FAILED: patch "[PATCH] mm/hugetlb: fix missing hugetlb_lock for resv uncharge" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x b76b46902c2d0395488c8412e1116c2486cdfcb2
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024042949-discolor-mop-d6e8@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

b76b46902c2d ("mm/hugetlb: fix missing hugetlb_lock for resv uncharge") d4ab0316cc33 ("mm/hugetlb_cgroup: convert hugetlb_cgroup_uncharge_page() to folios") 0356c4b96f68 ("mm/hugetlb: convert free_huge_page to folios")
78fbe906cc90 ("mm/page-flags: reuse PG_mappedtodisk as PG_anon_exclusive for PageAnon() pages") c145e0b47c77 ("mm: streamline COW logic in do_swap_page()")
84d60fdd3733 ("mm: slightly clarify KSM logic in do_swap_page()")
5cbf9942c963 ("mm: generalize the pgmap based page_free infrastructure") 27674ef6c73f ("mm: remove the extra ZONE_DEVICE struct page refcount") dc90f0846df4 ("mm: don't include <linux/memremap.h> in <linux/mm.h>") 895749455f60 ("mm: simplify freeing of devmap managed pages")
75e55d8a107e ("mm: move free_devmap_managed_page to memremap.c")
730ff52194cd ("mm: remove pointless includes from <linux/hmm.h>")
f56caedaf94f ("Merge branch 'akpm' (patches from Andrew)")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b76b46902c2d0395488c8412e1116c2486cdfcb2 Mon Sep 17 00:00:00 2001
From: Peter Xu <[email protected]>
Date: Wed, 17 Apr 2024 17:18:35 -0400
Subject: [PATCH] mm/hugetlb: fix missing hugetlb_lock for resv uncharge

There is a recent report on UFFDIO_COPY over hugetlb:

https://lore.kernel.org/all/[email protected]/

350: lockdep_assert_held(&hugetlb_lock);

Should be an issue in hugetlb but triggered in an userfault context, where it goes into the unlikely path where two threads modifying the resv map together. Mike has a fix in that path for resv uncharge but it looks like the locking criteria was overlooked: hugetlb_cgroup_uncharge_folio_rsvd() will update the cgroup pointer, so it requires to be called with the lock held.

index 31d00eee028f..53e0ab5c0845 100644
@@ -3268,9 +3268,12 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
 
 		rsv_adjust = hugepage_subpool_put_pages(spool, 1);
 		hugetlb_acct_memory(h, -rsv_adjust);
-		if (deferred_reserve)
+		if (deferred_reserve) {
+			spin_lock_irq(&hugetlb_lock);
 			hugetlb_cgroup_uncharge_folio_rsvd(hstate_index(h),
 					pages_per_huge_page(h), folio);
+			spin_unlock_irq(&hugetlb_lock);
+		}
 	}
 
 	if (!memcg_charge_ret)