Implement cgwrite1(3) function which stored a given cylinder group on disk.

Sponsored by:	home.pl

lib/libufs/Makefile

@@ -9,6 +9,7 @@ INCS=	libufs.h
 MAN=	bread.3 cgread.3 libufs.3 sbread.3 ufs_disk_close.3
 MLINKS+= bread.3 bwrite.3
 MLINKS+= cgread.3 cgread1.3
+MLINKS+= cgread.3 cgwrite1.3
 MLINKS+= sbread.3 sbwrite.3
 MLINKS+= ufs_disk_close.3 ufs_disk_fillout.3
 MLINKS+= ufs_disk_close.3 ufs_disk_fillout_blank.3

lib/libufs/cgread.3

@@ -4,6 +4,7 @@
 .\" 	Manual page for libufs functions:
 .\"		cgread(3)
 .\"		cgread1(3)
+.\"		cgwrite1(3)
 .\"
 .\" This file is in the public domain.
 .\"
@@ -13,8 +14,8 @@
 .Dt CGREAD 3
 .Os
 .Sh NAME
-.Nm cgread , cgread1
-.Nd read cylinder groups of UFS disks
+.Nm cgread , cgread1, cgwrite1
+.Nd read/write cylinder groups of UFS disks
 .Sh LIBRARY
 .Lb libufs
 .Sh SYNOPSIS
@@ -28,6 +29,8 @@
 .Fn cgread "struct uufsd *disk"
 .Ft int
 .Fn cgread1 "struct uufsd *disk" "int c"
+.Ft int
+.Fn cgwrite1 "struct uufsd *disk" "int c"
 .Sh DESCRIPTION
 The
 .Fn cgread
@@ -60,6 +63,14 @@ with a cylinder group specifier equivalent to the value of the current
 field, and then incrementing the
 .Va d_ccg
 field.
+.Pp
+The
+.Fn cgwrite1
+function stores cylinder group specified by
+.Fa c
+from
+.Va d_cg
+field of a userland UFS disk structure on disk.
 .Sh RETURN VALUES
 Both functions return 0 if there are no more cylinder groups to read,
 1 if there are more cylinder groups, and \-1 on error.
@@ -75,8 +86,16 @@ The function
 .Fn cgread1
 has semantically identical failure conditions to those of
 .Fn cgread .
+.Pp
+The function
+.Fn cgwrite1
+may fail and set
+.Va errno
+for any of the errors specified for the library function
+.Xr bwrite 3 .
 .Sh SEE ALSO
 .Xr bread 3 ,
+.Xr bwrite 3 ,
 .Xr libufs 3
 .Sh HISTORY
 These functions first appeared as part of

lib/libufs/cgroup.c

@@ -71,3 +71,17 @@ cgread1(struct uufsd *disk, int c)
 	disk->d_lcg = c;
 	return (1);
 }
+
+int
+cgwrite1(struct uufsd *disk, int c)
+{
+	struct fs *fs;
+
+	fs = &disk->d_fs;
+	if (bwrite(disk, fsbtodb(fs, cgtod(fs, c)),
+	    disk->d_cgunion.d_buf, fs->fs_bsize) == -1) {
+		ERROR(disk, "unable to write cylinder group");
+		return (-1);
+	}
+	return (0);
+}

lib/libufs/libufs.3

@@ -57,6 +57,7 @@ to a string describing the error.
 .Xr bwrite 3 ,
 .Xr cgread 3 ,
 .Xr cgread1 3 ,
+.Xr cgwrite1 3 ,
 .Xr sbread 3 ,
 .Xr sbwrite 3 ,
 .Xr ufs_disk_close 3 ,

lib/libufs/libufs.h

@@ -110,6 +110,7 @@ ssize_t bwrite(struct uufsd *, ufs2_daddr_t, const void *, size_t);
  */
 int cgread(struct uufsd *);
 int cgread1(struct uufsd *, int);
+int cgwrite1(struct uufsd *, int);
 
 /*
  * inode.c