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From: Colin Percival <cperciva@FreeBSD.org>
Date: Tue, 26 Apr 2011 02:06:31 +0000 (UTC)
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Subject: svn commit: r221049 - head/sbin/newfs
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Author: cperciva
Date: Tue Apr 26 02:06:31 2011
New Revision: 221049
URL: http://svn.freebsd.org/changeset/base/221049

Log:
  Stop trying to zero UFS1 superblocks if we fall off the end of the disk.
  
  This avoids a potentially many-hours-long loop of failed writes if newfs
  finds a partially-overwritten superblock (or, for that matter, random
  garbage which happens to have superblock magic bytes); on one occasion I
  found newfs trying to zero 800 million superblocks on a 50 MB disk.
  
  Reviewed by:	mckusick
  MFC after:	1 week

Modified:
  head/sbin/newfs/mkfs.c

Modified: head/sbin/newfs/mkfs.c
==============================================================================
--- head/sbin/newfs/mkfs.c	Tue Apr 26 01:56:18 2011	(r221048)
+++ head/sbin/newfs/mkfs.c	Tue Apr 26 02:06:31 2011	(r221049)
@@ -516,9 +516,12 @@ restart:
 			fsdummy.fs_magic = 0;
 			bwrite(&disk, part_ofs + SBLOCK_UFS1 / disk.d_bsize,
 			    chdummy, SBLOCKSIZE);
-			for (cg = 0; cg < fsdummy.fs_ncg; cg++)
+			for (cg = 0; cg < fsdummy.fs_ncg; cg++) {
+				if (fsbtodb(&fsdummy, cgsblock(&fsdummy, cg)) > fssize)
+					break;
 				bwrite(&disk, part_ofs + fsbtodb(&fsdummy,
 				  cgsblock(&fsdummy, cg)), chdummy, SBLOCKSIZE);
+			}
 		}
 	}
 	if (!Nflag)