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Message-Id: <20240917073117.1531207-7-anshuman.khandual@arm.com>
Date: Tue, 17 Sep 2024 13:01:16 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: linux-mm@...ck.org
Cc: Anshuman Khandual <anshuman.khandual@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
David Hildenbrand <david@...hat.com>,
Ryan Roberts <ryan.roberts@....com>,
"Mike Rapoport (IBM)" <rppt@...nel.org>,
Arnd Bergmann <arnd@...db.de>,
x86@...nel.org,
linux-m68k@...ts.linux-m68k.org,
linux-fsdevel@...r.kernel.org,
kasan-dev@...glegroups.com,
linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org,
Dimitri Sivanich <dimitri.sivanich@....com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Muchun Song <muchun.song@...ux.dev>,
Andrey Ryabinin <ryabinin.a.a@...il.com>,
Miaohe Lin <linmiaohe@...wei.com>,
Dennis Zhou <dennis@...nel.org>,
Tejun Heo <tj@...nel.org>,
Christoph Lameter <cl@...ux.com>,
Uladzislau Rezki <urezki@...il.com>,
Christoph Hellwig <hch@...radead.org>
Subject: [PATCH V2 6/7] mm: Use p4dp_get() for accessing P4D entries
Convert P4D accesses via p4dp_get() helper that defaults as READ_ONCE() but
also provides the platform an opportunity to override when required. This
stores read page table entry value in a local variable which can be used in
multiple instances there after. This helps in avoiding multiple memory load
operations as well possible race conditions.
Cc: Dimitri Sivanich <dimitri.sivanich@....com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Muchun Song <muchun.song@...ux.dev>
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc: Miaohe Lin <linmiaohe@...wei.com>
Cc: Dennis Zhou <dennis@...nel.org>
Cc: Tejun Heo <tj@...nel.org>
cc: Christoph Lameter <cl@...ux.com>
Cc: Uladzislau Rezki <urezki@...il.com>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: linux-kernel@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org
Cc: linux-perf-users@...r.kernel.org
Cc: linux-mm@...ck.org
Cc: kasan-dev@...glegroups.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
drivers/misc/sgi-gru/grufault.c | 2 +-
fs/userfaultfd.c | 2 +-
include/linux/pgtable.h | 9 ++++++---
kernel/events/core.c | 2 +-
mm/gup.c | 6 +++---
mm/hugetlb.c | 2 +-
mm/kasan/init.c | 10 +++++-----
mm/kasan/shadow.c | 2 +-
mm/memory-failure.c | 2 +-
mm/memory.c | 16 +++++++++-------
mm/page_vma_mapped.c | 2 +-
mm/percpu.c | 2 +-
mm/pgalloc-track.h | 2 +-
mm/pgtable-generic.c | 2 +-
mm/ptdump.c | 2 +-
mm/rmap.c | 2 +-
mm/sparse-vmemmap.c | 2 +-
mm/vmalloc.c | 15 ++++++++-------
mm/vmscan.c | 2 +-
19 files changed, 45 insertions(+), 39 deletions(-)
diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
index 95d479d5e40f..fcaceac60659 100644
--- a/drivers/misc/sgi-gru/grufault.c
+++ b/drivers/misc/sgi-gru/grufault.c
@@ -216,7 +216,7 @@ static int atomic_pte_lookup(struct vm_area_struct *vma, unsigned long vaddr,
goto err;
p4dp = p4d_offset(pgdp, vaddr);
- if (unlikely(p4d_none(*p4dp)))
+ if (unlikely(p4d_none(p4dp_get(p4dp))))
goto err;
pudp = pud_offset(p4dp, vaddr);
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 00719a0f688c..4044e15cdfd9 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -307,7 +307,7 @@ static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
if (!pgd_present(*pgd))
goto out;
p4d = p4d_offset(pgd, address);
- if (!p4d_present(*p4d))
+ if (!p4d_present(p4dp_get(p4d)))
goto out;
pud = pud_offset(p4d, address);
if (!pud_present(pudp_get(pud)))
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index eb993ef0946f..689cd5a32157 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1081,7 +1081,8 @@ static inline int pgd_same(pgd_t pgd_a, pgd_t pgd_b)
#define set_p4d_safe(p4dp, p4d) \
({ \
- WARN_ON_ONCE(p4d_present(*p4dp) && !p4d_same(*p4dp, p4d)); \
+ p4d_t __old = p4dp_get(p4dp); \
+ WARN_ON_ONCE(p4d_present(__old) && !p4d_same(__old, p4d)); \
set_p4d(p4dp, p4d); \
})
@@ -1251,9 +1252,11 @@ static inline int pgd_none_or_clear_bad(pgd_t *pgd)
static inline int p4d_none_or_clear_bad(p4d_t *p4d)
{
- if (p4d_none(*p4d))
+ p4d_t old_p4d = p4dp_get(p4d);
+
+ if (p4d_none(old_p4d))
return 1;
- if (unlikely(p4d_bad(*p4d))) {
+ if (unlikely(p4d_bad(old_p4d))) {
p4d_clear_bad(p4d);
return 1;
}
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 35e2f2789246..4e56a276ed25 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7611,7 +7611,7 @@ static u64 perf_get_pgtable_size(struct mm_struct *mm, unsigned long addr)
return pgd_leaf_size(pgd);
p4dp = p4d_offset_lockless(pgdp, pgd, addr);
- p4d = READ_ONCE(*p4dp);
+ p4d = p4dp_get(p4dp);
if (!p4d_present(p4d))
return 0;
diff --git a/mm/gup.c b/mm/gup.c
index 300fc7eb306c..3a97d0263052 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1014,7 +1014,7 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,
p4d_t *p4dp, p4d;
p4dp = p4d_offset(pgdp, address);
- p4d = READ_ONCE(*p4dp);
+ p4d = p4dp_get(p4dp);
BUILD_BUG_ON(p4d_leaf(p4d));
if (!p4d_present(p4d) || p4d_bad(p4d))
@@ -1114,7 +1114,7 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address,
if (pgd_none(*pgd))
return -EFAULT;
p4d = p4d_offset(pgd, address);
- if (p4d_none(*p4d))
+ if (p4d_none(p4dp_get(p4d)))
return -EFAULT;
pud = pud_offset(p4d, address);
if (pud_none(pudp_get(pud)))
@@ -3245,7 +3245,7 @@ static int gup_fast_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr,
p4dp = p4d_offset_lockless(pgdp, pgd, addr);
do {
- p4d_t p4d = READ_ONCE(*p4dp);
+ p4d_t p4d = p4dp_get(p4dp);
next = p4d_addr_end(addr, end);
if (!p4d_present(p4d))
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a3820242b01e..4fdb91c8cc2b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7454,7 +7454,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
if (!pgd_present(*pgd))
return NULL;
p4d = p4d_offset(pgd, addr);
- if (!p4d_present(*p4d))
+ if (!p4d_present(p4dp_get(p4d)))
return NULL;
pud = pud_offset(p4d, addr);
diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index f4cf519443e1..02af738fee5e 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -208,7 +208,7 @@ static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
continue;
}
- if (p4d_none(*p4d)) {
+ if (p4d_none(p4dp_get(p4d))) {
pud_t *p;
if (slab_is_available()) {
@@ -330,7 +330,7 @@ static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
return;
}
- pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
+ pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(p4dp_get(p4d))));
p4d_clear(p4d);
}
@@ -341,7 +341,7 @@ static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
for (i = 0; i < PTRS_PER_P4D; i++) {
p4d = p4d_start + i;
- if (!p4d_none(*p4d))
+ if (!p4d_none(p4dp_get(p4d)))
return;
}
@@ -434,10 +434,10 @@ static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
next = p4d_addr_end(addr, end);
- if (!p4d_present(*p4d))
+ if (!p4d_present(p4dp_get(p4d)))
continue;
- if (kasan_pud_table(*p4d)) {
+ if (kasan_pud_table(p4dp_get(p4d))) {
if (IS_ALIGNED(addr, P4D_SIZE) &&
IS_ALIGNED(next, P4D_SIZE)) {
p4d_clear(p4d);
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index dbd8164c75f1..52150cc5ae5f 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -194,7 +194,7 @@ static bool shadow_mapped(unsigned long addr)
if (pgd_none(*pgd))
return false;
p4d = p4d_offset(pgd, addr);
- if (p4d_none(*p4d))
+ if (p4d_none(p4dp_get(p4d)))
return false;
pud = pud_offset(p4d, addr);
if (pud_none(pudp_get(pud)))
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index fbb63401fb51..3d900cc039b3 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -414,7 +414,7 @@ static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
if (!pgd_present(*pgd))
return 0;
p4d = p4d_offset(pgd, address);
- if (!p4d_present(*p4d))
+ if (!p4d_present(p4dp_get(p4d)))
return 0;
pud = pud_offset(p4d, address);
if (!pud_present(pudp_get(pud)))
diff --git a/mm/memory.c b/mm/memory.c
index 801750e4337c..5056f39f2c3b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2906,7 +2906,7 @@ static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd,
pte_fn_t fn, void *data, bool create,
pgtbl_mod_mask *mask)
{
- p4d_t *p4d;
+ p4d_t *p4d, old_p4d;
unsigned long next;
int err = 0;
@@ -2919,11 +2919,12 @@ static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd,
}
do {
next = p4d_addr_end(addr, end);
- if (p4d_none(*p4d) && !create)
+ old_p4d = p4dp_get(p4d);
+ if (p4d_none(old_p4d) && !create)
continue;
- if (WARN_ON_ONCE(p4d_leaf(*p4d)))
+ if (WARN_ON_ONCE(p4d_leaf(old_p4d)))
return -EINVAL;
- if (!p4d_none(*p4d) && WARN_ON_ONCE(p4d_bad(*p4d))) {
+ if (!p4d_none(old_p4d) && WARN_ON_ONCE(p4d_bad(old_p4d))) {
if (!create)
continue;
p4d_clear_bad(p4d);
@@ -6075,7 +6076,7 @@ int __pud_alloc(struct mm_struct *mm, p4d_t *p4d, unsigned long address)
return -ENOMEM;
spin_lock(&mm->page_table_lock);
- if (!p4d_present(*p4d)) {
+ if (!p4d_present(p4dp_get(p4d))) {
mm_inc_nr_puds(mm);
smp_wmb(); /* See comment in pmd_install() */
p4d_populate(mm, p4d, new);
@@ -6143,7 +6144,7 @@ int follow_pte(struct vm_area_struct *vma, unsigned long address,
{
struct mm_struct *mm = vma->vm_mm;
pgd_t *pgd;
- p4d_t *p4d;
+ p4d_t *p4d, old_p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *ptep;
@@ -6160,7 +6161,8 @@ int follow_pte(struct vm_area_struct *vma, unsigned long address,
goto out;
p4d = p4d_offset(pgd, address);
- if (p4d_none(*p4d) || unlikely(p4d_bad(*p4d)))
+ old_p4d = p4dp_get(p4d);
+ if (p4d_none(old_p4d) || unlikely(p4d_bad(old_p4d)))
goto out;
pud = pud_offset(p4d, address);
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 511266307771..a33f92db2666 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -217,7 +217,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
continue;
}
p4d = p4d_offset(pgd, pvmw->address);
- if (!p4d_present(*p4d)) {
+ if (!p4d_present(p4dp_get(p4d))) {
step_forward(pvmw, P4D_SIZE);
continue;
}
diff --git a/mm/percpu.c b/mm/percpu.c
index 5f32164b04a2..58660e8eb892 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -3192,7 +3192,7 @@ void __init __weak pcpu_populate_pte(unsigned long addr)
}
p4d = p4d_offset(pgd, addr);
- if (p4d_none(*p4d)) {
+ if (p4d_none(p4dp_get(p4d))) {
pud = memblock_alloc(PUD_TABLE_SIZE, PUD_TABLE_SIZE);
if (!pud)
goto err_alloc;
diff --git a/mm/pgalloc-track.h b/mm/pgalloc-track.h
index 0f6b809431a3..3db8ccbcb141 100644
--- a/mm/pgalloc-track.h
+++ b/mm/pgalloc-track.h
@@ -20,7 +20,7 @@ static inline pud_t *pud_alloc_track(struct mm_struct *mm, p4d_t *p4d,
unsigned long address,
pgtbl_mod_mask *mod_mask)
{
- if (unlikely(p4d_none(*p4d))) {
+ if (unlikely(p4d_none(p4dp_get(p4d)))) {
if (__pud_alloc(mm, p4d, address))
return NULL;
*mod_mask |= PGTBL_P4D_MODIFIED;
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index e09e3f920f7a..f5ab52beb536 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -31,7 +31,7 @@ void pgd_clear_bad(pgd_t *pgd)
#ifndef __PAGETABLE_P4D_FOLDED
void p4d_clear_bad(p4d_t *p4d)
{
- p4d_ERROR(*p4d);
+ p4d_ERROR(p4dp_get(p4d));
p4d_clear(p4d);
}
#endif
diff --git a/mm/ptdump.c b/mm/ptdump.c
index 32ae8e829329..2c40224b8ad0 100644
--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -53,7 +53,7 @@ static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
unsigned long next, struct mm_walk *walk)
{
struct ptdump_state *st = walk->private;
- p4d_t val = READ_ONCE(*p4d);
+ p4d_t val = p4dp_get(p4d);
#if CONFIG_PGTABLE_LEVELS > 3 && \
(defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
diff --git a/mm/rmap.c b/mm/rmap.c
index 81f1946653e0..a0ff325467eb 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -813,7 +813,7 @@ pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
goto out;
p4d = p4d_offset(pgd, address);
- if (!p4d_present(*p4d))
+ if (!p4d_present(p4dp_get(p4d)))
goto out;
pud = pud_offset(p4d, address);
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index d8ea64ec665f..2bd1c95f107a 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -220,7 +220,7 @@ void __weak __meminit pud_init(void *addr)
p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node)
{
p4d_t *p4d = p4d_offset(pgd, addr);
- if (p4d_none(*p4d)) {
+ if (p4d_none(p4dp_get(p4d))) {
void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
if (!p)
return NULL;
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 05292d998122..f27ecac7bd6e 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -251,7 +251,7 @@ static int vmap_try_huge_p4d(p4d_t *p4d, unsigned long addr, unsigned long end,
if (!IS_ALIGNED(phys_addr, P4D_SIZE))
return 0;
- if (p4d_present(*p4d) && !p4d_free_pud_page(p4d, addr))
+ if (p4d_present(p4dp_get(p4d)) && !p4d_free_pud_page(p4d, addr))
return 0;
return p4d_set_huge(p4d, phys_addr, prot);
@@ -418,7 +418,7 @@ static void vunmap_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
next = p4d_addr_end(addr, end);
p4d_clear_huge(p4d);
- if (p4d_bad(*p4d))
+ if (p4d_bad(p4dp_get(p4d)))
*mask |= PGTBL_P4D_MODIFIED;
if (p4d_none_or_clear_bad(p4d))
@@ -741,7 +741,7 @@ struct page *vmalloc_to_page(const void *vmalloc_addr)
unsigned long addr = (unsigned long) vmalloc_addr;
struct page *page = NULL;
pgd_t *pgd = pgd_offset_k(addr);
- p4d_t *p4d;
+ p4d_t *p4d, old_p4d;
pud_t *pud, old_pud;
pmd_t *pmd, old_pmd;
pte_t *ptep, pte;
@@ -760,11 +760,12 @@ struct page *vmalloc_to_page(const void *vmalloc_addr)
return NULL;
p4d = p4d_offset(pgd, addr);
- if (p4d_none(*p4d))
+ old_p4d = p4dp_get(p4d);
+ if (p4d_none(old_p4d))
return NULL;
- if (p4d_leaf(*p4d))
- return p4d_page(*p4d) + ((addr & ~P4D_MASK) >> PAGE_SHIFT);
- if (WARN_ON_ONCE(p4d_bad(*p4d)))
+ if (p4d_leaf(old_p4d))
+ return p4d_page(old_p4d) + ((addr & ~P4D_MASK) >> PAGE_SHIFT);
+ if (WARN_ON_ONCE(p4d_bad(old_p4d)))
return NULL;
pud = pud_offset(p4d, addr);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 04b03e6c3095..b16925b5f072 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3579,7 +3579,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end,
unsigned long next;
struct lru_gen_mm_walk *walk = args->private;
- VM_WARN_ON_ONCE(p4d_leaf(*p4d));
+ VM_WARN_ON_ONCE(p4d_leaf(p4dp_get(p4d)));
pud = pud_offset(p4d, start & P4D_MASK);
restart:
--
2.25.1
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