[PATCH 08/14] scsi: sd: Optimal I/O size should be a multiple of reported granularity

Martin K. Petersen
2022-03-02T05:36:42Z

Commit a83da8a4509d ("scsi: sd: Optimal I/O size should be a multiple of
physical block size") validated the reported optimal I/O size against the
physical block size to overcome problems with devices reporting nonsensical
transfer sizes.

However, some devices claim conformity to older SCSI versions that predate
the physical block size being reported. Other devices do not report a
physical block size at all. We need to be able to validate the optimal I/O
size on those devices as well.

Many devices report an OPTIMAL TRANSFER LENGTH GRANULARITY in the same VPD
page as the OPTIMAL TRANSFER LENGTH. Use this value to validate the optimal
I/O size. Also check that the reported granularity is a multiple of the
physical block size, if supported.

Link: https://lore.kernel.org/r/33fb522e-4f61-1b76-914f-c9e6a3553c9b@gmail.com
Reported-by: Bernhard Sulzer <micraft.b@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
---
drivers/scsi/sd.c | 45 +++++++++++++++++++++++++++++++++++++++++----
drivers/scsi/sd.h | 1 +
2 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 84c04691841f..8595c4f2e915 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2871,7 +2871,6 @@ static void sd_read_app_tag_own(struct scsi_disk *sdkp, unsigned char *buffer)
*/
static void sd_read_block_limits(struct scsi_disk *sdkp)
{
- unsigned int sector_sz = sdkp->device->sector_size;
struct scsi_vpd *vpd;

rcu_read_lock();
@@ -2880,9 +2879,7 @@ static void sd_read_block_limits(struct scsi_disk *sdkp)
if (!vpd || vpd->len < 16)
goto out;

- blk_queue_io_min(sdkp->disk->queue,
- get_unaligned_be16(&vpd->data[6]) * sector_sz);
-
+ sdkp->min_xfer_blocks = get_unaligned_be16(&vpd->data[6]);
sdkp->max_xfer_blocks = get_unaligned_be32(&vpd->data[8]);
sdkp->opt_xfer_blocks = get_unaligned_be32(&vpd->data[12]);

@@ -3140,6 +3137,29 @@ static void sd_read_cpr(struct scsi_disk *sdkp)
kfree(buffer);
}

+static bool sd_validate_min_xfer_size(struct scsi_disk *sdkp)
+{
+ struct scsi_device *sdp = sdkp->device;
+ unsigned int min_xfer_bytes =
+ logical_to_bytes(sdp, sdkp->min_xfer_blocks);
+
+ if (sdkp->min_xfer_blocks == 0)
+ return false;
+
+ if (min_xfer_bytes & (sdkp->physical_block_size - 1)) {
+ sd_first_printk(KERN_WARNING, sdkp,
+ "Preferred minimum I/O size %u bytes not a " \
+ "multiple of physical block size (%u bytes)\n",
+ min_xfer_bytes, sdkp->physical_block_size);
+ sdkp->min_xfer_blocks = 0;
+ return false;
+ }
+
+ sd_first_printk(KERN_INFO, sdkp, "Preferred minimum I/O size %u bytes\n",
+ min_xfer_bytes);
+ return true;
+}
+
/*
* Determine the device's preferred I/O size for reads and writes
* unless the reported value is unreasonably small, large, not a
@@ -3151,6 +3171,8 @@ static bool sd_validate_opt_xfer_size(struct scsi_disk *sdkp,
struct scsi_device *sdp = sdkp->device;
unsigned int opt_xfer_bytes =
logical_to_bytes(sdp, sdkp->opt_xfer_blocks);
+ unsigned int min_xfer_bytes =
+ logical_to_bytes(sdp, sdkp->min_xfer_blocks);

if (sdkp->opt_xfer_blocks == 0)
return false;
@@ -3179,6 +3201,15 @@ static bool sd_validate_opt_xfer_size(struct scsi_disk *sdkp,
return false;
}

+ if (min_xfer_bytes && opt_xfer_bytes & (min_xfer_bytes - 1)) {
+ sd_first_printk(KERN_WARNING, sdkp,
+ "Optimal transfer size %u bytes not a " \
+ "multiple of preferred minimum block " \
+ "size (%u bytes)\n",
+ opt_xfer_bytes, min_xfer_bytes);
+ return false;
+ }
+
if (opt_xfer_bytes & (sdkp->physical_block_size - 1)) {
sd_first_printk(KERN_WARNING, sdkp,
"Optimal transfer size %u bytes not a " \
@@ -3271,6 +3302,12 @@ static int sd_revalidate_disk(struct gendisk *disk)
dev_max = min_not_zero(dev_max, sdkp->max_xfer_blocks);
q->limits.max_dev_sectors = logical_to_sectors(sdp, dev_max);

+ if (sd_validate_min_xfer_size(sdkp))
+ blk_queue_io_min(sdkp->disk->queue,
+ logical_to_bytes(sdp, sdkp->min_xfer_blocks));
+ else
+ blk_queue_io_min(sdkp->disk->queue, 0);
+
if (sd_validate_opt_xfer_size(sdkp, dev_max)) {
q->limits.io_opt = logical_to_bytes(sdp, sdkp->opt_xfer_blocks);
rw_max = logical_to_sectors(sdp, sdkp->opt_xfer_blocks);
diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
index 2e5932bde43d..f4fbca90e997 100644
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -91,6 +91,7 @@ struct scsi_disk {
atomic_t openers;
sector_t capacity; /* size in logical blocks */
int max_retries;
+ u32 min_xfer_blocks;
u32 max_xfer_blocks;
u32 opt_xfer_blocks;
u32 max_ws_blocks;
--
2.32.0