WSL2-Linux-Kernel/drivers/block
J. R. Okajima 53d6660836 loop: add ioctl to resize a loop device
Add the ability to 'resize' the loop device on the fly.

One practical application is a loop file with XFS filesystem, already
mounted: You can easily enlarge the file (append some bytes) and then call
ioctl(fd, LOOP_SET_CAPACITY, new); The loop driver will learn about the
new size and you can use xfs_growfs later on, which will allow you to use
full capacity of the loop file without the need to unmount.

Test app:

#include <linux/fs.h>
#include <linux/loop.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define _GNU_SOURCE
#include <getopt.h>

char *me;

void usage(FILE *f)
{
	fprintf(f, "%s [options] loop_dev [backend_file]\n"
		"-s, --set new_size_in_bytes\n"
		"\twhen backend_file is given, "
		"it will be expanded too while keeping the original contents\n",
		me);
}

struct option opts[] = {
	{
		.name		= "set",
		.has_arg	= 1,
		.flag		= NULL,
		.val		= 's'
	},
	{
		.name		= "help",
		.has_arg	= 0,
		.flag		= NULL,
		.val		= 'h'
	}
};

void err_size(char *name, __u64 old)
{
	fprintf(stderr, "size must be larger than current %s (%llu)\n",
		name, old);
}

int main(int argc, char *argv[])
{
	int fd, err, c, i, bfd;
	ssize_t ssz;
	size_t sz;
	__u64 old, new, append;
	char a[BUFSIZ];
	struct stat st;
	FILE *out;
	char *backend, *dev;

	err = EINVAL;
	out = stderr;
	me = argv[0];
	new = 0;
	while ((c = getopt_long(argc, argv, "s:h", opts, &i)) != -1) {
		switch (c) {
		case 's':
			errno = 0;
			new = strtoull(optarg, NULL, 0);
			if (errno) {
				err = errno;
				perror(argv[i]);
				goto out;
			}
			break;

		case 'h':
			err = 0;
			out = stdout;
			goto err;

		default:
			perror(argv[i]);
			goto err;
		}
	}

	if (optind < argc)
		dev = argv[optind++];
	else
		goto err;

	fd = open(dev, O_RDONLY);
	if (fd < 0) {
		err = errno;
		perror(dev);
		goto out;
	}

	err = ioctl(fd, BLKGETSIZE64, &old);
	if (err) {
		err = errno;
		perror("ioctl BLKGETSIZE64");
		goto out;
	}

	if (!new) {
		printf("%llu\n", old);
		goto out;
	}

	if (new < old) {
		err = EINVAL;
		err_size(dev, old);
		goto out;
	}

	if (optind < argc) {
		backend = argv[optind++];
		bfd = open(backend, O_WRONLY|O_APPEND);
		if (bfd < 0) {
			err = errno;
			perror(backend);
			goto out;
		}
		err = fstat(bfd, &st);
		if (err) {
			err = errno;
			perror(backend);
			goto out;
		}
		if (new < st.st_size) {
			err = EINVAL;
			err_size(backend, st.st_size);
			goto out;
		}
		append = new - st.st_size;
		sz = sizeof(a);
		while (append > 0) {
			if (append < sz)
				sz = append;
			ssz = write(bfd, a, sz);
			if (ssz != sz) {
				err = errno;
				perror(backend);
				goto out;
			}
			append -= sz;
		}
		err = fsync(bfd);
		if (err) {
			err = errno;
			perror(backend);
			goto out;
		}
	}

	err = ioctl(fd, LOOP_SET_CAPACITY, new);
	if (err) {
		err = errno;
		perror("ioctl LOOP_SET_CAPACITY");
	}
	goto out;

 err:
	usage(out);
 out:
	return err;
}

Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
Signed-off-by: Tomas Matejicek <tomas@slax.org>
Cc: <util-linux-ng@vger.kernel.org>
Cc: Karel Zak <kzak@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: <linux-api@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-01 08:59:17 -07:00
..
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paride paride/pg.c: xs(): &&/|| confusion 2009-02-18 10:32:01 +01:00
DAC960.c [PATCH] switch DAC960 2008-10-21 07:47:36 -04:00
DAC960.h Fix DAC960 driver on machines which don't support 64-bit DMA 2007-09-11 17:21:19 -07:00
Kconfig m68k: mac - Add SWIM floppy support 2009-03-26 21:15:27 +01:00
Makefile m68k: mac - Add SWIM floppy support 2009-03-26 21:15:27 +01:00
amiflop.c m68k: amiflop - Get rid of sleep_on calls 2009-01-12 20:56:33 +01:00
ataflop.c m68k: atari - Rename "mfp" to "st_mfp" 2009-02-22 09:23:02 -08:00
brd.c [PATCH] switch brd 2008-10-21 07:47:44 -04:00
cciss.c cciss: add BUILD_BUG_ON() for catching bad CommandList_struct alignment 2009-03-24 12:35:16 +01:00
cciss.h cciss: switch to using hlist for command list management 2008-12-29 08:28:43 +01:00
cciss_cmd.h cciss: switch to using hlist for command list management 2008-12-29 08:28:43 +01:00
cciss_scsi.c cciss: Fix cciss SCSI rescan code to better notice device changes 2008-10-09 08:56:18 +02:00
cciss_scsi.h cciss: Fix cciss SCSI rescan code to better notice device changes 2008-10-09 08:56:18 +02:00
cpqarray.c cpqarray: enable bus mastering 2009-03-24 12:35:17 +01:00
cpqarray.h
cryptoloop.c drivers: Remove unnecessary inclusions of asm/semaphore.h 2008-04-18 22:16:32 -04:00
floppy.c platform: make better use of to_platform_{device,driver}() macros 2009-03-24 16:38:24 -07:00
hd.c hd: WIN_* -> ATA_CMD_* 2008-10-10 22:39:21 +02:00
ida_cmd.h
ida_ioctl.h
loop.c loop: add ioctl to resize a loop device 2009-04-01 08:59:17 -07:00
nbd.c nbd: fix I/O hang on disconnected nbds 2009-02-11 14:25:37 -08:00
pktcdvd.c pktcdvd: remove broken dev_t export of class devices 2008-12-10 10:03:32 -08:00
ps3disk.c powerpc/ps3: Printing fixups for l64 to ll64 conversion drivers/block 2009-01-16 16:15:13 +11:00
ps3vram.c proc 2/2: remove struct proc_dir_entry::owner 2009-03-31 01:14:44 +04:00
smart1,2.h
sunvdc.c sparc64: Fix unsigned long long warnings in drivers. 2009-01-06 13:20:38 -08:00
swim.c m68k: mac - Add SWIM floppy support 2009-03-26 21:15:27 +01:00
swim3.c [PATCH] switch swim3 2008-10-21 07:48:03 -04:00
swim_asm.S m68k: mac - Add SWIM floppy support 2009-03-26 21:15:27 +01:00
sx8.c block: replace remaining __FUNCTION__ occurrences 2008-04-21 09:51:04 +02:00
ub.c usb-storage: prepare for subdriver separation 2009-03-24 16:20:34 -07:00
umem.c Cleanup umem driver: fix most checkpatch warnings, conform to kernel 2007-12-18 08:29:28 +01:00
umem.h drivers/block/umem: trim trailing whitespace 2007-10-10 09:25:59 +02:00
viodasd.c [PATCH] switch viodasd 2008-10-21 07:48:07 -04:00
virtio_blk.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus 2008-12-30 17:37:25 -08:00
xd.c [PATCH] switch xd 2008-10-21 07:48:11 -04:00
xd.h [PATCH] switch xd 2008-10-21 07:48:11 -04:00
xen-blkfront.c Fix kernel NULL pointer dereference in xen-blkfront 2009-03-05 12:04:57 +01:00
xsysace.c Fix Xilinx SystemACE driver to handle empty CF slot 2009-03-14 21:06:52 +01:00
z2ram.c [PATCH] switch z2ram 2008-10-21 07:48:17 -04:00