Commit 5c7f3bf0 authored by Hugh Dickins's avatar Hugh Dickins Committed by Andrew Morton
Browse files

s390: allow pte_offset_map_lock() to fail 

In rare transient cases, not yet made possible, pte_offset_map() and
pte_offset_map_lock() may not find a page table: handle appropriately.

Add comment on mm's contract with s390 above __zap_zero_pages(),
and fix old comment there: must be called after THP was disabled.

Link: https://lkml.kernel.org/r/3ff29363-336a-9733-12a1-5c31a45c8aeb@google.com


Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: John David Anglin <dave.anglin@bell.net>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 893f667f

arch/s390/kernel/uv.c

+2 −0
Original line number Diff line number Diff line
@@ -294,6 +294,8 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb) 


	rc = -ENXIO;

	ptep = get_locked_pte(gmap->mm, uaddr, &ptelock);

	if (!ptep)

		goto out;

	if (pte_present(*ptep) && !(pte_val(*ptep) & _PAGE_INVALID) && pte_write(*ptep)) {

		page = pte_page(*ptep);

		rc = -EAGAIN;

arch/s390/mm/gmap.c

+8 −1
Original line number Diff line number Diff line
@@ -2537,7 +2537,12 @@ static inline void thp_split_mm(struct mm_struct *mm) 
 * Remove all empty zero pages from the mapping for lazy refaulting

 * - This must be called after mm->context.has_pgste is set, to avoid

 *   future creation of zero pages

 * - This must be called after THP was enabled

 * - This must be called after THP was disabled.

 *

 * mm contracts with s390, that even if mm were to remove a page table,

 * racing with the loop below and so causing pte_offset_map_lock() to fail,

 * it will never insert a page table containing empty zero pages once

 * mm_forbids_zeropage(mm) i.e. mm->context.has_pgste is set.

 */

static int __zap_zero_pages(pmd_t *pmd, unsigned long start,

			   unsigned long end, struct mm_walk *walk)
@@ -2549,6 +2554,8 @@ static int __zap_zero_pages(pmd_t *pmd, unsigned long start, 
		spinlock_t *ptl;



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

		if (!ptep)

			break;

		if (is_zero_pfn(pte_pfn(*ptep)))

			ptep_xchg_direct(walk->mm, addr, ptep, __pte(_PAGE_INVALID));

		pte_unmap_unlock(ptep, ptl);

arch/s390/mm/pgtable.c

+9 −3
Original line number Diff line number Diff line
@@ -829,7 +829,7 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr, 
	default:

		return -EFAULT;

	}



again:

	ptl = pmd_lock(mm, pmdp);

	if (!pmd_present(*pmdp)) {

		spin_unlock(ptl);
@@ -850,6 +850,8 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr, 
	spin_unlock(ptl);



	ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);

	if (!ptep)

		goto again;

	new = old = pgste_get_lock(ptep);

	pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT |

			    PGSTE_ACC_BITS | PGSTE_FP_BIT);
@@ -938,7 +940,7 @@ int reset_guest_reference_bit(struct mm_struct *mm, unsigned long addr) 
	default:

		return -EFAULT;

	}



again:

	ptl = pmd_lock(mm, pmdp);

	if (!pmd_present(*pmdp)) {

		spin_unlock(ptl);
@@ -955,6 +957,8 @@ int reset_guest_reference_bit(struct mm_struct *mm, unsigned long addr) 
	spin_unlock(ptl);



	ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);

	if (!ptep)

		goto again;

	new = old = pgste_get_lock(ptep);

	/* Reset guest reference bit only */

	pgste_val(new) &= ~PGSTE_GR_BIT;
@@ -1000,7 +1004,7 @@ int get_guest_storage_key(struct mm_struct *mm, unsigned long addr, 
	default:

		return -EFAULT;

	}



again:

	ptl = pmd_lock(mm, pmdp);

	if (!pmd_present(*pmdp)) {

		spin_unlock(ptl);
@@ -1017,6 +1021,8 @@ int get_guest_storage_key(struct mm_struct *mm, unsigned long addr, 
	spin_unlock(ptl);



	ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl);

	if (!ptep)

		goto again;

	pgste = pgste_get_lock(ptep);

	*key = (pgste_val(pgste) & (PGSTE_ACC_BITS | PGSTE_FP_BIT)) >> 56;

	paddr = pte_val(*ptep) & PAGE_MASK;