
#define BLIST_TRY_VPD_PAGES 0x10000000 /* Attempt to read VPD pages */
#define BLIST_NO_RSOC 0x20000000 /* don't try to issue RSOC */
+#define BLIST_MAX_1024 0x40000000 /* maximum 1024 sector cdb length */


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