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Re: xfs_iunlink_remove: xfs_inotobp() returned error 22 -- debugging

To: Brian Foster <bfoster@xxxxxxxxxx>
Subject: Re: xfs_iunlink_remove: xfs_inotobp() returned error 22 -- debugging
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Mon, 22 Apr 2013 14:59:54 -0500
Cc: yongtaofu@xxxxxxxxx, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <516C89DF.4070904@xxxxxxxxxx>
References: <516C89DF.4070904@xxxxxxxxxx>
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130328 Thunderbird/17.0.5
On 4/15/13 6:14 PM, Brian Foster wrote:
> Hi,
> 
> Thanks for the data in the previous thread:
> 
> http://oss.sgi.com/archives/xfs/2013-04/msg00327.html
> 
> I'm spinning off a new thread specifically for this because the original
> thread is already too large and scattered to track. As Eric stated,
> please try to keep data contained in as few messages as possible.
> 

Well, it's always simple in the end.  It just took a lot of debugging
to figure out what was happening - we do appreciate your help with that!

We were able to create a local reproducer, and it looks like
this patch fixes things:

commit aae8a97d3ec30788790d1720b71d76fd8eb44b73
Author: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Date:   Sat Jan 29 18:43:27 2011 +0530

    fs: Don't allow to create hardlink for deleted file
    
    Add inode->i_nlink == 0 check in VFS. Some of the file systems
    do this internally. A followup patch will remove those instance.
    This is needed to ensure that with link by handle we don't allow
    to create hardlink of an unlinked file. The check also prevent a race
    between unlink and link
    
    Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
    Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

diff --git a/fs/namei.c b/fs/namei.c
index 83e92ba..33be51a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2906,7 +2906,11 @@ int vfs_link(struct dentry *old_dentry, struct inode 
*dir, struct dentry *new_de
                return error;
 
        mutex_lock(&inode->i_mutex);
-       error = dir->i_op->link(old_dentry, dir, new_dentry);
+       /* Make sure we don't allow creating hardlink to an unlinked file */
+       if (inode->i_nlink == 0)
+               error =  -ENOENT;
+       else
+               error = dir->i_op->link(old_dentry, dir, new_dentry);
        mutex_unlock(&inode->i_mutex);
        if (!error)
                fsnotify_link(dir, inode, new_dentry);


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