Re: [PATCH v4 2/3] mm/mempolicy: add set_mempolicy_home_node syscall

On 11/10/21 20:48, Jonathan Corbet wrote:

"Aneesh Kumar K.V" [off-list ref] writes:

quoted

This syscall can be used to set a home node for the MPOL_BIND
and MPOL_PREFERRED_MANY memory policy. Users should use this
syscall after setting up a memory policy for the specified range
as shown below.

So I noticed one little thing as I was looking at this...

[...]

quoted

+SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, len,
+		unsigned long, home_node, unsigned long, flags)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	struct mempolicy *new;
+	unsigned long vmstart;
+	unsigned long vmend;
+	unsigned long end;
+	int err = -ENOENT;
+
+	if (start & ~PAGE_MASK)
+		return -EINVAL;
+
+	len = (len + PAGE_SIZE - 1) & PAGE_MASK;
+	end = start + len;
+
+	if (end < start)
+		return -EINVAL;
+	if (end == start)
+		return 0;
+	mmap_write_lock(mm);
+	vma = find_vma(mm, start);
+	for (; vma && vma->vm_start < end;  vma = vma->vm_next) {
+
+		vmstart = max(start, vma->vm_start);
+		vmend   = min(end, vma->vm_end);
+		new = mpol_dup(vma_policy(vma));
+		if (IS_ERR(new)) {
+			err = PTR_ERR(new);
+			break;
+		}
+		/*
+		 * Only update home node if there is an existing vma policy
+		 */
+		if (!new)
+			continue;
+		new->home_node = home_node;
+		err = mbind_range(mm, vmstart, vmend, new);
+		if (err)
+			break;
+	}
+	mmap_write_unlock(mm);
+	return err;
+}

You never do anything with flags; I believe you want to check and ensure
that it's zero if there are no defined flags at this point?

Will update that in v5. I guess EINVAL is the right error for flags != 0?

-aneesh