linux-kernel - [RFC PATCH v2 16/51] mm: hugetlb: Consolidate interpretation of gbl_chg within alloc_hugetlb

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Message-ID: <8548af334e01401a776aae37a0e9f30f9ffbba8c.1747264138.git.ackerleytng@google.com>
Date: Wed, 14 May 2025 16:41:55 -0700
From: Ackerley Tng <ackerleytng@...gle.com>
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Subject: [RFC PATCH v2 16/51] mm: hugetlb: Consolidate interpretation of
 gbl_chg within alloc_hugetlb_folio()

Previously, gbl_chg was passed from alloc_hugetlb_folio() into
dequeue_hugetlb_folio_vma(), leaking the concept of gbl_chg into
dequeue_hugetlb_folio_vma().

This patch consolidates the interpretation of gbl_chg into
alloc_hugetlb_folio(), also renaming dequeue_hugetlb_folio_vma() to
dequeue_hugetlb_folio() so dequeue_hugetlb_folio() can just focus on
dequeuing a folio.

Change-Id: I31bf48af2400b6e13b44d03c8be22ce1a9092a9c
Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
---
 mm/hugetlb.c | 28 +++++++++++-----------------
 1 file changed, 11 insertions(+), 17 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6ea1be71aa42..b843e869496f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1364,9 +1364,9 @@ static unsigned long available_huge_pages(struct hstate *h)
 	return h->free_huge_pages - h->resv_huge_pages;
 }
 
-static struct folio *dequeue_hugetlb_folio_vma(struct hstate *h,
-				struct vm_area_struct *vma,
-				unsigned long address, long gbl_chg)
+static struct folio *dequeue_hugetlb_folio(struct hstate *h,
+					   struct vm_area_struct *vma,
+					   unsigned long address)
 {
 	struct folio *folio = NULL;
 	struct mempolicy *mpol;
@@ -1374,13 +1374,6 @@ static struct folio *dequeue_hugetlb_folio_vma(struct hstate *h,
 	nodemask_t *nodemask;
 	int nid;
 
-	/*
-	 * gbl_chg==1 means the allocation requires a new page that was not
-	 * reserved before.  Making sure there's at least one free page.
-	 */
-	if (gbl_chg && !available_huge_pages(h))
-		goto err;
-
 	gfp_mask = htlb_alloc_mask(h);
 	nid = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
 
@@ -1398,9 +1391,6 @@ static struct folio *dequeue_hugetlb_folio_vma(struct hstate *h,
 
 	mpol_cond_put(mpol);
 	return folio;
-
-err:
-	return NULL;
 }
 
 /*
@@ -3074,12 +3064,16 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
 		goto out_uncharge_cgroup_reservation;
 
 	spin_lock_irq(&hugetlb_lock);
+
 	/*
-	 * glb_chg is passed to indicate whether or not a page must be taken
-	 * from the global free pool (global change).  gbl_chg == 0 indicates
-	 * a reservation exists for the allocation.
+	 * gbl_chg == 0 indicates a reservation exists for the allocation - so
+	 * try dequeuing a page. If there are available_huge_pages(), try using
+	 * them!
 	 */
-	folio = dequeue_hugetlb_folio_vma(h, vma, addr, gbl_chg);
+	folio = NULL;
+	if (!gbl_chg || available_huge_pages(h))
+		folio = dequeue_hugetlb_folio(h, vma, addr);
+
 	if (!folio) {
 		spin_unlock_irq(&hugetlb_lock);
 		folio = alloc_buddy_hugetlb_folio_with_mpol(h, vma, addr);
-- 
2.49.0.1045.g170613ef41-goog