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

From: Jun'ichi Nomura
Date: Thu Jan 28 2010 - 01:35:28 EST

>> On Sat, 16 Jan 2010 10:58:30 +0100
>> Fran__ois Figarola <francois.figarola@xxxxxxxxxxxx> 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 (
>>> The hardware is a Dell PowerEdge 2950 which runs fine with the
>>> 2.6.31.x kernel series (actually running with the latest,
>>> and the system is debian etch.
>>> Here is the trace of the bug I've got (using netconsole) with a
>>> 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@xxxxxx>
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?

Jun'ichi Nomura, NEC Corporation

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

Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>

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);
return sb;
@@ -307,7 +309,7 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
BUG_ON(sb->s_bdev != bdev);
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)

sb->s_frozen = SB_UNFROZEN;

if (sb)
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at