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SubjectRe: online resizing of devices/filesystems (2.6)
Date
On Friday 17 October 2003 15:49, Kevin Corry wrote:
> On Friday 17 October 2003 15:05, Andrew Morton wrote:
> > So one approach would be to do what NBD does, and just write i_size
> > directly.
>
> We had considered that originally. It just seemed like too big of a hack.
> :) Plus I wasn't sure if there were locking issues with changing fields in
> the inode.
>
> > You could create a little helper library function which takes i_sem and
> > then writes i_size. But the VFS tends to avoid taking i_sem on blockdevs
> > because it doesn't expect i_size to change ;)
>
> So...should I take i_sem or not? :) Perhaps calling i_size_write() in
> include/linux/fs.h would be preferrable, since it seems to be doing
> different things for SMP and preempt.
>
> Thanks for the feedback!

Here's a patch that takes bdev->bd_inode->i_sem, and then calls
i_size_write() to update the inode size. My initial tests have been
successful in resizing mounted reiser and xfs filesystems on
2.6.0-test7.

--
Kevin Corry
kevcorry@us.ibm.com
http://evms.sourceforge.net/


When setting the size of a Device-Mapper device in the gendisk entry, also try
to set the size of the corresponding block_device entry's inode. This is
necessary to allow online device/filesystem resizing to work correctly.

--- a/drivers/md/dm.c 9 Oct 2003 16:47:44 -0000
+++ b/drivers/md/dm.c 17 Oct 2003 21:06:01 -0000
@@ -726,6 +726,20 @@
up_write(&md->lock);
}

+static void __set_size(struct gendisk *disk, sector_t size)
+{
+ struct block_device *bdev;
+
+ set_capacity(disk, size);
+ bdev = bdget_disk(disk, 0);
+ if (bdev) {
+ down(&bdev->bd_inode->i_sem);
+ i_size_write(bdev->bd_inode, size << SECTOR_SHIFT);
+ up(&bdev->bd_inode->i_sem);
+ bdput(bdev);
+ }
+}
+
static int __bind(struct mapped_device *md, struct dm_table *t)
{
request_queue_t *q = md->queue;
@@ -733,7 +747,7 @@
md->map = t;

size = dm_table_get_size(t);
- set_capacity(md->disk, size);
+ __set_size(md->disk, size);
if (size == 0)
return 0;

-
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