kernfs: drop shared NUMA mempolicy hooks

It seems strange that kernfs should be an outlier with a set_policy and
get_policy in its kernfs_vm_ops.  Ah, it dates back to v2.6.30's commit
095160a ("sysfs: fix some bin_vm_ops errors"), when I had crashed on
powerpc's pci_mmap_legacy_page_range() fallback to shmem_zero_setup().

Well, that was commendably thorough, to give sysfs-bin a set_policy and
get_policy, just to avoid the way it was coded resulting in EINVAL from
mmap when CONFIG_NUMA; but somehow feels a bit over-the-top to me now.

It's easier to say that nobody should expect to manage a shmem object's
shared NUMA mempolicy via some kernfs backdoor to that object: delete that
code (and there's no longer an EINVAL from mmap in the NUMA case).

This then leaves set_policy/get_policy as implemented only by shmem -
though importantly also by SysV SHM, which has to interface with shmem
which implements them, and with SHM_HUGETLB which does not.

Link: https://lkml.kernel.org/r/302164-a760-4a9e-879b-6870c9b4013@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun heo <tj@kernel.org>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/kernfs/file.c

@@ -429,60 +429,11 @@ static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
 	return ret;
 }
 
-#ifdef CONFIG_NUMA
-static int kernfs_vma_set_policy(struct vm_area_struct *vma,
-				 struct mempolicy *new)
-{
-	struct file *file = vma->vm_file;
-	struct kernfs_open_file *of = kernfs_of(file);
-	int ret;
-
-	if (!of->vm_ops)
-		return 0;
-
-	if (!kernfs_get_active(of->kn))
-		return -EINVAL;
-
-	ret = 0;
-	if (of->vm_ops->set_policy)
-		ret = of->vm_ops->set_policy(vma, new);
-
-	kernfs_put_active(of->kn);
-	return ret;
-}
-
-static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
-					       unsigned long addr)
-{
-	struct file *file = vma->vm_file;
-	struct kernfs_open_file *of = kernfs_of(file);
-	struct mempolicy *pol;
-
-	if (!of->vm_ops)
-		return vma->vm_policy;
-
-	if (!kernfs_get_active(of->kn))
-		return vma->vm_policy;
-
-	pol = vma->vm_policy;
-	if (of->vm_ops->get_policy)
-		pol = of->vm_ops->get_policy(vma, addr);
-
-	kernfs_put_active(of->kn);
-	return pol;
-}
-
-#endif
-
 static const struct vm_operations_struct kernfs_vm_ops = {
 	.open		= kernfs_vma_open,
 	.fault		= kernfs_vma_fault,
 	.page_mkwrite	= kernfs_vma_page_mkwrite,
 	.access		= kernfs_vma_access,
-#ifdef CONFIG_NUMA
-	.set_policy	= kernfs_vma_set_policy,
-	.get_policy	= kernfs_vma_get_policy,
-#endif
 };
 
 static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)