Commit 7f760917 authored by David Hildenbrand's avatar David Hildenbrand Committed by Linus Torvalds
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mm/huge_memory: remove stale locking logic from __split_huge_pmd() 

Let's remove the stale logic that was required for reuse_swap_page().

[akpm@linux-foundation.org: simplification, per Yang Shi]

Link: https://lkml.kernel.org/r/20220131162940.210846-10-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liang Zhang <zhangliang5@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 55c62fa7

mm/huge_memory.c

+4 −36
Original line number Diff line number Diff line
@@ -2133,8 +2133,6 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 
{

	spinlock_t *ptl;

	struct mmu_notifier_range range;

	bool do_unlock_folio = false;

	pmd_t _pmd;



	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,

				address & HPAGE_PMD_MASK,
@@ -2153,42 +2151,12 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, 
			goto out;

	}



repeat:

	if (pmd_trans_huge(*pmd)) {

		if (!folio) {

			folio = page_folio(pmd_page(*pmd));

			/*

			 * An anonymous page must be locked, to ensure that a

			 * concurrent reuse_swap_page() sees stable mapcount;

			 * but reuse_swap_page() is not used on shmem or file,

			 * and page lock must not be taken when zap_pmd_range()

			 * calls __split_huge_pmd() while i_mmap_lock is held.

			 */

			if (folio_test_anon(folio)) {

				if (unlikely(!folio_trylock(folio))) {

					folio_get(folio);

					_pmd = *pmd;

					spin_unlock(ptl);

					folio_lock(folio);

					spin_lock(ptl);

					if (unlikely(!pmd_same(*pmd, _pmd))) {

						folio_unlock(folio);

						folio_put(folio);

						folio = NULL;

						goto repeat;

					}

					folio_put(folio);

				}

				do_unlock_folio = true;

			}

		}

	} else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))

		goto out;

	if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||

	    is_pmd_migration_entry(*pmd))

		__split_huge_pmd_locked(vma, pmd, range.start, freeze);



out:

	spin_unlock(ptl);

	if (do_unlock_folio)

		folio_unlock(folio);

	/*

	 * No need to double call mmu_notifier->invalidate_range() callback.

	 * They are 3 cases to consider inside __split_huge_pmd_locked():