linux/arch/sparc/mm/tlb.c
Huang Ying cb9f753a37 mm: fix races between swapoff and flush dcache
Thanks to commit 4b3ef9daa4 ("mm/swap: split swap cache into 64MB
trunks"), after swapoff the address_space associated with the swap
device will be freed.  So page_mapping() users which may touch the
address_space need some kind of mechanism to prevent the address_space
from being freed during accessing.

The dcache flushing functions (flush_dcache_page(), etc) in architecture
specific code may access the address_space of swap device for anonymous
pages in swap cache via page_mapping() function.  But in some cases
there are no mechanisms to prevent the swap device from being swapoff,
for example,

  CPU1					CPU2
  __get_user_pages()			swapoff()
    flush_dcache_page()
      mapping = page_mapping()
        ...				  exit_swap_address_space()
        ...				    kvfree(spaces)
        mapping_mapped(mapping)

The address space may be accessed after being freed.

But from cachetlb.txt and Russell King, flush_dcache_page() only care
about file cache pages, for anonymous pages, flush_anon_page() should be
used.  The implementation of flush_dcache_page() in all architectures
follows this too.  They will check whether page_mapping() is NULL and
whether mapping_mapped() is true to determine whether to flush the
dcache immediately.  And they will use interval tree (mapping->i_mmap)
to find all user space mappings.  While mapping_mapped() and
mapping->i_mmap isn't used by anonymous pages in swap cache at all.

So, to fix the race between swapoff and flush dcache, __page_mapping()
is add to return the address_space for file cache pages and NULL
otherwise.  All page_mapping() invoking in flush dcache functions are
replaced with page_mapping_file().

[akpm@linux-foundation.org: simplify page_mapping_file(), per Mike]
Link: http://lkml.kernel.org/r/20180305083634.15174-1-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Chen Liqin <liqin.linux@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Chris Zankel <chris@zankel.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-05 21:36:26 -07:00

302 lines
6.5 KiB
C

// SPDX-License-Identifier: GPL-2.0
/* arch/sparc64/mm/tlb.c
*
* Copyright (C) 2004 David S. Miller <davem@redhat.com>
*/
#include <linux/kernel.h>
#include <linux/percpu.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/preempt.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include <asm/cacheflush.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>
/* Heavily inspired by the ppc64 code. */
static DEFINE_PER_CPU(struct tlb_batch, tlb_batch);
void flush_tlb_pending(void)
{
struct tlb_batch *tb = &get_cpu_var(tlb_batch);
struct mm_struct *mm = tb->mm;
if (!tb->tlb_nr)
goto out;
flush_tsb_user(tb);
if (CTX_VALID(mm->context)) {
if (tb->tlb_nr == 1) {
global_flush_tlb_page(mm, tb->vaddrs[0]);
} else {
#ifdef CONFIG_SMP
smp_flush_tlb_pending(tb->mm, tb->tlb_nr,
&tb->vaddrs[0]);
#else
__flush_tlb_pending(CTX_HWBITS(tb->mm->context),
tb->tlb_nr, &tb->vaddrs[0]);
#endif
}
}
tb->tlb_nr = 0;
out:
put_cpu_var(tlb_batch);
}
void arch_enter_lazy_mmu_mode(void)
{
struct tlb_batch *tb = this_cpu_ptr(&tlb_batch);
tb->active = 1;
}
void arch_leave_lazy_mmu_mode(void)
{
struct tlb_batch *tb = this_cpu_ptr(&tlb_batch);
if (tb->tlb_nr)
flush_tlb_pending();
tb->active = 0;
}
static void tlb_batch_add_one(struct mm_struct *mm, unsigned long vaddr,
bool exec, unsigned int hugepage_shift)
{
struct tlb_batch *tb = &get_cpu_var(tlb_batch);
unsigned long nr;
vaddr &= PAGE_MASK;
if (exec)
vaddr |= 0x1UL;
nr = tb->tlb_nr;
if (unlikely(nr != 0 && mm != tb->mm)) {
flush_tlb_pending();
nr = 0;
}
if (!tb->active) {
flush_tsb_user_page(mm, vaddr, hugepage_shift);
global_flush_tlb_page(mm, vaddr);
goto out;
}
if (nr == 0) {
tb->mm = mm;
tb->hugepage_shift = hugepage_shift;
}
if (tb->hugepage_shift != hugepage_shift) {
flush_tlb_pending();
tb->hugepage_shift = hugepage_shift;
nr = 0;
}
tb->vaddrs[nr] = vaddr;
tb->tlb_nr = ++nr;
if (nr >= TLB_BATCH_NR)
flush_tlb_pending();
out:
put_cpu_var(tlb_batch);
}
void tlb_batch_add(struct mm_struct *mm, unsigned long vaddr,
pte_t *ptep, pte_t orig, int fullmm,
unsigned int hugepage_shift)
{
if (tlb_type != hypervisor &&
pte_dirty(orig)) {
unsigned long paddr, pfn = pte_pfn(orig);
struct address_space *mapping;
struct page *page;
if (!pfn_valid(pfn))
goto no_cache_flush;
page = pfn_to_page(pfn);
if (PageReserved(page))
goto no_cache_flush;
/* A real file page? */
mapping = page_mapping_file(page);
if (!mapping)
goto no_cache_flush;
paddr = (unsigned long) page_address(page);
if ((paddr ^ vaddr) & (1 << 13))
flush_dcache_page_all(mm, page);
}
no_cache_flush:
if (!fullmm)
tlb_batch_add_one(mm, vaddr, pte_exec(orig), hugepage_shift);
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static void tlb_batch_pmd_scan(struct mm_struct *mm, unsigned long vaddr,
pmd_t pmd)
{
unsigned long end;
pte_t *pte;
pte = pte_offset_map(&pmd, vaddr);
end = vaddr + HPAGE_SIZE;
while (vaddr < end) {
if (pte_val(*pte) & _PAGE_VALID) {
bool exec = pte_exec(*pte);
tlb_batch_add_one(mm, vaddr, exec, PAGE_SHIFT);
}
pte++;
vaddr += PAGE_SIZE;
}
pte_unmap(pte);
}
static void __set_pmd_acct(struct mm_struct *mm, unsigned long addr,
pmd_t orig, pmd_t pmd)
{
if (mm == &init_mm)
return;
if ((pmd_val(pmd) ^ pmd_val(orig)) & _PAGE_PMD_HUGE) {
/*
* Note that this routine only sets pmds for THP pages.
* Hugetlb pages are handled elsewhere. We need to check
* for huge zero page. Huge zero pages are like hugetlb
* pages in that there is no RSS, but there is the need
* for TSB entries. So, huge zero page counts go into
* hugetlb_pte_count.
*/
if (pmd_val(pmd) & _PAGE_PMD_HUGE) {
if (is_huge_zero_page(pmd_page(pmd)))
mm->context.hugetlb_pte_count++;
else
mm->context.thp_pte_count++;
} else {
if (is_huge_zero_page(pmd_page(orig)))
mm->context.hugetlb_pte_count--;
else
mm->context.thp_pte_count--;
}
/* Do not try to allocate the TSB hash table if we
* don't have one already. We have various locks held
* and thus we'll end up doing a GFP_KERNEL allocation
* in an atomic context.
*
* Instead, we let the first TLB miss on a hugepage
* take care of this.
*/
}
if (!pmd_none(orig)) {
addr &= HPAGE_MASK;
if (pmd_trans_huge(orig)) {
pte_t orig_pte = __pte(pmd_val(orig));
bool exec = pte_exec(orig_pte);
tlb_batch_add_one(mm, addr, exec, REAL_HPAGE_SHIFT);
tlb_batch_add_one(mm, addr + REAL_HPAGE_SIZE, exec,
REAL_HPAGE_SHIFT);
} else {
tlb_batch_pmd_scan(mm, addr, orig);
}
}
}
void set_pmd_at(struct mm_struct *mm, unsigned long addr,
pmd_t *pmdp, pmd_t pmd)
{
pmd_t orig = *pmdp;
*pmdp = pmd;
__set_pmd_acct(mm, addr, orig, pmd);
}
static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp, pmd_t pmd)
{
pmd_t old;
do {
old = *pmdp;
} while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd);
__set_pmd_acct(vma->vm_mm, address, old, pmd);
return old;
}
/*
* This routine is only called when splitting a THP
*/
pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp)
{
pmd_t old, entry;
entry = __pmd(pmd_val(*pmdp) & ~_PAGE_VALID);
old = pmdp_establish(vma, address, pmdp, entry);
flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
/*
* set_pmd_at() will not be called in a way to decrement
* thp_pte_count when splitting a THP, so do it now.
* Sanity check pmd before doing the actual decrement.
*/
if ((pmd_val(entry) & _PAGE_PMD_HUGE) &&
!is_huge_zero_page(pmd_page(entry)))
(vma->vm_mm)->context.thp_pte_count--;
return old;
}
void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
pgtable_t pgtable)
{
struct list_head *lh = (struct list_head *) pgtable;
assert_spin_locked(&mm->page_table_lock);
/* FIFO */
if (!pmd_huge_pte(mm, pmdp))
INIT_LIST_HEAD(lh);
else
list_add(lh, (struct list_head *) pmd_huge_pte(mm, pmdp));
pmd_huge_pte(mm, pmdp) = pgtable;
}
pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
{
struct list_head *lh;
pgtable_t pgtable;
assert_spin_locked(&mm->page_table_lock);
/* FIFO */
pgtable = pmd_huge_pte(mm, pmdp);
lh = (struct list_head *) pgtable;
if (list_empty(lh))
pmd_huge_pte(mm, pmdp) = NULL;
else {
pmd_huge_pte(mm, pmdp) = (pgtable_t) lh->next;
list_del(lh);
}
pte_val(pgtable[0]) = 0;
pte_val(pgtable[1]) = 0;
return pgtable;
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */