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Date:   Thu, 12 Nov 2020 09:03:40 -0500
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Trond Myklebust <trondmy@hammerspace.com>,
        Anna Schumaker <schumakeranna@gmail.com>
Cc:     linux-nfs@vger.kernel.org
Subject: Re: [PATCH] NFSv4.2: fix failure to unregister shrinker
Message-ID: <20201112140340.GB9243@fieldses.org>
References: <20201021143415.GA27122@fieldses.org>
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Looks like this patch got lost, do you need me to resend?

I should also have added a stable cc and a

	Fixes: 95ad37f90c33 "NFSv4.2: add client side xattr caching."

--b.

On Wed, Oct 21, 2020 at 10:34:15AM -0400, bfields wrote:
> From: "J. Bruce Fields" <bfields@redhat.com>
> 
> We forgot to unregister the nfs4_xattr_large_entry_shrinker.
> 
> That leaves the global list of shrinkers corrupted after unload of the
> nfs module, after which possibly unrelated code that calls
> register_shrinker() or unregister_shrinker() gets a BUG() with
> "supervisor write access in kernel mode".
> 
> And similarly for the nfs4_xattr_large_entry_lru.
> 
> Reported-by: Kris Karas <bugs-a17@moonlit-rail.com>
> Tested-By: Kris Karas <bugs-a17@moonlit-rail.com>
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> ---
>  fs/nfs/nfs42xattr.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/nfs/nfs42xattr.c b/fs/nfs/nfs42xattr.c
> index 86777996cfec..55b44a42d625 100644
> --- a/fs/nfs/nfs42xattr.c
> +++ b/fs/nfs/nfs42xattr.c
> @@ -1048,8 +1048,10 @@ int __init nfs4_xattr_cache_init(void)
>  
>  void nfs4_xattr_cache_exit(void)
>  {
> +	unregister_shrinker(&nfs4_xattr_large_entry_shrinker);
>  	unregister_shrinker(&nfs4_xattr_entry_shrinker);
>  	unregister_shrinker(&nfs4_xattr_cache_shrinker);
> +	list_lru_destroy(&nfs4_xattr_large_entry_lru);
>  	list_lru_destroy(&nfs4_xattr_entry_lru);
>  	list_lru_destroy(&nfs4_xattr_cache_lru);
>  	kmem_cache_destroy(nfs4_xattr_cache_cachep);
> -- 
> 2.26.2
>