[PATCH 1/1] fix d_revalidate oopsen on NFS exports

[Dave Kleikamp]

On 11/30/2011 06:47 PM, Chris Dunlop wrote:
> On Wed, Nov 30, 2011 at 08:54:43AM +0000, David Howells wrote:

...

>>
>> Acked-by: David Howells <dhowells at redhat.com>
>>
>> It's also worth printing a message - this *is* a kernel bug of some description
>> if it happens.
> 
> Like the below?  This covers the d_revalidate for 9p, afs, coda,
> hfs, ncpfs, proc, sysfs.
> 
> Note:  jfs isn't susceptible to this problem, but the resolution
> doesn't look like the other file systems, and from the comment
> I'm not sure if the problem was really understood and if it's
> doing the right thing:

This code, as well as the comments, were copied from vfat. It seems
reasonable for case-insensitive but case-preserving behavior (not jfs's
default). The safe thing is to drop the negative dentry if we don't know
the operation.

> 
> static int jfs_ci_revalidate(struct dentry *dentry, struct nameidata *nd)
> {
>         ...
>         /*
>          * This may be nfsd (or something), anyway, we can't see the
>          * intent of this. So, since this can be for creation, drop it.
>          */
>         if (!nd)
>                 return 0;
> 
>         /*
>          * Drop the negative dentry, in order to make sure to use the
>          * case sensitive name which is specified by user if this is
>          * for creation.
>          */
>         if (nd->flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
>                 return 0;
>         ...
> }
> 
> Chris.
>