Hi Matthew,

Thanks for reviewing this series.

On 12/01/2018 19:48, Matthew Wilcox wrote:

On Fri, Jan 12, 2018 at 06:26:00PM +0100, Laurent Dufour wrote:

quoted

-static void __vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
+static void __vma_rb_erase(struct vm_area_struct *vma, struct mm_struct *mm)
 {
+	struct rb_root *root = &mm->mm_rb;
 	/*
 	 * Note rb_erase_augmented is a fairly large inline function,
 	 * so make sure we instantiate it only once with our desired
 	 * augmented rbtree callbacks.
 	 */
+#ifdef CONFIG_SPF
+	write_lock(&mm->mm_rb_lock);
+#endif
 	rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
+#ifdef CONFIG_SPF
+	write_unlock(&mm->mm_rb_lock); /* wmb */
+#endif

I can't say I love this.  Have you considered:

#ifdef CONFIG_SPF
#define vma_rb_write_lock(mm)	write_lock(&mm->mm_rb_lock)
#define vma_rb_write_unlock(mm)	write_unlock(&mm->mm_rb_lock)
#else
#define vma_rb_write_lock(mm)	do { } while (0)
#define vma_rb_write_unlock(mm)	do { } while (0)
#endif

I haven't consider this, but this sounds to be smarter. I'll do that.

Also, SPF is kind of uninformative.  CONFIG_MM_SPF might be better?
Or perhaps even CONFIG_SPECULATIVE_PAGE_FAULT, just to make it really
painful to do these one-liner ifdefs that make the code so hard to read.

Thomas also complained about that, and I agree, SPF is quite cryptic. This
being said, I don't think that CONFIG_MM_SPF will be far better, so I'll
change this define to CONFIG_SPECULATIVE_PAGE_FAULT, even if it's longer,
it should not be too much present in the code.

Thanks,
Laurent.