scsi: sd: Optimal I/O size should be a multiple of physical block size

It was reported that some devices report an OPTIMAL TRANSFER LENGTH of
0xFFFF blocks. That looks bogus, especially for a device with a
4096-byte physical block size.

Ignore OPTIMAL TRANSFER LENGTH if it is not a multiple of the device's
reported physical block size.

To make the sanity checking conditionals more readable--and to
facilitate printing warnings--relocate the checking to a helper
function. No functional change aside from the printks.

Cc: <stable@vger.kernel.org>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199759
Reported-by: Christoph Anton Mitterer <calestyo@scientia.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index cc175b7..f3e5e6b 100644 (file)
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3061,6 +3061,55 @@ static void sd_read_security(struct scsi_disk *sdkp, unsigned char *buffer)
                sdkp->security = 1;
 }
 
+/*
+ * Determine the device's preferred I/O size for reads and writes
+ * unless the reported value is unreasonably small, large, not a
+ * multiple of the physical block size, or simply garbage.
+ */
+static bool sd_validate_opt_xfer_size(struct scsi_disk *sdkp,
+                                     unsigned int dev_max)
+{
+       struct scsi_device *sdp = sdkp->device;
+       unsigned int opt_xfer_bytes =
+               logical_to_bytes(sdp, sdkp->opt_xfer_blocks);
+
+       if (sdkp->opt_xfer_blocks > dev_max) {
+               sd_first_printk(KERN_WARNING, sdkp,
+                               "Optimal transfer size %u logical blocks " \
+                               "> dev_max (%u logical blocks)\n",
+                               sdkp->opt_xfer_blocks, dev_max);
+               return false;
+       }
+
+       if (sdkp->opt_xfer_blocks > SD_DEF_XFER_BLOCKS) {
+               sd_first_printk(KERN_WARNING, sdkp,
+                               "Optimal transfer size %u logical blocks " \
+                               "> sd driver limit (%u logical blocks)\n",
+                               sdkp->opt_xfer_blocks, SD_DEF_XFER_BLOCKS);
+               return false;
+       }
+
+       if (opt_xfer_bytes < PAGE_SIZE) {
+               sd_first_printk(KERN_WARNING, sdkp,
+                               "Optimal transfer size %u bytes < " \
+                               "PAGE_SIZE (%u bytes)\n",
+                               opt_xfer_bytes, (unsigned int)PAGE_SIZE);
+               return false;
+       }
+
+       if (opt_xfer_bytes & (sdkp->physical_block_size - 1)) {
+               sd_first_printk(KERN_WARNING, sdkp,
+                               "Optimal transfer size %u bytes not a " \
+                               "multiple of physical block size (%u bytes)\n",
+                               opt_xfer_bytes, sdkp->physical_block_size);
+               return false;
+       }
+
+       sd_first_printk(KERN_INFO, sdkp, "Optimal transfer size %u bytes\n",
+                       opt_xfer_bytes);
+       return true;
+}
+
 /**
  *     sd_revalidate_disk - called the first time a new disk is seen,
  *     performs disk spin up, read_capacity, etc.
@@ -3130,15 +3179,7 @@ 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);
 
-       /*
-        * Determine the device's preferred I/O size for reads and writes
-        * unless the reported value is unreasonably small, large, or
-        * garbage.
-        */
-       if (sdkp->opt_xfer_blocks &&
-           sdkp->opt_xfer_blocks <= dev_max &&
-           sdkp->opt_xfer_blocks <= SD_DEF_XFER_BLOCKS &&
-           logical_to_bytes(sdp, sdkp->opt_xfer_blocks) >= PAGE_SIZE) {
+       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);
        } else