[PATCH 2/4] partx: add BLKPG_RES_PARTITION support

[PATCH 2/4] partx: add BLKPG_RES_PARTITION support

[Phillip Susi]

Add new respart shell command and enhance partx update command to use
BLKPG_RES_PARTITION to resize an existing partition while it is in use.

Signed-off-by: Phillip Susi <psusi@cfl.rr.com>
---
 partx/Makefile.am |    4 ++--
 partx/partx.c     |    9 +++++++++
 partx/partx.h     |   19 +++++++++++++++++++
 partx/respart.8   |   46 ++++++++++++++++++++++++++++++++++++++++++++++
 partx/respart.c   |   31 +++++++++++++++++++++++++++++++
 5 files changed, 107 insertions(+), 2 deletions(-)
 create mode 100644 partx/respart.8
 create mode 100644 partx/respart.c

diff --git a/partx/Makefile.am b/partx/Makefile.am
index 080bc47..ce6fd5a 100644
--- a/partx/Makefile.am
+++ b/partx/Makefile.am
@@ -1,7 +1,7 @@
 include $(top_srcdir)/config/include-Makefile.am
 
-usrsbin_exec_PROGRAMS = addpart delpart
-dist_man_MANS = addpart.8 delpart.8
+usrsbin_exec_PROGRAMS = addpart delpart respart
+dist_man_MANS = addpart.8 delpart.8 respart.8
 
 usrsbin_exec_PROGRAMS += partx
 partx_SOURCES = partx.c partx.h \
diff --git a/partx/partx.c b/partx/partx.c
index 87443c4..2510ffb 100644
--- a/partx/partx.c
+++ b/partx/partx.c
@@ -467,6 +467,15 @@ static int upd_parts(int fd, const char *device, dev_t devno,
 		{
 			if (i < nparts)
 				i++;
+			if (err == -1 && errno == EBUSY)
+			{
+				/* try to resize */
+				err = partx_res_partition(fd, n, start, size);
+				if (verbose)
+					printf(_("%s: partition #%d resized\n"), device, n);
+				if (err == 0)
+					continue;
+			}
 			if (err == 0 && partx_add_partition(fd, n, start, size) == 0) {
 				if (verbose)
 					printf(_("%s: partition #%d added\n"), device, n);
diff --git a/partx/partx.h b/partx/partx.h
index b40fa8f..f85f75b 100644
--- a/partx/partx.h
+++ b/partx/partx.h
@@ -41,4 +41,23 @@ static inline int partx_add_partition(int fd, int partno,
 	return ioctl(fd, BLKPG, &a);
 }
 
+static inline int partx_res_partition(int fd, int partno,
+			unsigned long start, unsigned long size)
+{
+	struct blkpg_ioctl_arg a;
+	struct blkpg_partition p;
+
+	p.pno = partno;
+	p.start = start << 9;
+	p.length = size << 9;
+	p.devname[0] = 0;
+	p.volname[0] = 0;
+	a.op = BLKPG_RES_PARTITION;
+	a.flags = 0;
+	a.datalen = sizeof(p);
+	a.data = &p;
+
+	return ioctl(fd, BLKPG, &a);
+}
+
 #endif /*  UTIL_LINUX_PARTX_H */
diff --git a/partx/respart.8 b/partx/respart.8
new file mode 100644
index 0000000..2bbda0b
--- /dev/null
+++ b/partx/respart.8
@@ -0,0 +1,46 @@
+.\" addpart.8 --
+.\" Copyright 2007 Karel Zak <kzak@redhat.com>
+.\" Copyright 2007 Red Hat, Inc.
+.\" May be distributed under the GNU General Public License
+.TH ADDPART 8 "January 2007" "util-linux" "System Administration"
+.SH NAME
+respart \-
+simple wrapper around the "resize partition" ioctl
+.SH SYNOPSIS
+.B respart
+.I device partition start length
+.SH DESCRIPTION
+.B respart
+is a program that updates the Linux kernel's idea of where a partition
+is.  Currently only the length can be changed; the start location must
+be the same as what the kernel already thinks.  This works even on
+partitions that are mounted.  Most filesystems ( including ext4 )
+can grow online ( see .BR resize2fs ), but not shrink.  Shrinking
+the size of the partition to be less than the filesystem inside it
+will cause data loss.
+
+This command doesn't manipulate partitions on hard drive.
+
+.SH PARAMETERS
+.TP
+.I device
+Specify the disk device.
+.TP
+.I partition
+Specify the partition number.
+.TP
+.I start
+Specify the begin of the partition (in 512-byte sectors).
+.TP
+.I length
+Specify the length of the partition (in 512-byte sectors).
+
+.SH SEE ALSO
+.BR delpart (8),
+.BR fdisk (8),
+.BR parted (8),
+.BR partprobe (8),
+.BR partx (8)
+.SH AVAILABILITY
+The addpart command is part of the util-linux package and is available from
+ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
diff --git a/partx/respart.c b/partx/respart.c
new file mode 100644
index 0000000..27060a8
--- /dev/null
+++ b/partx/respart.c
@@ -0,0 +1,31 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+
+#include "partx.h"
+
+int
+main(int argc, char **argv)
+{
+	int fd;
+
+	if (argc != 5) {
+		fprintf(stderr,
+			"usage: %s diskdevice partitionnr start length\n",
+			argv[0]);
+		exit(1);
+	}
+	if ((fd = open(argv[1], O_RDONLY)) < 0) {
+		perror(argv[1]);
+		exit(1);
+	}
+
+	if (partx_res_partition(fd, atoi(argv[2]),
+				atoll(argv[3]),
+				atoll(argv[4]))) {
+		perror("BLKPG");
+		exit(1);
+	}
+
+	return 0;
+}
-- 
1.7.5.4

Re: [PATCH 2/4] partx: add BLKPG_RES_PARTITION support

[Davidlohr Bueso]

On Mon, 2011-12-05 at 15:02 -0500, Phillip Susi wrote:
> Add new respart shell command and enhance partx update command to use
> BLKPG_RES_PARTITION to resize an existing partition while it is in use.
> 
> Signed-off-by: Phillip Susi <psusi@cfl.rr.com>
> ---
>  partx/Makefile.am |    4 ++--
>  partx/partx.c     |    9 +++++++++
>  partx/partx.h     |   19 +++++++++++++++++++
>  partx/respart.8   |   46 ++++++++++++++++++++++++++++++++++++++++++++++
>  partx/respart.c   |   31 +++++++++++++++++++++++++++++++
>  5 files changed, 107 insertions(+), 2 deletions(-)
>  create mode 100644 partx/respart.8
>  create mode 100644 partx/respart.c
> 
> diff --git a/partx/Makefile.am b/partx/Makefile.am
> index 080bc47..ce6fd5a 100644
> --- a/partx/Makefile.am
> +++ b/partx/Makefile.am
> @@ -1,7 +1,7 @@
>  include $(top_srcdir)/config/include-Makefile.am
>  
> -usrsbin_exec_PROGRAMS = addpart delpart
> -dist_man_MANS = addpart.8 delpart.8
> +usrsbin_exec_PROGRAMS = addpart delpart respart
> +dist_man_MANS = addpart.8 delpart.8 respart.8
>  
>  usrsbin_exec_PROGRAMS += partx
>  partx_SOURCES = partx.c partx.h \
> diff --git a/partx/partx.c b/partx/partx.c
> index 87443c4..2510ffb 100644
> --- a/partx/partx.c
> +++ b/partx/partx.c
> @@ -467,6 +467,15 @@ static int upd_parts(int fd, const char *device, dev_t devno,
>  		{
>  			if (i < nparts)
>  				i++;
> +			if (err == -1 && errno == EBUSY)
> +			{
> +				/* try to resize */
> +				err = partx_res_partition(fd, n, start, size);
> +				if (verbose)
> +					printf(_("%s: partition #%d resized\n"), device, n);
> +				if (err == 0)
> +					continue;
> +			}
>  			if (err == 0 && partx_add_partition(fd, n, start, size) == 0) {
>  				if (verbose)
>  					printf(_("%s: partition #%d added\n"), device, n);
> diff --git a/partx/partx.h b/partx/partx.h
> index b40fa8f..f85f75b 100644
> --- a/partx/partx.h
> +++ b/partx/partx.h
> @@ -41,4 +41,23 @@ static inline int partx_add_partition(int fd, int partno,
>  	return ioctl(fd, BLKPG, &a);
>  }
>  
> +static inline int partx_res_partition(int fd, int partno,
> +			unsigned long start, unsigned long size)
> +{
> +	struct blkpg_ioctl_arg a;
> +	struct blkpg_partition p;
> +
> +	p.pno = partno;
> +	p.start = start << 9;
> +	p.length = size << 9;
> +	p.devname[0] = 0;
> +	p.volname[0] = 0;
> +	a.op = BLKPG_RES_PARTITION;

I like the idea, but we should wait until your BLKPG resize patches are
accepted in mainline before applying here. Also, assuming they make it
into the kernel, this patch would break partx compilation on older
kernels.

- Davidlohr

Re: [PATCH 2/4] partx: add BLKPG_RES_PARTITION support

[Phillip Susi]

On 12/6/2011 1:55 PM, Davidlohr Bueso wrote:
> I like the idea, but we should wait until your BLKPG resize patches are
> accepted in mainline before applying here. Also, assuming they make it
> into the kernel, this patch would break partx compilation on older
> kernels.

Indeed.  I thought that util-linux was closely enough tied to the kernel 
that it didn't care about building on older kernels?  I put #ifdefs 
around the code using it in parted, but didn't think it was needed for 
util-linux.  Easy enough to add them back if you think it's necessary.

Re: [PATCH 2/4] partx: add BLKPG_RES_PARTITION support

[Karel Zak]

On Tue, Dec 06, 2011 at 02:04:37PM -0500, Phillip Susi wrote:
> On 12/6/2011 1:55 PM, Davidlohr Bueso wrote:
>> I like the idea, but we should wait until your BLKPG resize patches are
>> accepted in mainline before applying here. Also, assuming they make it
>> into the kernel, this patch would break partx compilation on older
>> kernels.
>
> Indeed.  I thought that util-linux was closely enough tied to the kernel  
> that it didn't care about building on older kernels?  I put #ifdefs  
> around the code using it in parted, but didn't think it was needed for  
> util-linux.

 The command line (our API) should not depend on kernel features, so
 we usually use fallback definitions (see for example include/blkdev.h) 
 in case that libc/kernel header files are too old.

> Easy enough to add them back if you think it's necessary.

 This is detail ;-) I'll fix it before commit.

 The more important is to have kernel part in Linus' tree...

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com