Patchwork Ext2: do not mark_inode_dirty to avoid BUG_ON

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Submitter fanchaoting
Date March 12, 2013, 5:06 a.m.
Message ID <513EB7DD.3020103@cn.fujitsu.com>
Download mbox | patch
Permalink /patch/226778/
State Not Applicable
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fanchaoting - March 12, 2013, 5:06 a.m.
From: Wang Shilong <wangsl-fnst@cn.fujitsu.com>

commit 8e3dffc651cb668e1ff4d8b89cc1c3dde7540d3b leads into
a regression that casue BUG_ON when unlinking inode.

Reported-by: tyhicks@canonical.com
Signed-off-by: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
---
 fs/ext2/balloc.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

-- 1.7.7.6 




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Lukas Czerner - March 12, 2013, 8:14 a.m.
On Tue, 12 Mar 2013, fanchaoting wrote:

> Date: Tue, 12 Mar 2013 13:06:37 +0800
> From: fanchaoting <fanchaoting@cn.fujitsu.com>
> To: jack@suse.cz
> Cc: tyhicks@canonical.com, linux-ext4@vger.kernel.org,
>     wangshilong1991@gmail.com
> Subject: [PATCH] Ext2: do not mark_inode_dirty to avoid BUG_ON
> 
> From: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
> 
> commit 8e3dffc651cb668e1ff4d8b89cc1c3dde7540d3b leads into
> a regression that casue BUG_ON when unlinking inode.

Hi,

it seems to be that we do need to mark the inode dirty, because
we're changing inode->i_blocks from within
dquot_free_block_nodirty().

However looking at the code we usually call mark_inode_dirty(inode)
after we call ext2_free_blocks() except when we're about to remove
the inode so it seems that having that call within ext2_free_blocks()
is not necessary.

However I am not sure about the error path in ext2_alloc_branch()
which does not dirty the inode after calling ext2_free_blocks().
However presumably since we're just undoing the changes we might
have done and not actually allocating, or freeing any space for
real, dirtying the inode might not be necessary. Can you confirm
that ?

Thanks!
-Lukas

> 
> Reported-by: tyhicks@canonical.com
> Signed-off-by: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
> ---
>  fs/ext2/balloc.c |    1 -
>  1 files changed, 0 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
> index 9f9992b..06d82fc 100644
> --- a/fs/ext2/balloc.c
> +++ b/fs/ext2/balloc.c
> @@ -562,7 +562,6 @@ error_return:
>  	if (freed) {
>  		percpu_counter_add(&sbi->s_freeblocks_counter, freed);
>  		dquot_free_block_nodirty(inode, freed);
> -		mark_inode_dirty(inode);
>  	}
>  }
>  
> -- 1.7.7.6 
> 
> 
> 
> 
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Jan Kara - March 12, 2013, 10:13 a.m.
On Tue 12-03-13 09:14:21, Lukáš Czerner wrote:
> On Tue, 12 Mar 2013, fanchaoting wrote:
> 
> > Date: Tue, 12 Mar 2013 13:06:37 +0800
> > From: fanchaoting <fanchaoting@cn.fujitsu.com>
> > To: jack@suse.cz
> > Cc: tyhicks@canonical.com, linux-ext4@vger.kernel.org,
> >     wangshilong1991@gmail.com
> > Subject: [PATCH] Ext2: do not mark_inode_dirty to avoid BUG_ON
> > 
> > From: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
> > 
> > commit 8e3dffc651cb668e1ff4d8b89cc1c3dde7540d3b leads into
> > a regression that casue BUG_ON when unlinking inode.
> 
> Hi,
> 
> it seems to be that we do need to mark the inode dirty, because
> we're changing inode->i_blocks from within
> dquot_free_block_nodirty().
> 
> However looking at the code we usually call mark_inode_dirty(inode)
> after we call ext2_free_blocks() except when we're about to remove
> the inode so it seems that having that call within ext2_free_blocks()
> is not necessary.
  Yeah. Actually the problem is specifically with ext2_xattr_delete_inode()
marking inode dirty because that is called after clear_inode(). Everything
before clear_inode() call is free to dirty the inode because clear_inode()
clears the dirty flag. I wonder if we shouldn't move that call into
ext2_evict_inode() before clear_inode() and be done with it. Because the
fact that ext2_free_blocks() cannot dirty the inode looks more surprising
than the fact that ext2_free_inode() doesn't automatically free extended
attributes.

> However I am not sure about the error path in ext2_alloc_branch()
> which does not dirty the inode after calling ext2_free_blocks().
> However presumably since we're just undoing the changes we might
> have done and not actually allocating, or freeing any space for
> real, dirtying the inode might not be necessary. Can you confirm
> that ?
  I think that needs to dirty the inode. It may be written out in some
intermediate state...

								Honza

> > Reported-by: tyhicks@canonical.com
> > Signed-off-by: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
> > ---
> >  fs/ext2/balloc.c |    1 -
> >  1 files changed, 0 insertions(+), 1 deletions(-)
> > 
> > diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
> > index 9f9992b..06d82fc 100644
> > --- a/fs/ext2/balloc.c
> > +++ b/fs/ext2/balloc.c
> > @@ -562,7 +562,6 @@ error_return:
> >  	if (freed) {
> >  		percpu_counter_add(&sbi->s_freeblocks_counter, freed);
> >  		dquot_free_block_nodirty(inode, freed);
> > -		mark_inode_dirty(inode);
> >  	}
> >  }
> >  
> > -- 1.7.7.6 
> > 
> > 
> > 
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >

Patch

diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
index 9f9992b..06d82fc 100644
--- a/fs/ext2/balloc.c
+++ b/fs/ext2/balloc.c
@@ -562,7 +562,6 @@  error_return:
 	if (freed) {
 		percpu_counter_add(&sbi->s_freeblocks_counter, freed);
 		dquot_free_block_nodirty(inode, freed);
-		mark_inode_dirty(inode);
 	}
 }