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    Subject[PATCH 5.9 231/255] NFSv4.2: fix failure to unregister shrinker
    Date
    From: J. Bruce Fields <bfields@redhat.com>

    commit 70438afbf17e5194dd607dd17759560a363b7bb4 upstream.

    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>
    Fixes: 95ad37f90c33 "NFSv4.2: add client side xattr caching."
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>
    CC: stable@vger.kernel.org
    Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/nfs/nfs42xattr.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/fs/nfs/nfs42xattr.c
    +++ b/fs/nfs/nfs42xattr.c
    @@ -1048,8 +1048,10 @@ out4:

    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);

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