Author: mav
Date: Thu Jun 20 20:29:42 2019
New Revision: 349243
URL: https://svnweb.freebsd.org/changeset/base/349243

Log:
  Optimize xpt_getattr().
  
  Do not allocate temporary buffer for attributes we are going to return
  as-is, just make sure to NUL-terminate them.  Do not zero temporary 64KB
  buffer for CDAI_TYPE_SCSI_DEVID, XPT tells us how much data it filled
  and there are also length fields inside the returned data also.
  
  MFC after:    2 weeks
  Sponsored by: iXsystems, Inc.

Modified:
  head/sys/cam/cam_xpt.c

Modified: head/sys/cam/cam_xpt.c
==============================================================================
--- head/sys/cam/cam_xpt.c      Thu Jun 20 20:06:19 2019        (r349242)
+++ head/sys/cam/cam_xpt.c      Thu Jun 20 20:29:42 2019        (r349243)
@@ -1253,6 +1253,7 @@ xpt_getattr(char *buf, size_t len, const char *attr, s
        cdai.ccb_h.func_code = XPT_DEV_ADVINFO;
        cdai.flags = CDAI_FLAG_NONE;
        cdai.bufsiz = len;
+       cdai.buf = buf;
 
        if (!strcmp(attr, "GEOM::ident"))
                cdai.buftype = CDAI_TYPE_SERIAL_NUM;
@@ -1262,14 +1263,14 @@ xpt_getattr(char *buf, size_t len, const char *attr, s
                 strcmp(attr, "GEOM::lunname") == 0) {
                cdai.buftype = CDAI_TYPE_SCSI_DEVID;
                cdai.bufsiz = CAM_SCSI_DEVID_MAXLEN;
+               cdai.buf = malloc(cdai.bufsiz, M_CAMXPT, M_NOWAIT);
+               if (cdai.buf == NULL) {
+                       ret = ENOMEM;
+                       goto out;
+               }
        } else
                goto out;
 
-       cdai.buf = malloc(cdai.bufsiz, M_CAMXPT, M_NOWAIT|M_ZERO);
-       if (cdai.buf == NULL) {
-               ret = ENOMEM;
-               goto out;
-       }
        xpt_action((union ccb *)&cdai); /* can only be synchronous */
        if ((cdai.ccb_h.status & CAM_DEV_QFRZN) != 0)
                cam_release_devq(cdai.ccb_h.path, 0, 0, 0, FALSE);
@@ -1334,13 +1335,15 @@ xpt_getattr(char *buf, size_t len, const char *attr, s
                                ret = EFAULT;
                }
        } else {
-               ret = 0;
-               if (strlcpy(buf, cdai.buf, len) >= len)
+               if (cdai.provsiz < len) {
+                       cdai.buf[cdai.provsiz] = 0;
+                       ret = 0;
+               } else
                        ret = EFAULT;
        }
 
 out:
-       if (cdai.buf != NULL)
+       if ((char *)cdai.buf != buf)
                free(cdai.buf, M_CAMXPT);
        return ret;
 }
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