Commit fbf56346 authored Feb 03, 2020 by Steven Price Committed by Linus Torvalds Feb 04, 2020

mm: pagewalk: don't lock PTEs for walk_page_range_novma()

walk_page_range_novma() can be used to walk page tables or the kernel or
for firmware.  These page tables may contain entries that are not backed
by a struct page and so it isn't (in general) possible to take the PTE
lock for the pte_entry() callback.  So update walk_pte_range() to only
take the lock when no_vma==false by splitting out the inner loop to a
separate function and add a comment explaining the difference to
walk_page_range_novma().

Link: http://lkml.kernel.org/r/20191218162402.45610-14-steven.price@arm.com


Signed-off-by: Steven Price <steven.price@arm.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Liang, Kan" <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will@kernel.org>
Cc: Zong Li <zong.li@sifive.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 488ae6a2

mm/pagewalk.c

+28 −7

Original line number	Diff line number	Diff line
		@@ -4,15 +4,12 @@
		#include <linux/sched.h>
		#include <linux/hugetlb.h>

		static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
		struct mm_walk *walk)
		static int walk_pte_range_inner(pte_t *pte, unsigned long addr,
		unsigned long end, struct mm_walk *walk)
		{
		pte_t *pte;
		int err = 0;
		const struct mm_walk_ops *ops = walk->ops;
		spinlock_t *ptl;
		int err = 0;

		pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
		for (;;) {
		err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
		if (err)
		@@ -22,8 +19,26 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
		break;
		pte++;
		}
		return err;
		}

		static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
		struct mm_walk *walk)
		{
		pte_t *pte;
		int err = 0;
		spinlock_t *ptl;

		if (walk->no_vma) {
		pte = pte_offset_map(pmd, addr);
		err = walk_pte_range_inner(pte, addr, end, walk);
		pte_unmap(pte);
		} else {
		pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
		err = walk_pte_range_inner(pte, addr, end, walk);
		pte_unmap_unlock(pte, ptl);
		}

		return err;
		}

		@@ -394,6 +409,12 @@ int walk_page_range(struct mm_struct *mm, unsigned long start,
		return err;
		}

		/*
		* Similar to walk_page_range() but can walk any page tables even if they are
		* not backed by VMAs. Because 'unusual' entries may be walked this function
		* will also not lock the PTEs for the pte_entry() callback. This is useful for
		* walking the kernel pages tables or page tables for firmware.
		*/
		int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
		unsigned long end, const struct mm_walk_ops *ops,
		void *private)

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