+ mm-gup-fix-memfd_pin_folios-hugetlb-page-allocation.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/gup: fix memfd_pin_folios hugetlb page allocation
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-gup-fix-memfd_pin_folios-hugetlb-page-allocation.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-fix-memfd_pin_folios-hugetlb-page-allocation.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Steve Sistare <steven.sistare@oracle.com>
Subject: mm/gup: fix memfd_pin_folios hugetlb page allocation
Date: Tue, 3 Sep 2024 07:25:20 -0700

When memfd_pin_folios -> memfd_alloc_folio creates a hugetlb page, the
index is wrong.  The subsequent call to filemap_get_folios_contig thus
cannot find it, and fails, and memfd_pin_folios loops forever.  To fix,
adjust the index for the huge_page_order.

memfd_alloc_folio also forgets to unlock the folio, so the next touch of
the page calls hugetlb_fault which blocks forever trying to take the lock.
Unlock it.

Link: https://lkml.kernel.org/r/1725373521-451395-5-git-send-email-steven.sistare@oracle.com
Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios")
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memfd.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/mm/memfd.c~mm-gup-fix-memfd_pin_folios-hugetlb-page-allocation
+++ a/mm/memfd.c
@@ -79,10 +79,13 @@ struct folio *memfd_alloc_folio(struct f
 		 * alloc from. Also, the folio will be pinned for an indefinite
 		 * amount of time, so it is not expected to be migrated away.
 		 */
-		gfp_mask = htlb_alloc_mask(hstate_file(memfd));
+		struct hstate *h = hstate_file(memfd);
+
+		gfp_mask = htlb_alloc_mask(h);
 		gfp_mask &= ~(__GFP_HIGHMEM | __GFP_MOVABLE);
+		idx >>= huge_page_order(h);
 
-		folio = alloc_hugetlb_folio_reserve(hstate_file(memfd),
+		folio = alloc_hugetlb_folio_reserve(h,
 						    numa_node_id(),
 						    NULL,
 						    gfp_mask);
@@ -95,6 +98,7 @@ struct folio *memfd_alloc_folio(struct f
 				free_huge_folio(folio);
 				return ERR_PTR(err);
 			}
+			folio_unlock(folio);
 			return folio;
 		}
 		return ERR_PTR(-ENOMEM);
_

Patches currently in -mm which might be from steven.sistare@oracle.com are

mm-filemap-fix-filemap_get_folios_contig-thp-panic.patch
mm-hugetlb-fix-memfd_pin_folios-free_huge_pages-leak.patch
mm-hugetlb-fix-memfd_pin_folios-resv_huge_pages-leak.patch
mm-gup-fix-memfd_pin_folios-hugetlb-page-allocation.patch
mm-gup-fix-memfd_pin_folios-alloc-race-panic.patch