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Subject[PATCH v2] loop file resizable
Date

Revise the patch to be available to the latest linux-2.6.git tree.

----------------------------------------------------------------------
Add the ability to 'resize' the loop device on the fly.
This may be practically very useful.
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.

Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
Signed-off-by: Tomas Matejicek <tomas@slax.org>
---
drivers/block/loop.c | 26 ++++++++++++++++++++++++++
include/linux/loop.h | 1 +
2 files changed, 27 insertions(+), 0 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 5c4ee70..a034bf9 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1137,6 +1137,28 @@ loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
return err;
}

+static int loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
+{
+ int err;
+ sector_t sec;
+ loff_t sz;
+
+ err = -ENXIO;
+ if (unlikely(lo->lo_state != Lo_bound))
+ goto out;
+ err = figure_loop_size(lo);
+ if (unlikely(err))
+ goto out;
+ sec = get_capacity(lo->lo_disk);
+ sz = sec << 9;
+ mutex_lock(&bdev->bd_mutex);
+ bd_set_size(bdev, sz);
+ mutex_unlock(&bdev->bd_mutex);
+
+ out:
+ return err;
+}
+
static int lo_ioctl(struct block_device *bdev, fmode_t mode,
unsigned int cmd, unsigned long arg)
{
@@ -1166,6 +1188,9 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
case LOOP_GET_STATUS64:
err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
break;
+ case LOOP_SET_CAPACITY:
+ err = loop_set_capacity(lo, bdev);
+ break;
default:
err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
}
@@ -1311,6 +1336,7 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
lo, (struct compat_loop_info __user *) arg);
mutex_unlock(&lo->lo_ctl_mutex);
break;
+ case LOOP_SET_CAPACITY:
case LOOP_CLR_FD:
case LOOP_GET_STATUS64:
case LOOP_SET_STATUS64:
diff --git a/include/linux/loop.h b/include/linux/loop.h
index 46169a7..e9e002a 100644
--- a/include/linux/loop.h
+++ b/include/linux/loop.h
@@ -160,5 +160,6 @@ int loop_unregister_transfer(int number);
#define LOOP_SET_STATUS64 0x4C04
#define LOOP_GET_STATUS64 0x4C05
#define LOOP_CHANGE_FD 0x4C06
+#define LOOP_SET_CAPACITY 0x4C07

#endif
--

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