scsi_debug: rework resp_report_luns

Based on "[PATH V2] scsi_debug: rework resp_report_luns" patch
sent by Tomas Winkler on Thursday, 26 Feb 2015. His notes:
  1. Remove duplicated boundary checks which simplify the fill-in
     loop
  2. Use more of scsi generic API
Replace fixed length response array a with heap allocation
allowing up to 256 normal LUNs per target.

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Reviewed-by: Tomas Winkler <tomas.winkler@intel.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index fc0246c..e97ddf0 100644 (file)
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -3208,63 +3208,94 @@ static int resp_get_lba_status(struct scsi_cmnd *scp,
        return fill_from_dev_buffer(scp, arr, SDEBUG_GET_LBA_STATUS_LEN);
 }
 
-#define SDEBUG_RLUN_ARR_SZ 256
-
-static int resp_report_luns(struct scsi_cmnd * scp,
-                           struct sdebug_dev_info * devip)
+/* Even though each pseudo target has a REPORT LUNS "well known logical unit"
+ * (W-LUN), the normal Linux scanning logic does not associate it with a
+ * device (e.g. /dev/sg7). The following magic will make that association:
+ *   "cd /sys/class/scsi_host/host<n> ; echo '- - 49409' > scan"
+ * where <n> is a host number. If there are multiple targets in a host then
+ * the above will associate a W-LUN to each target. To only get a W-LUN
+ * for target 2, then use "echo '- 2 49409' > scan" .
+ */
+static int resp_report_luns(struct scsi_cmnd *scp,
+                           struct sdebug_dev_info *devip)
 {
+       unsigned char *cmd = scp->cmnd;
        unsigned int alloc_len;
-       int lun_cnt, i, upper, num, n, want_wlun, shortish;
+       unsigned char select_report;
        u64 lun;
-       unsigned char *cmd = scp->cmnd;
-       int select_report = (int)cmd[2];
-       struct scsi_lun *one_lun;
-       unsigned char arr[SDEBUG_RLUN_ARR_SZ];
-       unsigned char * max_addr;
+       struct scsi_lun *lun_p;
+       u8 *arr;
+       unsigned int lun_cnt;   /* normal LUN count (max: 256) */
+       unsigned int wlun_cnt;  /* report luns W-LUN count */
+       unsigned int tlun_cnt;  /* total LUN count */
+       unsigned int rlen;      /* response length (in bytes) */
+       int i, res;
 
        clear_luns_changed_on_target(devip);
-       alloc_len = cmd[9] + (cmd[8] << 8) + (cmd[7] << 16) + (cmd[6] << 24);
-       shortish = (alloc_len < 4);
-       if (shortish || (select_report > 2)) {
-               mk_sense_invalid_fld(scp, SDEB_IN_CDB, shortish ? 6 : 2, -1);
+
+       select_report = cmd[2];
+       alloc_len = get_unaligned_be32(cmd + 6);
+
+       if (alloc_len < 4) {
+               pr_err("alloc len too small %d\n", alloc_len);
+               mk_sense_invalid_fld(scp, SDEB_IN_CDB, 6, -1);
                return check_condition_result;
        }
-       /* can produce response with up to 16k luns (lun 0 to lun 16383) */
-       memset(arr, 0, SDEBUG_RLUN_ARR_SZ);
-       lun_cnt = sdebug_max_luns;
-       if (1 == select_report)
+
+       switch (select_report) {
+       case 0:         /* all LUNs apart from W-LUNs */
+               lun_cnt = sdebug_max_luns;
+               wlun_cnt = 0;
+               break;
+       case 1:         /* only W-LUNs */
                lun_cnt = 0;
-       else if (sdebug_no_lun_0 && (lun_cnt > 0))
+               wlun_cnt = 1;
+               break;
+       case 2:         /* all LUNs */
+               lun_cnt = sdebug_max_luns;
+               wlun_cnt = 1;
+               break;
+       case 0x10:      /* only administrative LUs */
+       case 0x11:      /* see SPC-5 */
+       case 0x12:      /* only subsiduary LUs owned by referenced LU */
+       default:
+               pr_debug("select report invalid %d\n", select_report);
+               mk_sense_invalid_fld(scp, SDEB_IN_CDB, 2, -1);
+               return check_condition_result;
+       }
+
+       if (sdebug_no_lun_0 && (lun_cnt > 0))
                --lun_cnt;
-       want_wlun = (select_report > 0) ? 1 : 0;
-       num = lun_cnt + want_wlun;
-       arr[2] = ((sizeof(struct scsi_lun) * num) >> 8) & 0xff;
-       arr[3] = (sizeof(struct scsi_lun) * num) & 0xff;
-       n = min((int)((SDEBUG_RLUN_ARR_SZ - 8) /
-                           sizeof(struct scsi_lun)), num);
-       if (n < num) {
-               want_wlun = 0;
-               lun_cnt = n;
-       }
-       one_lun = (struct scsi_lun *) &arr[8];
-       max_addr = arr + SDEBUG_RLUN_ARR_SZ;
-       for (i = 0, lun = (sdebug_no_lun_0 ? 1 : 0);
-             ((i < lun_cnt) && ((unsigned char *)(one_lun + i) < max_addr));
-            i++, lun++) {
-               upper = (lun >> 8) & 0x3f;
-               if (upper)
-                       one_lun[i].scsi_lun[0] =
-                           (upper | (SAM2_LUN_ADDRESS_METHOD << 6));
-               one_lun[i].scsi_lun[1] = lun & 0xff;
-       }
-       if (want_wlun) {
-               one_lun[i].scsi_lun[0] = (SCSI_W_LUN_REPORT_LUNS >> 8) & 0xff;
-               one_lun[i].scsi_lun[1] = SCSI_W_LUN_REPORT_LUNS & 0xff;
-               i++;
-       }
-       alloc_len = (unsigned char *)(one_lun + i) - arr;
-       return fill_from_dev_buffer(scp, arr,
-                                   min((int)alloc_len, SDEBUG_RLUN_ARR_SZ));
+
+       tlun_cnt = lun_cnt + wlun_cnt;
+
+       rlen = (tlun_cnt * sizeof(struct scsi_lun)) + 8;
+       arr = vmalloc(rlen);
+       if (!arr) {
+               mk_sense_buffer(scp, ILLEGAL_REQUEST, INSUFF_RES_ASC,
+                               INSUFF_RES_ASCQ);
+               return check_condition_result;
+       }
+       memset(arr, 0, rlen);
+       pr_debug("select_report %d luns = %d wluns = %d no_lun0 %d\n",
+                select_report, lun_cnt, wlun_cnt, sdebug_no_lun_0);
+
+       /* luns start at byte 8 in response following the header */
+       lun_p = (struct scsi_lun *)&arr[8];
+
+       /* LUNs use single level peripheral device addressing method */
+       lun = sdebug_no_lun_0 ? 1 : 0;
+       for (i = 0; i < lun_cnt; i++)
+               int_to_scsilun(lun++, lun_p++);
+
+       if (wlun_cnt)
+               int_to_scsilun(SCSI_W_LUN_REPORT_LUNS, lun_p++);
+
+       put_unaligned_be32(rlen - 8, &arr[0]);
+
+       res = fill_from_dev_buffer(scp, arr, rlen);
+       vfree(arr);
+       return res;
 }
 
 static int resp_xdwriteread(struct scsi_cmnd *scp, unsigned long long lba,
@@ -4303,6 +4334,10 @@ static ssize_t max_luns_store(struct device_driver *ddp, const char *buf,
        bool changed;
 
        if ((count > 0) && (1 == sscanf(buf, "%d", &n)) && (n >= 0)) {
+               if (n > 256) {
+                       pr_warn("max_luns can be no more than 256\n");
+                       return -EINVAL;
+               }
                changed = (sdebug_max_luns != n);
                sdebug_max_luns = n;
                sdebug_max_tgts_luns();
@@ -4647,6 +4682,10 @@ static int __init scsi_debug_init(void)
                pr_err("invalid physblk_exp %u\n", sdebug_physblk_exp);
                return -EINVAL;
        }
+       if (sdebug_max_luns > 256) {
+               pr_warn("max_luns can be no more than 256, use default\n");
+               sdebug_max_luns = DEF_MAX_LUNS;
+       }
 
        if (sdebug_lowest_aligned > 0x3fff) {
                pr_err("lowest_aligned too big: %u\n", sdebug_lowest_aligned);