[PATCH v3 03/12] mm/huge_memory: move THP gfp limit helper into header

[Kairui Song via B4 Relay <devnull+kasong.tencent.com@kernel.org>]

From: Kairui Song <kasong@tencent.com>

Shmem has some special requirements for THP GFP and has to limit it in
certain zones or provide a more lenient fallback.

We'll use this helper for generic swap THP allocation, which needs to
support shmem. For a typical GFP_HIGHUSER_MOVABLE swap-in, this helper
is basically a no-op. But it's necessary for certain shmem users, mostly
drivers.

No feature change.

Signed-off-by: Kairui Song <kasong@tencent.com>
---
 include/linux/huge_mm.h | 30 ++++++++++++++++++++++++++++++
 mm/shmem.c              | 30 +++---------------------------
 2 files changed, 33 insertions(+), 27 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 2949e5acff35..ffe5a120eee4 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -237,6 +237,31 @@ static inline bool thp_vma_suitable_order(struct vm_area_struct *vma,
 	return true;
 }
 
+/*
+ * Make sure huge_gfp is always more limited than limit_gfp.
+ * Some shmem users want THP allocation to be done less aggressively
+ * and only in certain zone.
+ */
+static inline gfp_t thp_limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
+{
+	gfp_t allowflags = __GFP_IO | __GFP_FS | __GFP_RECLAIM;
+	gfp_t denyflags = __GFP_NOWARN | __GFP_NORETRY;
+	gfp_t zoneflags = limit_gfp & GFP_ZONEMASK;
+	gfp_t result = huge_gfp & ~(allowflags | GFP_ZONEMASK);
+
+	/* Allow allocations only from the originally specified zones. */
+	result |= zoneflags;
+
+	/*
+	 * Minimize the result gfp by taking the union with the deny flags,
+	 * and the intersection of the allow flags.
+	 */
+	result |= (limit_gfp & denyflags);
+	result |= (huge_gfp & limit_gfp) & allowflags;
+
+	return result;
+}
+
 /*
  * Filter the bitfield of input orders to the ones suitable for use in the vma.
  * See thp_vma_suitable_order().
@@ -581,6 +606,11 @@ static inline bool thp_vma_suitable_order(struct vm_area_struct *vma,
 	return false;
 }
 
+static inline gfp_t thp_limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
+{
+	return huge_gfp;
+}
+
 static inline unsigned long thp_vma_suitable_orders(struct vm_area_struct *vma,
 		unsigned long addr, unsigned long orders)
 {
diff --git a/mm/shmem.c b/mm/shmem.c
index 3b5dc21b323c..5916acf594a8 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1791,30 +1791,6 @@ static struct folio *shmem_swapin_cluster(swp_entry_t swap, gfp_t gfp,
 	return folio;
 }
 
-/*
- * Make sure huge_gfp is always more limited than limit_gfp.
- * Some of the flags set permissions, while others set limitations.
- */
-static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
-{
-	gfp_t allowflags = __GFP_IO | __GFP_FS | __GFP_RECLAIM;
-	gfp_t denyflags = __GFP_NOWARN | __GFP_NORETRY;
-	gfp_t zoneflags = limit_gfp & GFP_ZONEMASK;
-	gfp_t result = huge_gfp & ~(allowflags | GFP_ZONEMASK);
-
-	/* Allow allocations only from the originally specified zones. */
-	result |= zoneflags;
-
-	/*
-	 * Minimize the result gfp by taking the union with the deny flags,
-	 * and the intersection of the allow flags.
-	 */
-	result |= (limit_gfp & denyflags);
-	result |= (huge_gfp & limit_gfp) & allowflags;
-
-	return result;
-}
-
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 bool shmem_hpage_pmd_enabled(void)
 {
@@ -2065,7 +2041,7 @@ static struct folio *shmem_swap_alloc_folio(struct inode *inode,
 		     non_swapcache_batch(entry, nr_pages) != nr_pages)
 			goto fallback;
 
-		alloc_gfp = limit_gfp_mask(vma_thp_gfp_mask(vma), gfp);
+		alloc_gfp = thp_limit_gfp_mask(vma_thp_gfp_mask(vma), gfp);
 	}
 retry:
 	new = shmem_alloc_folio(alloc_gfp, order, info, index);
@@ -2141,7 +2117,7 @@ static int shmem_replace_folio(struct folio **foliop, gfp_t gfp,
 	if (nr_pages > 1) {
 		gfp_t huge_gfp = vma_thp_gfp_mask(vma);
 
-		gfp = limit_gfp_mask(huge_gfp, gfp);
+		gfp = thp_limit_gfp_mask(huge_gfp, gfp);
 	}
 #endif
 
@@ -2548,7 +2524,7 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
 		gfp_t huge_gfp;
 
 		huge_gfp = vma_thp_gfp_mask(vma);
-		huge_gfp = limit_gfp_mask(huge_gfp, gfp);
+		huge_gfp = thp_limit_gfp_mask(huge_gfp, gfp);
 		folio = shmem_alloc_and_add_folio(vmf, huge_gfp,
 				inode, index, fault_mm, orders);
 		if (!IS_ERR(folio)) {

-- 
2.53.0