Commit 7780d040 authored by Hugh Dickins's avatar Hugh Dickins Committed by Andrew Morton
Browse files

mm/pagewalkers: ACTION_AGAIN if pte_offset_map_lock() fails 

Simple walk_page_range() users should set ACTION_AGAIN to retry when
pte_offset_map_lock() fails.

No need to check pmd_trans_unstable(): that was precisely to avoid the
possiblity of calling pte_offset_map() on a racily removed or inserted THP
entry, but such cases are now safely handled inside it.  Likewise there is
no need to check pmd_none() or pmd_bad() before calling it.

Link: https://lkml.kernel.org/r/c77d9d10-3aad-e3ce-4896-99e91c7947f3@google.com


Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Reviewed-by: SeongJae Park <sj@kernel.org> for mm/damon part
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Song Liu <song@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zack Rusin <zackr@vmware.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 2798bbe7

fs/proc/task_mmu.c

+16 −16
Original line number Diff line number Diff line
@@ -631,14 +631,11 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 
		goto out;

	}



	if (pmd_trans_unstable(pmd))

		goto out;

	/*

	 * The mmap_lock held all the way back in m_start() is what

	 * keeps khugepaged out of here and from collapsing things

	 * in here.

	 */

	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);

	if (!pte) {

		walk->action = ACTION_AGAIN;

		return 0;

	}

	for (; addr != end; pte++, addr += PAGE_SIZE)

		smaps_pte_entry(pte, addr, walk);

	pte_unmap_unlock(pte - 1, ptl);
@@ -1191,10 +1188,11 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr, 
		return 0;

	}



	if (pmd_trans_unstable(pmd))

		return 0;



	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);

	if (!pte) {

		walk->action = ACTION_AGAIN;

		return 0;

	}

	for (; addr != end; pte++, addr += PAGE_SIZE) {

		ptent = *pte;
@@ -1538,9 +1536,6 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, 
		spin_unlock(ptl);

		return err;

	}



	if (pmd_trans_unstable(pmdp))

		return 0;

#endif /* CONFIG_TRANSPARENT_HUGEPAGE */



	/*
@@ -1548,6 +1543,10 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, 
	 * goes beyond vma->vm_end.

	 */

	orig_pte = pte = pte_offset_map_lock(walk->mm, pmdp, addr, &ptl);

	if (!pte) {

		walk->action = ACTION_AGAIN;

		return err;

	}

	for (; addr < end; pte++, addr += PAGE_SIZE) {

		pagemap_entry_t pme;
@@ -1887,11 +1886,12 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr, 
		spin_unlock(ptl);

		return 0;

	}



	if (pmd_trans_unstable(pmd))

		return 0;

#endif

	orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);

	if (!pte) {

		walk->action = ACTION_AGAIN;

		return 0;

	}

	do {

		struct page *page = can_gather_numa_stats(*pte, vma, addr);

		if (!page)

mm/damon/vaddr.c

+8 −4
Original line number Diff line number Diff line
@@ -318,9 +318,11 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr, 
		spin_unlock(ptl);

	}



	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))

		return 0;

	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);

	if (!pte) {

		walk->action = ACTION_AGAIN;

		return 0;

	}

	if (!pte_present(*pte))

		goto out;

	damon_ptep_mkold(pte, walk->vma, addr);
@@ -464,9 +466,11 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr, 
regular_page:

#endif	/* CONFIG_TRANSPARENT_HUGEPAGE */



	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))

		return -EINVAL;

	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);

	if (!pte) {

		walk->action = ACTION_AGAIN;

		return 0;

	}

	if (!pte_present(*pte))

		goto out;

	folio = damon_get_folio(pte_pfn(*pte));

mm/mempolicy.c

+4 −3
Original line number Diff line number Diff line
@@ -514,10 +514,11 @@ static int queue_folios_pte_range(pmd_t *pmd, unsigned long addr, 
	if (ptl)

		return queue_folios_pmd(pmd, ptl, addr, end, walk);



	if (pmd_trans_unstable(pmd))

		return 0;



	mapped_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);

	if (!pte) {

		walk->action = ACTION_AGAIN;

		return 0;

	}

	for (; addr != end; pte++, addr += PAGE_SIZE) {

		if (!pte_present(*pte))

			continue;

mm/mincore.c

+4 −5
Original line number Diff line number Diff line
@@ -113,12 +113,11 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 
		goto out;

	}



	if (pmd_trans_unstable(pmd)) {

		__mincore_unmapped_range(addr, end, vma, vec);

		goto out;

	}



	ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);

	if (!ptep) {

		walk->action = ACTION_AGAIN;

		return 0;

	}

	for (; addr != end; ptep++, addr += PAGE_SIZE) {

		pte_t pte = *ptep;

mm/mlock.c

+4 −0
Original line number Diff line number Diff line
@@ -329,6 +329,10 @@ static int mlock_pte_range(pmd_t *pmd, unsigned long addr, 
	}



	start_pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);

	if (!start_pte) {

		walk->action = ACTION_AGAIN;

		return 0;

	}

	for (pte = start_pte; addr != end; pte++, addr += PAGE_SIZE) {

		if (!pte_present(*pte))

			continue;