Enable operation of newfs on plain files, which is useful when you

want to prepare disk images for emulators (though 'makefs' in port
can do something similar).

This relies on:
+ minor changes to pass the consistency checks even when working on a file;

+ an additional option, '-p partition' , to specify the disk partition to
  initialize;

+ some changes on the I/O routines to deal with partition offsets.

The latter was a bit tricky to implement, see the details in newfs.h:
in newfs, I/O is done through libufs which assumes that the file
descriptor refers to the whole partition. Introducing support for
the offset in libufs would require a non-backward compatible change
in the library, to be dealt with a version bump or with symbol
versioning.

I felt both approaches to be overkill for this specific application,
especially because there might be other changes to libufs that might
become necessary in the near future.

So I used the following trick:
- read access is always done by calling bread() directly, so we just add
  the offset in the (few) places that call bread();
- write access is done through bwrite() and sbwrite(), which in turn
  calls bwrite(). To avoid rewriting sbwrite(), we supply our own version
  of bwrite() here, which takes precedence over the version in libufs.

MFC after:	4 weeks

1 files changed, 4 insertions, 4 deletions

diff --git a/sbin/newfs/mkfs.c b/sbin/newfs/mkfs.c
index b3bbcbf..072e528 100644
--- a/sbin/newfs/mkfs.c
+++ b/sbin/newfs/mkfs.c
@@ -459,7 +459,7 @@ mkfs(struct partition *pp, char *fsys)
 	 * Wipe out old UFS1 superblock(s) if necessary.
 	 */
 	if (!Nflag && Oflag != 1) {
-		i = bread(&disk, SBLOCK_UFS1 / disk.d_bsize, chdummy, SBLOCKSIZE);
+		i = bread(&disk, part_ofs + SBLOCK_UFS1 / disk.d_bsize, chdummy, SBLOCKSIZE);
 		if (i == -1)
 			err(1, "can't read old UFS1 superblock: %s", disk.d_error);
 
@@ -872,7 +872,7 @@ alloc(int size, int mode)
 {
 	int i, d, blkno, frag;
 
-	bread(&disk, fsbtodb(&sblock, cgtod(&sblock, 0)), (char *)&acg,
+	bread(&disk, part_ofs + fsbtodb(&sblock, cgtod(&sblock, 0)), (char *)&acg,
 	    sblock.fs_cgsize);
 	if (acg.cg_magic != CG_MAGIC) {
 		printf("cg 0: bad magic number\n");
@@ -925,7 +925,7 @@ iput(union dinode *ip, ino_t ino)
 	int c;
 
 	c = ino_to_cg(&sblock, ino);
-	bread(&disk, fsbtodb(&sblock, cgtod(&sblock, 0)), (char *)&acg,
+	bread(&disk, part_ofs + fsbtodb(&sblock, cgtod(&sblock, 0)), (char *)&acg,
 	    sblock.fs_cgsize);
 	if (acg.cg_magic != CG_MAGIC) {
 		printf("cg 0: bad magic number\n");
@@ -942,7 +942,7 @@ iput(union dinode *ip, ino_t ino)
 		exit(32);
 	}
 	d = fsbtodb(&sblock, ino_to_fsba(&sblock, ino));
-	bread(&disk, d, (char *)iobuf, sblock.fs_bsize);
+	bread(&disk, part_ofs + d, (char *)iobuf, sblock.fs_bsize);
 	if (sblock.fs_magic == FS_UFS1_MAGIC)
 		((struct ufs1_dinode *)iobuf)[ino_to_fsbo(&sblock, ino)] =
 		    ip->dp1;