Re: bin/51619

On Wed, 7 May 2003, Kirk McKusick wrote:

> At one time I had the suggested change that you made in bin/51619
> in the FreeBSD-5.0 newfs program. The problem with that change is
> that the bootstrap on some architectures now exceeds 8K which means
> that instead of zeroing an old superblock you destroy the boot code.
> So, I removed the zeroing of the old UFS1 superblock area. A possible
> alternative would be to check for a UFS1 magic number at the old
> location (and also at the 16K first backup location) and zero out
> just those fields if they are found. While it is possible that a
> bootstrap might just have that number at that offset, it is highly
> unlikely.

Hi Kirk,

thanks for clarifying this. Would this patch here be better suited?

---8<---
Index: sbin/newfs/mkfs.c
===================================================================
RCS file: /u/cvs/cvs/src/sbin/newfs/mkfs.c,v
retrieving revision 1.75
diff -u -r1.75 mkfs.c
--- sbin/newfs/mkfs.c	3 May 2003 18:41:58 -0000	1.75
+++ sbin/newfs/mkfs.c	8 May 2003 10:42:15 -0000
_at__at_ -113,6 +113,12 _at__at_
 	quad_t sizepb;
 	int width;
 	char tmpbuf[100];	/* XXX this will break in about 2,500 years */
+	union {
+		struct fs fdummy;
+		char cdummy[SBLOCKSIZE];
+	} dummy;
+#define fsdummy dummy.fdummy
+#define chdummy dummy.cdummy

 	/*
 	 * Our blocks == sector size, and the version of UFS we are using is
_at__at_ -479,8 +485,22 _at__at_
 		sblock.fs_old_cstotal.cs_nifree = sblock.fs_cstotal.cs_nifree;
 		sblock.fs_old_cstotal.cs_nffree = sblock.fs_cstotal.cs_nffree;
 	}
-	if (!Nflag)
+	if (!Nflag) {
+		/*
+		 * Wipe out old UFS1 superblock if necessary.
+		 */
+		if (Oflag != 1) {
+			i = bread(&disk, SBLOCK_UFS1 / disk.d_bsize, chdummy, SBLOCKSIZE);
+			if (i == -1)
+				err(1, "can't bread: %s", disk.d_error);
+
+			if (fsdummy.fs_magic == FS_UFS1_MAGIC) {
+				fsdummy.fs_magic = 0;
+				bwrite(&disk, SBLOCK_UFS1 / disk.d_bsize, chdummy, SBLOCKSIZE);
+			}
+		}
 		sbwrite(&disk, 0);
+	}
 	for (i = 0; i < sblock.fs_cssize; i += sblock.fs_bsize)
 		wtfs(fsbtodb(&sblock, sblock.fs_csaddr + numfrags(&sblock, i)),
 			sblock.fs_cssize - i < sblock.fs_bsize ?
---8<---

regards,
le

-- 
Lukas Ertl                             eMail: l.ertl_at_univie.ac.at
UNIX-Systemadministrator               Tel.:  (+43 1) 4277-14073
Zentraler Informatikdienst (ZID)       Fax.:  (+43 1) 4277-9140
der Universität Wien                   http://mailbox.univie.ac.at/~le/