[PATCH] mm: Resolve some multi-size THP review nits

[Ryan Roberts <ryan.roberts@arm.com>]

Tidy code based on review feedback for final version of multi-size THP:

 - Comment added to explain alloc_anon_folio() error protocol
 - ifdefery simplified for alloc_anon_folio()

Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
---
Hi Andrew,

Hopefully this is the final tweak. Could you please squash this with the
"mm: thp: Support allocation of anonymous multi-size THP" patch in mm-unstable?

Or if you prefer me to re-post the entire series, just let me know.

Thanks,
Ryan


 mm/memory.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 8f0b936b90b5..3c530b639559 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4137,9 +4137,9 @@ static bool pte_range_none(pte_t *pte, int nr_pages)
 	return true;
 }

-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static struct folio *alloc_anon_folio(struct vm_fault *vmf)
 {
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	struct vm_area_struct *vma = vmf->vma;
 	unsigned long orders;
 	struct folio *folio;
@@ -4199,12 +4199,9 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf)
 	}

 fallback:
-	return vma_alloc_zeroed_movable_folio(vma, vmf->address);
-}
-#else
-#define alloc_anon_folio(vmf) \
-		vma_alloc_zeroed_movable_folio((vmf)->vma, (vmf)->address)
 #endif
+	return vma_alloc_zeroed_movable_folio(vmf->vma, vmf->address);
+}

 /*
  * We enter with non-exclusive mmap_lock (to exclude vma changes,
@@ -4260,6 +4257,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
 	/* Allocate our own private page. */
 	if (unlikely(anon_vma_prepare(vma)))
 		goto oom;
+	/* Returns NULL on OOM or ERR_PTR(-EAGAIN) if we must retry the fault */
 	folio = alloc_anon_folio(vmf);
 	if (IS_ERR(folio))
 		return 0;
--
2.25.1