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mm: enable page walking API to lock vmas during the walk 

walk_page_range() and friends often operate under write-locked mmap_lock. 
With introduction of vma locks, the vmas have to be locked as well during
such walks to prevent concurrent page faults in these areas.  Add an
additional member to mm_walk_ops to indicate locking requirements for the
walk.

The change ensures that page walks which prevent concurrent page faults
by write-locking mmap_lock, operate correctly after introduction of
per-vma locks.  With per-vma locks page faults can be handled under vma
lock without taking mmap_lock at all, so write locking mmap_lock would
not stop them.  The change ensures vmas are properly locked during such
walks.

A sample issue this solves is do_mbind() performing queue_pages_range()
to queue pages for migration.  Without this change a concurrent page
can be faulted into the area and be left out of migration.

Link: https://lkml.kernel.org/r/20230804152724.3090321-2-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Suggested-by: Jann Horn <jannh@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michel Lespinasse <michel@lespinasse.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Suren Baghdasaryan 2023-08-04 08:27:19 -07:00 committed by Andrew Morton
parent 8b9c1cc041
commit 49b0638502
18 changed files with 100 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/powerpc/mm/book3s64/subpage_prot.c
View File

@ -145,6 +145,7 @@ static int subpage_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
static const struct mm_walk_ops subpage_walk_ops = {
.pmd_entry = subpage_walk_pmd_entry,
.walk_lock = PGWALK_WRLOCK_VERIFY,
};
static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,

1
arch/riscv/mm/pageattr.c
View File

@ -102,6 +102,7 @@ static const struct mm_walk_ops pageattr_ops = {
.pmd_entry = pageattr_pmd_entry,
.pte_entry = pageattr_pte_entry,
.pte_hole = pageattr_pte_hole,
.walk_lock = PGWALK_RDLOCK,
};
static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask,

5
arch/s390/mm/gmap.c
View File

@ -2514,6 +2514,7 @@ static int thp_split_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
static const struct mm_walk_ops thp_split_walk_ops = {
.pmd_entry = thp_split_walk_pmd_entry,
.walk_lock = PGWALK_WRLOCK_VERIFY,
};
static inline void thp_split_mm(struct mm_struct *mm)
@ -2565,6 +2566,7 @@ static int __zap_zero_pages(pmd_t *pmd, unsigned long start,
static const struct mm_walk_ops zap_zero_walk_ops = {
.pmd_entry = __zap_zero_pages,
.walk_lock = PGWALK_WRLOCK,
};
/*
@ -2655,6 +2657,7 @@ static const struct mm_walk_ops enable_skey_walk_ops = {
.hugetlb_entry = __s390_enable_skey_hugetlb,
.pte_entry = __s390_enable_skey_pte,
.pmd_entry = __s390_enable_skey_pmd,
.walk_lock = PGWALK_WRLOCK,
};
int s390_enable_skey(void)
@ -2692,6 +2695,7 @@ static int __s390_reset_cmma(pte_t *pte, unsigned long addr,
static const struct mm_walk_ops reset_cmma_walk_ops = {
.pte_entry = __s390_reset_cmma,
.walk_lock = PGWALK_WRLOCK,
};
void s390_reset_cmma(struct mm_struct *mm)
@ -2728,6 +2732,7 @@ static int s390_gather_pages(pte_t *ptep, unsigned long addr,
static const struct mm_walk_ops gather_pages_ops = {
.pte_entry = s390_gather_pages,
.walk_lock = PGWALK_RDLOCK,
};
/*

5
fs/proc/task_mmu.c
View File

@ -757,12 +757,14 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
static const struct mm_walk_ops smaps_walk_ops = {
.pmd_entry = smaps_pte_range,
.hugetlb_entry = smaps_hugetlb_range,
.walk_lock = PGWALK_RDLOCK,
};
static const struct mm_walk_ops smaps_shmem_walk_ops = {
.pmd_entry = smaps_pte_range,
.hugetlb_entry = smaps_hugetlb_range,
.pte_hole = smaps_pte_hole,
.walk_lock = PGWALK_RDLOCK,
};
/*
@ -1244,6 +1246,7 @@ static int clear_refs_test_walk(unsigned long start, unsigned long end,
static const struct mm_walk_ops clear_refs_walk_ops = {
.pmd_entry = clear_refs_pte_range,
.test_walk = clear_refs_test_walk,
.walk_lock = PGWALK_WRLOCK,
};
static ssize_t clear_refs_write(struct file *file, const char __user *buf,
@ -1621,6 +1624,7 @@ static const struct mm_walk_ops pagemap_ops = {
.pmd_entry = pagemap_pmd_range,
.pte_hole = pagemap_pte_hole,
.hugetlb_entry = pagemap_hugetlb_range,
.walk_lock = PGWALK_RDLOCK,
};
/*
@ -1934,6 +1938,7 @@ static int gather_hugetlb_stats(pte_t *pte, unsigned long hmask,
static const struct mm_walk_ops show_numa_ops = {
.hugetlb_entry = gather_hugetlb_stats,
.pmd_entry = gather_pte_stats,
.walk_lock = PGWALK_RDLOCK,
};
/*

11
include/linux/pagewalk.h
View File

@ -6,6 +6,16 @@
struct mm_walk;
/* Locking requirement during a page walk. */
enum page_walk_lock {
/* mmap_lock should be locked for read to stabilize the vma tree */
PGWALK_RDLOCK = 0,
/* vma will be write-locked during the walk */
PGWALK_WRLOCK = 1,
/* vma is expected to be already write-locked during the walk */
PGWALK_WRLOCK_VERIFY = 2,
};
/**
* struct mm_walk_ops - callbacks for walk_page_range
* @pgd_entry: if set, called for each non-empty PGD (top-level) entry
@ -66,6 +76,7 @@ struct mm_walk_ops {
int (*pre_vma)(unsigned long start, unsigned long end,
struct mm_walk *walk);
void (*post_vma)(struct mm_walk *walk);
enum page_walk_lock walk_lock;
};
/*

2
mm/damon/vaddr.c
View File

@ -386,6 +386,7 @@ out:
static const struct mm_walk_ops damon_mkold_ops = {
.pmd_entry = damon_mkold_pmd_entry,
.hugetlb_entry = damon_mkold_hugetlb_entry,
.walk_lock = PGWALK_RDLOCK,
};
static void damon_va_mkold(struct mm_struct *mm, unsigned long addr)
@ -525,6 +526,7 @@ out:
static const struct mm_walk_ops damon_young_ops = {
.pmd_entry = damon_young_pmd_entry,
.hugetlb_entry = damon_young_hugetlb_entry,
.walk_lock = PGWALK_RDLOCK,
};
static bool damon_va_young(struct mm_struct *mm, unsigned long addr,

1
mm/hmm.c
View File

@ -562,6 +562,7 @@ static const struct mm_walk_ops hmm_walk_ops = {
.pte_hole = hmm_vma_walk_hole,
.hugetlb_entry = hmm_vma_walk_hugetlb_entry,
.test_walk = hmm_vma_walk_test,
.walk_lock = PGWALK_RDLOCK,
};
/**

25
mm/ksm.c
View File

@ -455,6 +455,12 @@ static int break_ksm_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long nex
static const struct mm_walk_ops break_ksm_ops = {
.pmd_entry = break_ksm_pmd_entry,
.walk_lock = PGWALK_RDLOCK,
};
static const struct mm_walk_ops break_ksm_lock_vma_ops = {
.pmd_entry = break_ksm_pmd_entry,
.walk_lock = PGWALK_WRLOCK,
};
/*
@ -470,16 +476,17 @@ static const struct mm_walk_ops break_ksm_ops = {
* of the process that owns 'vma'. We also do not want to enforce
* protection keys here anyway.
*/
static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
static int break_ksm(struct vm_area_struct *vma, unsigned long addr, bool lock_vma)
{
vm_fault_t ret = 0;
const struct mm_walk_ops *ops = lock_vma ?
&break_ksm_lock_vma_ops : &break_ksm_ops;
do {
int ksm_page;
cond_resched();
ksm_page = walk_page_range_vma(vma, addr, addr + 1,
&break_ksm_ops, NULL);
ksm_page = walk_page_range_vma(vma, addr, addr + 1, ops, NULL);
if (WARN_ON_ONCE(ksm_page < 0))
return ksm_page;
if (!ksm_page)
@ -565,7 +572,7 @@ static void break_cow(struct ksm_rmap_item *rmap_item)
mmap_read_lock(mm);
vma = find_mergeable_vma(mm, addr);
if (vma)
break_ksm(vma, addr);
break_ksm(vma, addr, false);
mmap_read_unlock(mm);
}
@ -871,7 +878,7 @@ static void remove_trailing_rmap_items(struct ksm_rmap_item **rmap_list)
* in cmp_and_merge_page on one of the rmap_items we would be removing.
*/
static int unmerge_ksm_pages(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
unsigned long start, unsigned long end, bool lock_vma)
{
unsigned long addr;
int err = 0;
@ -882,7 +889,7 @@ static int unmerge_ksm_pages(struct vm_area_struct *vma,
if (signal_pending(current))
err = -ERESTARTSYS;
else
err = break_ksm(vma, addr);
err = break_ksm(vma, addr, lock_vma);
}
return err;
}
@ -1029,7 +1036,7 @@ static int unmerge_and_remove_all_rmap_items(void)
if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
continue;
err = unmerge_ksm_pages(vma,
vma->vm_start, vma->vm_end);
vma->vm_start, vma->vm_end, false);
if (err)
goto error;
}
@ -2530,7 +2537,7 @@ static int __ksm_del_vma(struct vm_area_struct *vma)
return 0;
if (vma->anon_vma) {
err = unmerge_ksm_pages(vma, vma->vm_start, vma->vm_end);
err = unmerge_ksm_pages(vma, vma->vm_start, vma->vm_end, true);
if (err)
return err;
}
@ -2668,7 +2675,7 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
return 0; /* just ignore the advice */
if (vma->anon_vma) {
err = unmerge_ksm_pages(vma, start, end);
err = unmerge_ksm_pages(vma, start, end, true);
if (err)
return err;
}

3
mm/madvise.c
View File

@ -233,6 +233,7 @@ static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
static const struct mm_walk_ops swapin_walk_ops = {
.pmd_entry = swapin_walk_pmd_entry,
.walk_lock = PGWALK_RDLOCK,
};
static void shmem_swapin_range(struct vm_area_struct *vma,
@ -534,6 +535,7 @@ regular_folio:
static const struct mm_walk_ops cold_walk_ops = {
.pmd_entry = madvise_cold_or_pageout_pte_range,
.walk_lock = PGWALK_RDLOCK,
};
static void madvise_cold_page_range(struct mmu_gather *tlb,
@ -757,6 +759,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
static const struct mm_walk_ops madvise_free_walk_ops = {
.pmd_entry = madvise_free_pte_range,
.walk_lock = PGWALK_RDLOCK,
};
static int madvise_free_single_vma(struct vm_area_struct *vma,

2
mm/memcontrol.c
View File

@ -6024,6 +6024,7 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
static const struct mm_walk_ops precharge_walk_ops = {
.pmd_entry = mem_cgroup_count_precharge_pte_range,
.walk_lock = PGWALK_RDLOCK,
};
static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
@ -6303,6 +6304,7 @@ put: /* get_mctgt_type() gets & locks the page */
static const struct mm_walk_ops charge_walk_ops = {
.pmd_entry = mem_cgroup_move_charge_pte_range,
.walk_lock = PGWALK_RDLOCK,
};
static void mem_cgroup_move_charge(void)

1
mm/memory-failure.c
View File

@ -831,6 +831,7 @@ static int hwpoison_hugetlb_range(pte_t *ptep, unsigned long hmask,
static const struct mm_walk_ops hwp_walk_ops = {
.pmd_entry = hwpoison_pte_range,
.hugetlb_entry = hwpoison_hugetlb_range,
.walk_lock = PGWALK_RDLOCK,
};
/*

22
mm/mempolicy.c
View File

@ -718,6 +718,14 @@ static const struct mm_walk_ops queue_pages_walk_ops = {
.hugetlb_entry = queue_folios_hugetlb,
.pmd_entry = queue_folios_pte_range,
.test_walk = queue_pages_test_walk,
.walk_lock = PGWALK_RDLOCK,
};
static const struct mm_walk_ops queue_pages_lock_vma_walk_ops = {
.hugetlb_entry = queue_folios_hugetlb,
.pmd_entry = queue_folios_pte_range,
.test_walk = queue_pages_test_walk,
.walk_lock = PGWALK_WRLOCK,
};
/*
@ -738,7 +746,7 @@ static const struct mm_walk_ops queue_pages_walk_ops = {
static int
queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,
nodemask_t *nodes, unsigned long flags,
struct list_head *pagelist)
struct list_head *pagelist, bool lock_vma)
{
int err;
struct queue_pages qp = {
@ -749,8 +757,10 @@ queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,
.end = end,
.first = NULL,
};
const struct mm_walk_ops *ops = lock_vma ?
&queue_pages_lock_vma_walk_ops : &queue_pages_walk_ops;
err = walk_page_range(mm, start, end, &queue_pages_walk_ops, &qp);
err = walk_page_range(mm, start, end, ops, &qp);
if (!qp.first)
/* whole range in hole */
@ -1078,7 +1088,7 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
vma = find_vma(mm, 0);
VM_BUG_ON(!(flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)));
queue_pages_range(mm, vma->vm_start, mm->task_size, &nmask,
flags | MPOL_MF_DISCONTIG_OK, &pagelist);
flags | MPOL_MF_DISCONTIG_OK, &pagelist, false);
if (!list_empty(&pagelist)) {
err = migrate_pages(&pagelist, alloc_migration_target, NULL,
@ -1321,12 +1331,8 @@ static long do_mbind(unsigned long start, unsigned long len,
* Lock the VMAs before scanning for pages to migrate, to ensure we don't
* miss a concurrently inserted page.
*/
vma_iter_init(&vmi, mm, start);
for_each_vma_range(vmi, vma, end)
vma_start_write(vma);
ret = queue_pages_range(mm, start, end, nmask,
flags | MPOL_MF_INVERT, &pagelist);
flags | MPOL_MF_INVERT, &pagelist, true);
if (ret < 0) {
err = ret;

1
mm/migrate_device.c
View File

@ -279,6 +279,7 @@ next:
static const struct mm_walk_ops migrate_vma_walk_ops = {
.pmd_entry = migrate_vma_collect_pmd,
.pte_hole = migrate_vma_collect_hole,
.walk_lock = PGWALK_RDLOCK,
};
/*

1
mm/mincore.c
View File

@ -176,6 +176,7 @@ static const struct mm_walk_ops mincore_walk_ops = {
.pmd_entry = mincore_pte_range,
.pte_hole = mincore_unmapped_range,
.hugetlb_entry = mincore_hugetlb,
.walk_lock = PGWALK_RDLOCK,
};
/*

1
mm/mlock.c
View File

@ -371,6 +371,7 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma,
{
static const struct mm_walk_ops mlock_walk_ops = {
.pmd_entry = mlock_pte_range,
.walk_lock = PGWALK_WRLOCK_VERIFY,
};
/*

1
mm/mprotect.c
View File

@ -568,6 +568,7 @@ static const struct mm_walk_ops prot_none_walk_ops = {
.pte_entry = prot_none_pte_entry,
.hugetlb_entry = prot_none_hugetlb_entry,
.test_walk = prot_none_test,
.walk_lock = PGWALK_WRLOCK,
};
int

36
mm/pagewalk.c
View File

@ -400,6 +400,33 @@ static int __walk_page_range(unsigned long start, unsigned long end,
return err;
}
static inline void process_mm_walk_lock(struct mm_struct *mm,
enum page_walk_lock walk_lock)
{
if (walk_lock == PGWALK_RDLOCK)
mmap_assert_locked(mm);
else
mmap_assert_write_locked(mm);
}
static inline void process_vma_walk_lock(struct vm_area_struct *vma,
enum page_walk_lock walk_lock)
{
#ifdef CONFIG_PER_VMA_LOCK
switch (walk_lock) {
case PGWALK_WRLOCK:
vma_start_write(vma);
break;
case PGWALK_WRLOCK_VERIFY:
vma_assert_write_locked(vma);
break;
case PGWALK_RDLOCK:
/* PGWALK_RDLOCK is handled by process_mm_walk_lock */
break;
}
#endif
}
/**
* walk_page_range - walk page table with caller specific callbacks
* @mm: mm_struct representing the target process of page table walk
@ -459,7 +486,7 @@ int walk_page_range(struct mm_struct *mm, unsigned long start,
if (!walk.mm)
return -EINVAL;
mmap_assert_locked(walk.mm);
process_mm_walk_lock(walk.mm, ops->walk_lock);
vma = find_vma(walk.mm, start);
do {
@ -474,6 +501,7 @@ int walk_page_range(struct mm_struct *mm, unsigned long start,
if (ops->pte_hole)
err = ops->pte_hole(start, next, -1, &walk);
} else { /* inside vma */
process_vma_walk_lock(vma, ops->walk_lock);
walk.vma = vma;
next = min(end, vma->vm_end);
vma = find_vma(mm, vma->vm_end);
@ -549,7 +577,8 @@ int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start,
if (start < vma->vm_start || end > vma->vm_end)
return -EINVAL;
mmap_assert_locked(walk.mm);
process_mm_walk_lock(walk.mm, ops->walk_lock);
process_vma_walk_lock(vma, ops->walk_lock);
return __walk_page_range(start, end, &walk);
}
@ -566,7 +595,8 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
if (!walk.mm)
return -EINVAL;
mmap_assert_locked(walk.mm);
process_mm_walk_lock(walk.mm, ops->walk_lock);
process_vma_walk_lock(vma, ops->walk_lock);
return __walk_page_range(vma->vm_start, vma->vm_end, &walk);
}

1
mm/vmscan.c
View File

@ -4284,6 +4284,7 @@ static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_
static const struct mm_walk_ops mm_walk_ops = {
.test_walk = should_skip_vma,
.p4d_entry = walk_pud_range,
.walk_lock = PGWALK_RDLOCK,
};
int err;