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Re: [dm-devel] [BUG] kernel 2.6.32.x hangs during boot process



28.01.2010 08:32, Jun'ichi Nomura skrev:
On Sat, 16 Jan 2010 10:58:30 +0100
Fran__ois Figarola<francois figarola i-consult fr>  wrote:
Since I've tried to boot 2.6.32.x kernel, my system hangs during the
boot process, and I think it could be related to the problem reported
earlier by Megastorage (http://lkml.org/lkml/2010/1/10/92).

The hardware is a Dell PowerEdge 2950 which runs fine with the
2.6.31.x kernel series (actually running with the latest 2.6.31.11),
and the system is debian etch.

Here is the trace of the bug I've got (using netconsole) with a
2.6.32.3 kernel :

BUG: Dentry ffff880667690000{i=41a46,n=sleep} still in use (8)
[unmount of ext3 dm-4]
------------[ cut here ]------------
kernel BUG at fs/dcache.c:670!

I can reproduce this when suspend/resume read-only mounted dm device.

When MS_RDONLY, both freeze_bdev and thaw_bdev call deactivate_locked_super,
which seems wrong. The change was introduced with the commit below:

   commit 4504230a71566785a05d3e6b53fa1ee071b864eb
   Author: Christoph Hellwig<hch lst de>
   Date:   Mon Aug 3 23:28:35 2009 +0200

   freeze_bdev: grab active reference to frozen superblocks

With the attached patch, both remount-ro and remount-rw are
rejected as EBUSY on freezed device as expected.

Christoph, do you think this is the right fix?


I can confirm that both reverting the above patch, or applying the fix below fixes the issue on both 2.6.32 and 2.6.33-rc5

So if it's considered the correct fix, it needs to be cc stable@ for 2.6.32

(I reported this same issue this morning here:
 http://marc.info/?l=linux-kernel&m=126467195500908&w=2,
 but then I found this thread/fix)

The system I have tested on is a 4-disk dmraid10 connected to an Intel ICH10R on an Asus P7P55D Deluxe running x86_64

Jun'ichi Nomura, NEC Corporation


If MS_RDONLY, freeze_bdev should just up_write(s_umount) instead of
deactivate_locked_super().
Also, keep sb->s_frozen consistent so that remount can check the frozen state.

Signed-off-by: Jun'ichi Nomura <j-nomura ce jp nec com>
  Tested-by: Thomas Backlund <tmb mandriva org>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 73d6a73..600261f 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -246,7 +246,9 @@ struct super_block *freeze_bdev(struct block_device *bdev)
 	if (!sb)
 		goto out;
 	if (sb->s_flags & MS_RDONLY) {
-		deactivate_locked_super(sb);
+		sb->s_frozen = SB_FREEZE_TRANS;
+		smp_wmb();
+		up_write(&sb->s_umount);
 		mutex_unlock(&bdev->bd_fsfreeze_mutex);
 		return sb;
 	}
@@ -307,7 +309,7 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
 	BUG_ON(sb->s_bdev != bdev);
 	down_write(&sb->s_umount);
 	if (sb->s_flags & MS_RDONLY)
-		goto out_deactivate;
+		goto out_unfrozen;

 	if (sb->s_op->unfreeze_fs) {
 		error = sb->s_op->unfreeze_fs(sb);
@@ -321,11 +323,11 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
 		}
 	}

+out_unfrozen:
 	sb->s_frozen = SB_UNFROZEN;
 	smp_wmb();
 	wake_up(&sb->s_wait_unfrozen);

-out_deactivate:
 	if (sb)
 		deactivate_locked_super(sb);
 out_unlock:


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