nda: AC_GETDEV_CHANGED calls media chanaged for sectorsize change

When the sector size changes, we assume it's new media. When the
mediasize changes, we'll just resize the disk (we get called for both
events). When neither have changed, don't call either.

Some NVMe drives (but not all) post a async event on page 4 with the
sector size changes via a FORMAT command. We'll notice the new media
right away, rather than the next device open. As a practical effect,
this just means that certain geom operations will see it sooner. Since
most drive interaction goes through open, that will catch those drives
that do not post this event well enough.

Sponsored by:		Netflix
Differential Revision:	https://reviews.freebsd.org/D55521

sys/cam/nvme/nvme_da.c

@@ -432,7 +432,7 @@ ndaclose(struct disk *dp)
 	    ("nda %d outstanding commands", softc->outstanding_cmds));
 	cam_periph_unlock(periph);
 	cam_periph_release(periph);
-	return (0);	
+	return (0);
 }
 
 static void
@@ -760,17 +760,23 @@ ndaasync(void *callback_arg, uint32_t code, struct cam_path *path, void *arg)
 	}
 	case AC_GETDEV_CHANGED:
 	{
-		int error;
+		off_t mediasize;
+		u_int sectorsize;
 
 		softc = periph->softc;
+		mediasize = softc->disk->d_mediasize;
+		sectorsize = softc->disk->d_sectorsize;
 		ndasetgeom(softc, periph);
-		error = disk_resize(softc->disk, M_NOWAIT);
-		if (error != 0) {
-			xpt_print(periph->path, "disk_resize(9) failed, error = %d\n", error);
-			break;
-		}
+		/*
+		 * If the sectorsize changed, then it's new media. Otherwise if
+		 * the media size changed, resize the existing disk. Otherwise
+		 * do nothing.
+		 */
+		if (sectorsize != softc->disk->d_sectorsize)
+			disk_media_changed(softc->disk, M_WAITOK);
+		else if (mediasize != softc->disk->d_mediasize)
+			disk_resize(softc->disk, M_WAITOK);
 		break;
-
 	}
 	case AC_ADVINFO_CHANGED:
 	{