Add a berase() function which uses ioctl(DIOCGDELETE) to erase a slab

of the disk.

lib/libufs/Makefile

@@ -8,6 +8,7 @@ INCS=	libufs.h
 
 MAN=	bread.3 cgread.3 libufs.3 sbread.3 ufs_disk_close.3
 MLINKS+= bread.3 bwrite.3
+MLINKS+= bread.3 berase.3
 MLINKS+= cgread.3 cgread1.3
 MLINKS+= cgread.3 cgwrite1.3
 MLINKS+= sbread.3 sbwrite.3

lib/libufs/block.c

@@ -30,6 +30,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/mount.h>
+#include <sys/disk.h>
 #include <sys/disklabel.h>
 #include <sys/stat.h>
 
@@ -133,3 +134,21 @@ bwrite(struct uufsd *disk, ufs2_daddr_t blockno, const void *data, size_t size)
 
 	return (cnt);
 }
+
+int
+berase(struct uufsd *disk, ufs2_daddr_t blockno, ufs2_daddr_t size)
+{
+	off_t ioarg[2];
+	int rv;
+
+	ERROR(disk, NULL);
+	rv = ufs_disk_write(disk);
+	if (rv == -1) {
+		ERROR(disk, "failed to open disk for writing");
+		return(rv);
+	}
+	ioarg[0] = blockno * disk->d_bsize;
+	ioarg[1] = size;
+	rv = ioctl(disk->d_fd, DIOCGDELETE, ioarg);
+	return (rv);
+}

lib/libufs/bread.3

@@ -31,12 +31,17 @@
 .Fa "struct uufsd *disk" "ufs2_daddr_t blockno"
 .Fa "const void *data" "size_t size"
 .Fc
+.Ft int
+.Fo berase
+.Fa "struct uufsd *disk" "ufs2_daddr_t blockno" "ufs2_daddr_t size"
+.Fc
 .Sh DESCRIPTION
 The
-.Fn bread
-and
+.Fn bread ,
 .Fn bwrite
-functions provide a block read and write API for
+and
+.Fn berase
+functions provide a block read, write and erase API for
 .Xr libufs 3
 consumers.
 They operate on a userland UFS disk structure, and perform the read
@@ -50,6 +55,10 @@ and
 .Fn bwrite
 functions return the amount read or written, or \-1 in case of any error,
 including short read.
+.Pp
+The
+.Fn berase
+function returns non-zero on error.
 .Sh ERRORS
 The function
 .Fn bread
@@ -59,10 +68,6 @@ for any of the errors specified for the library functions
 .Xr ufs_disk_write 3
 or
 .Xr pread 2 .
-Additionally, it may follow the
-.Xr libufs 3
-error methodologies in situations where the amount of data read
-is not equal to the amount requested, or in case of device error.
 .Pp
 The function
 .Fn bwrite
@@ -70,7 +75,15 @@ may fail and set
 .Va errno
 for any of the errors specified for the library function
 .Xr pwrite 2 .
-Additionally, it may follow the
+.Pp
+The function
+.Fn berase
+may fail and set
+.Va errno
+for any of the errors specified for the library function
+.Xr ioctl 2 .
+.Pp
+Additionally all three functions may follow the
 .Xr libufs 3
 error methodologies in situations where the amount of data written
 is not equal to the amount requested, or in case of a device error.

lib/libufs/libufs.h

@@ -104,6 +104,7 @@ __BEGIN_DECLS
  */
 ssize_t bread(struct uufsd *, ufs2_daddr_t, void *, size_t);
 ssize_t bwrite(struct uufsd *, ufs2_daddr_t, const void *, size_t);
+int berase(struct uufsd *, ufs2_daddr_t, ufs2_daddr_t);
 
 /*
  * cgroup.c