[PATCH] Allow auto-destruction of loop devices.

[David Woodhouse <dwmw2@infradead.org>]

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

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

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