[merged mm-stable] mm-hugetlb-consolidate-interpretation-of-gbl_chg-within-alloc_hugetlb_folio.patch removed from -mm tree

The quilt patch titled
     Subject: mm: hugetlb: consolidate interpretation of gbl_chg within alloc_hugetlb_folio()
has been removed from the -mm tree.  Its filename was
     mm-hugetlb-consolidate-interpretation-of-gbl_chg-within-alloc_hugetlb_folio.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Ackerley Tng <[email protected]>
Subject: mm: hugetlb: consolidate interpretation of gbl_chg within alloc_hugetlb_folio()
Date: Thu, 02 Jul 2026 09:21:45 -0700

Patch series "Open HugeTLB allocation routine for more generic use", v4.

The motivation for this patch series is guest_memfd, which would like to
use HugeTLB as a generic source of huge pages but not adopt HugeTLB's
reservation at mmap() time.

By refactoring alloc_hugetlb_folio() and some dependent functions, there
is now an option to allocate HugeTLB folios without providing a VMA. 
Specifically, HugeTLB allocation used to be dependent on the VMA to

1. Look up reservations in the resv_map
2. Get mpol, stored at vma->vm_policy

This refactoring provides hugetlb_alloc_folio(), which focuses on just the
allocation itself, and associated memory and HugeTLB charging (cgroups). 
alloc_hugetlb_folio() still handles reservations in the resv_map and
subpools.

Regarding naming, I'm definitely open to alternative names :) I chose
hugetlb_alloc_folio() because I'm seeing this function as a general
allocation function that is provided by the HugeTLB subsystem (hence the
hugetlb_ prefix).  I'm intending for alloc_hugetlb_folio() to be later
refactored as a static function for use just by HugeTLB, and HugeTLBfs
should probably use hugetlb_alloc_folio() directly.

To see how hugetlb_alloc_folio() is used by guest_memfd, the most recent
patch series that uses this more generic HugeTLB allocation routine is at
[1], and a newer revision of that patch series is at [2].

Independently of guest_memfd, I believe this change is useful in
simplifying alloc_hugetlb_folio().  alloc_hugetlb_folio() was so coupled
to a VMA that even HugeTLBfs allocates HugeTLB folios using a pseudo-VMA.


This patch (of 6):

The dequeue_hugetlb_folio_vma() function currently handles the gbl_chg
parameter to determine if a folio can be dequeued based on global page
availability.  This leaks reservation-specific logic into the dequeueing
path.

Relocate this logic to alloc_hugetlb_folio() so that
dequeue_hugetlb_folio_vma() focuses solely on selecting and dequeuing a
folio.  In alloc_hugetlb_folio(), only attempt to dequeue a folio if a
reservation exists (gbl_chg == 0) or if there are available huge pages in
the global pool.

No functional change intended.

Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/all/[email protected]/T/ [1]
Link: https://github.com/googleprodkernel/linux-cc/tree/wip-gmem-conversions-hugetlb-restructuring-12-08-25 [2]
Link: https://lore.kernel.org/all/[email protected]/ [3]
Link: https://sashiko.dev/#/patchset/[email protected] [4]
Signed-off-by: Ackerley Tng <[email protected]>
Reviewed-by: James Houghton <[email protected]>
Acked-by: Oscar Salvador <[email protected]>
Reviewed-by: Joshua Hahn <[email protected]>
Cc: Qi Zheng <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Byungchul Park <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: "Edgecombe, Rick P" <[email protected]>
Cc: Frank van der Linden <[email protected]>
Cc: Gregory Price <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Jiaqi Yan <[email protected]>
Cc: Matthew Brost <[email protected]>
Cc: Michael Roth <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Pasha Tatashin <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Pratyush Yadav <[email protected]>
Cc: Rakie Kim <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Shivank Garg <[email protected]>
Cc: Vishal Annapurve <[email protected]>
Cc: Yan Zhao <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/hugetlb.c |   27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

--- a/mm/hugetlb.c~mm-hugetlb-consolidate-interpretation-of-gbl_chg-within-alloc_hugetlb_folio
+++ a/mm/hugetlb.c
@@ -1318,7 +1318,7 @@ static unsigned long available_huge_page
 
 static struct folio *dequeue_hugetlb_folio_vma(struct hstate *h,
 				struct vm_area_struct *vma,
-				unsigned long address, long gbl_chg)
+				unsigned long address)
 {
 	struct folio *folio = NULL;
 	struct mempolicy *mpol;
@@ -1326,13 +1326,6 @@ static struct folio *dequeue_hugetlb_fol
 	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);
 
@@ -1350,9 +1343,6 @@ static struct folio *dequeue_hugetlb_fol
 
 	mpol_cond_put(mpol);
 	return folio;
-
-err:
-	return NULL;
 }
 
 #if defined(CONFIG_ARCH_HAS_GIGANTIC_PAGE) && defined(CONFIG_CONTIG_ALLOC)
@@ -2922,12 +2912,17 @@ struct folio *alloc_hugetlb_folio(struct
 		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.
-	 */
-	folio = dequeue_hugetlb_folio_vma(h, vma, addr, gbl_chg);
+	 * gbl_chg == 0 indicates a reservation exists for the
+	 * allocation, so try dequeuing a page. In case there was no
+	 * reservation, try dequeuing a page if there are available
+	 * pages in the global pool.
+	 */
+	folio = NULL;
+	if (!gbl_chg || available_huge_pages(h))
+		folio = dequeue_hugetlb_folio_vma(h, vma, addr);
+
 	if (!folio) {
 		spin_unlock_irq(&hugetlb_lock);
 		folio = alloc_buddy_hugetlb_folio_with_mpol(h, vma, addr);
_

Patches currently in -mm which might be from [email protected] are