[dm-devel] [PATCH] drop mutex in __set_size
Mikulas Patocka
mpatocka at redhat.com
Mon Jul 27 23:44:36 UTC 2009
On Thu, 23 Jul 2009, Jun'ichi Nomura wrote:
> Hi Alasdair, Mikulas,
>
> I found 2.6.31-rc includes the following commit:
> commit 32a926da5a16c01a8213331e5764472ce2f14a8d
> Author: Mikulas Patocka <mpatocka at redhat.com>
> Date: Mon Jun 22 10:12:17 2009 +0100
>
> which will introduce a deadlock problem described here:
> https://www.redhat.com/archives/dm-devel/2009-May/msg00097.html
> (or see below)
>
> Was the problem fixed/worked around somehow?
Hi.
I'd submit this. What do others think about it?
Mikulas
---
Drop the mutex.
It doesn't make sense to lock it for a single assignment, this code can't
be executed concurrently. The size should be read with i_size_read which
is automatically protected against concurrent i_size_write.
This locking can lead to a deadlock, if someone holds i_mutex while
the device is being suspended, described by Jun'ichi Nomura at
https://www.redhat.com/archives/dm-devel/2009-May/msg00097.html
Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
---
drivers/md/dm.c | 2 --
1 file changed, 2 deletions(-)
Index: linux-2.6.31-rc3-devel/drivers/md/dm.c
===================================================================
--- linux-2.6.31-rc3-devel.orig/drivers/md/dm.c 2009-07-28 01:20:17.000000000 +0200
+++ linux-2.6.31-rc3-devel/drivers/md/dm.c 2009-07-28 01:20:27.000000000 +0200
@@ -1901,9 +1901,7 @@ static void __set_size(struct mapped_dev
{
set_capacity(md->disk, size);
- mutex_lock(&md->bdev->bd_inode->i_mutex);
i_size_write(md->bdev->bd_inode, (loff_t)size << SECTOR_SHIFT);
- mutex_unlock(&md->bdev->bd_inode->i_mutex);
}
static int __bind(struct mapped_device *md, struct dm_table *t,
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