Revert "blockdev: Remove the --setbsz (set blocksize) option which has never worked."

This reverts commit b1555acc2f.

It seems that the option is used by kernel guys to test kernel, so
let's keep the option in the blockdev(8) although it's almost useless
in userspace. All we need is to improve docs to make things more
obvious to end users.

Signed-off-by: Karel Zak <kzak@redhat.com>

bash-completion/blockdev

@@ -19,6 +19,7 @@ _blockdev_module()
 		--getalignoff
 		--getmaxsect
 		--getbsz
+		--setbsz
 		--getsize64
 		--setra
 		--getra
@@ -28,7 +29,11 @@ _blockdev_module()
 		--rereadpt
 		$DEVS"
 	case $prev in
-		'--setfra')
+		'--setbsz')
+			COMPREPLY=( $(compgen -W "bytes" -- $cur) )
+			return 0
+			;;
+		'--setbsz'|'--setfra')
 			COMPREPLY=( $(compgen -W "sectors" -- $cur) )
 			return 0
 			;;

disk-utils/blockdev.8

@@ -67,6 +67,8 @@ Print sectorsize in bytes - usually 512.
 Get size in 512-byte sectors.
 .IP "\fB\-\-rereadpt\fP"
 Reread partition table
+.IP "\fB\-\-setbsz\fP \fIbytes\fP"
+Set blocksize.
 .IP "\fB\-\-setfra\fP \fIsectors\fP"
 Set filesystem readahead (same like --setra on 2.6 kernels).
 .IP "\fB\-\-setra\fP \fIsectors\fP"

disk-utils/blockdev.c

@@ -121,6 +121,13 @@ static const struct bdc bdcms[] =
 		.argtype = ARG_INT,
 		.argval = -1,
 		.help = N_("get blocksize")
+	},{
+		IOCTL_ENTRY(BLKBSZSET),
+		.name = "--setbsz",
+		.argname = "<bytes>",
+		.argtype = ARG_INT,
+		.flags = FL_NORESULT,
+	        .help = N_("set blocksize")
 	},{
 		IOCTL_ENTRY(BLKGETSIZE),
 		.name = "--getsize",