sd.c: be more cautious in asking for mode page 8 data,

sanity-checking the information more carefully.

The old code basically just used a random-number approach
to determine how much to read.

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 2bd0ee80e138e7da4424beb2a2dd0adf153d95df..08d7cd49ca2bb12b0aae5772bc912cf2303fc29b 100644 (file)
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1108,14 +1108,26 @@ sd_read_cache_type(struct scsi_disk *sdkp, char *diskname,
        /* cautiously ask */
        res = sd_do_mode_sense(SRpnt, dbd, modepage, buffer, 4, &data);
 
-       if (scsi_status_is_good(res)) {
-               /* that went OK, now ask for the proper length */
-               len = data.length;
-               if (len > 128)
-                       len = 128;
-               res = sd_do_mode_sense(SRpnt, dbd, modepage, buffer,
-                                      len, &data);
-       }
+       if (!scsi_status_is_good(res))
+               goto bad_sense;
+
+       /* that went OK, now ask for the proper length */
+       len = data.length;
+
+       /*
+        * We're only interested in the first three bytes, actually.
+        * But the data cache page is defined for the first 20.
+        */
+       if (len < 3)
+               goto bad_sense;
+       if (len > 20)
+               len = 20;
+
+       /* Take headers and block descriptors into account */
+       len += data.header_length + data.block_descriptor_length;
+
+       /* Get the data */
+       res = sd_do_mode_sense(SRpnt, dbd, modepage, buffer, len, &data);
 
        if (scsi_status_is_good(res)) {
                const char *types[] = {
@@ -1133,23 +1145,26 @@ sd_read_cache_type(struct scsi_disk *sdkp, char *diskname,
 
                printk(KERN_NOTICE "SCSI device %s: drive cache: %s\n",
                       diskname, types[ct]);
+
+               return;
+       }
+
+bad_sense:
+       if ((SRpnt->sr_sense_buffer[0] & 0x70) == 0x70
+            && (SRpnt->sr_sense_buffer[2] & 0x0f) == ILLEGAL_REQUEST
+            /* ASC 0x24 ASCQ 0x00: Invalid field in CDB */
+            && SRpnt->sr_sense_buffer[12] == 0x24
+            && SRpnt->sr_sense_buffer[13] == 0x00) {
+               printk(KERN_NOTICE "%s: cache data unavailable\n",
+                      diskname);
        } else {
-               if ((SRpnt->sr_sense_buffer[0] & 0x70) == 0x70
-                    && (SRpnt->sr_sense_buffer[2] & 0x0f) == ILLEGAL_REQUEST
-                    /* ASC 0x24 ASCQ 0x00: Invalid field in CDB */
-                    && SRpnt->sr_sense_buffer[12] == 0x24
-                    && SRpnt->sr_sense_buffer[13] == 0x00) {
-                       printk(KERN_NOTICE "%s: cache data unavailable\n",
-                              diskname);
-               } else {
-                       printk(KERN_ERR "%s: asking for cache data failed\n",
-                              diskname);
-               }
-               printk(KERN_ERR "%s: assuming drive cache: write through\n",
+               printk(KERN_ERR "%s: asking for cache data failed\n",
                       diskname);
-               sdkp->WCE = 0;
-               sdkp->RCD = 0;
        }
+       printk(KERN_ERR "%s: assuming drive cache: write through\n",
+              diskname);
+       sdkp->WCE = 0;
+       sdkp->RCD = 0;
 }
 
 /**