linux-kernel - [PATCH v2 16/19] mm: Remove follow

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Message-ID: <20240826204353.2228736-17-peterx@redhat.com>
Date: Mon, 26 Aug 2024 16:43:50 -0400
From: Peter Xu <peterx@...hat.com>
To: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Cc: Gavin Shan <gshan@...hat.com>,
	Catalin Marinas <catalin.marinas@....com>,
	x86@...nel.org,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alistair Popple <apopple@...dia.com>,
	kvm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Sean Christopherson <seanjc@...gle.com>,
	peterx@...hat.com,
	Oscar Salvador <osalvador@...e.de>,
	Jason Gunthorpe <jgg@...dia.com>,
	Borislav Petkov <bp@...en8.de>,
	Zi Yan <ziy@...dia.com>,
	Axel Rasmussen <axelrasmussen@...gle.com>,
	David Hildenbrand <david@...hat.com>,
	Yan Zhao <yan.y.zhao@...el.com>,
	Will Deacon <will@...nel.org>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	Alex Williamson <alex.williamson@...hat.com>
Subject: [PATCH v2 16/19] mm: Remove follow_pte()

follow_pte() users have been converted to follow_pfnmap*().  Remove the
API.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 include/linux/mm.h |  2 --
 mm/memory.c        | 73 ----------------------------------------------
 2 files changed, 75 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 161d496bfd18..b31d4bdd65ad 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2368,8 +2368,6 @@ void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
 		unsigned long end, unsigned long floor, unsigned long ceiling);
 int
 copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma);
-int follow_pte(struct vm_area_struct *vma, unsigned long address,
-	       pte_t **ptepp, spinlock_t **ptlp);
 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
 			void *buf, int len, int write);
 
diff --git a/mm/memory.c b/mm/memory.c
index b5d07f493d5d..288f81a8698e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6100,79 +6100,6 @@ int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
 }
 #endif /* __PAGETABLE_PMD_FOLDED */
 
-/**
- * follow_pte - look up PTE at a user virtual address
- * @vma: the memory mapping
- * @address: user virtual address
- * @ptepp: location to store found PTE
- * @ptlp: location to store the lock for the PTE
- *
- * On a successful return, the pointer to the PTE is stored in @ptepp;
- * the corresponding lock is taken and its location is stored in @ptlp.
- *
- * The contents of the PTE are only stable until @ptlp is released using
- * pte_unmap_unlock(). This function will fail if the PTE is non-present.
- * Present PTEs may include PTEs that map refcounted pages, such as
- * anonymous folios in COW mappings.
- *
- * Callers must be careful when relying on PTE content after
- * pte_unmap_unlock(). Especially if the PTE maps a refcounted page,
- * callers must protect against invalidation with MMU notifiers; otherwise
- * access to the PFN at a later point in time can trigger use-after-free.
- *
- * Only IO mappings and raw PFN mappings are allowed.  The mmap semaphore
- * should be taken for read.
- *
- * This function must not be used to modify PTE content.
- *
- * Return: zero on success, -ve otherwise.
- */
-int follow_pte(struct vm_area_struct *vma, unsigned long address,
-	       pte_t **ptepp, spinlock_t **ptlp)
-{
-	struct mm_struct *mm = vma->vm_mm;
-	pgd_t *pgd;
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *ptep;
-
-	mmap_assert_locked(mm);
-	if (unlikely(address < vma->vm_start || address >= vma->vm_end))
-		goto out;
-
-	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
-		goto out;
-
-	pgd = pgd_offset(mm, address);
-	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
-		goto out;
-
-	p4d = p4d_offset(pgd, address);
-	if (p4d_none(*p4d) || unlikely(p4d_bad(*p4d)))
-		goto out;
-
-	pud = pud_offset(p4d, address);
-	if (pud_none(*pud) || unlikely(pud_bad(*pud)))
-		goto out;
-
-	pmd = pmd_offset(pud, address);
-	VM_BUG_ON(pmd_trans_huge(*pmd));
-
-	ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
-	if (!ptep)
-		goto out;
-	if (!pte_present(ptep_get(ptep)))
-		goto unlock;
-	*ptepp = ptep;
-	return 0;
-unlock:
-	pte_unmap_unlock(ptep, *ptlp);
-out:
-	return -EINVAL;
-}
-EXPORT_SYMBOL_GPL(follow_pte);
-
 static inline void pfnmap_args_setup(struct follow_pfnmap_args *args,
 				     spinlock_t *lock, pte_t *ptep,
 				     pgprot_t pgprot, unsigned long pfn_base,
-- 
2.45.0