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SubjectRe: [PATCH] Allow auto-destruction of loop devices.
On Sun, 28 Oct 2007 19:08:31 -0400
David Woodhouse <dwmw2@infradead.org> wrote:

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

Why do we want to do this?

>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 56e2304..7fae828 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -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;
> diff --git a/include/linux/loop.h b/include/linux/loop.h
> index 26a0a10..46169a7 100644
> --- a/include/linux/loop.h
> +++ b/include/linux/loop.h
> @@ -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 */
>
> --
> dwmw2
-
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