Commit 96c58655 authored Feb 06, 2008 by David Woodhouse Committed by Linus Torvalds Feb 06, 2008

Allow auto-destruction of loop devices

This allows a flag to be set on loop devices so that when they are
closed for the last time, they'll self-destruct.

In general, so that we can automatically allocate loop devices (as with
losetup -f) and have them disappear when we're done with them.

In particular, right now, so that we can stop relying on the hackish
special-case in umount(8) which kills off loop devices which were set up by
'mount -oloop'.  That means we can stop putting crap in /etc/mtab which
doesn't belong there, which means it can be a symlink to /proc/mounts, which
means yet another writable file on the root filesystem is eliminated and the
'stateless' folks get happier...  and OLPC trac #356 can be closed.

The mount(8) side of that is at
http://marc.info/?l=util-linux-ng&m=119362955431694&w=2



[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Cc: Bernardo Innocenti <bernie@codewiz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a3b81113

drivers/block/loop.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -973,6 +973,10 @@ loop_set_status(struct loop_device lo, const struct loop_info64 info)
		lo->transfer = xfer->transfer;
		lo->ioctl = xfer->ioctl;

		if ((lo->lo_flags & LO_FLAGS_AUTOCLEAR) !=
		(info->lo_flags & LO_FLAGS_AUTOCLEAR))
		lo->lo_flags ^= LO_FLAGS_AUTOCLEAR;

		lo->lo_encrypt_key_size = info->lo_encrypt_key_size;
		lo->lo_init[0] = info->lo_init[0];
		lo->lo_init[1] = info->lo_init[1];
		@@ -1331,6 +1335,10 @@ static int lo_release(struct inode inode, struct file file)

		mutex_lock(&lo->lo_ctl_mutex);
		--lo->lo_refcnt;

		if ((lo->lo_flags & LO_FLAGS_AUTOCLEAR) && !lo->lo_refcnt)
		loop_clr_fd(lo, inode->i_bdev);

		mutex_unlock(&lo->lo_ctl_mutex);

		return 0;

include/linux/loop.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -76,6 +76,7 @@ struct loop_device {
		enum {
		LO_FLAGS_READ_ONLY = 1,
		LO_FLAGS_USE_AOPS = 2,
		LO_FLAGS_AUTOCLEAR = 4,
		};

		#include <asm/posix_types.h> /* for __kernel_old_dev_t */

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