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mm: madvise: use per_vma lock for MADV_FREE

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MADV_FREE is another option, besides MADV_DONTNEED, for dynamic memory
freeing in user-space native or Java heap memory management.  For example,
jemalloc can be configured to use MADV_FREE, and recent versions of the
Android Java heap have also increasingly adopted MADV_FREE.  Supporting
per-VMA locking for MADV_FREE thus appears increasingly necessary.

We have replaced walk_page_range() with walk_page_range_vma().  Along with
the proposed madvise_lock_mode by Lorenzo, the necessary infrastructure is
now in place to begin exploring per-VMA locking support for MADV_FREE and
potentially other madvise using walk_page_range_vma().

This patch adds support for the PGWALK_VMA_RDLOCK walk_lock mode in
walk_page_range_vma(), and leverages madvise_lock_mode from madv_behavior
to select the appropriate walk_lock—either mmap_lock or per-VMA
lock—based on the context.

Because we now dynamically update the walk_ops->walk_lock field, we must
ensure this is thread-safe.  The madvise_free_walk_ops is now defined as a
stack variable instead of a global constant.

Link: https://lkml.kernel.org/r/20250611104745.57405-1-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: SeongJae Park <sj@kernel.org>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Tangquan Zheng <zhengtangquan@oppo.com>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Barry Song
2025-06-11 22:47:45 +12:00
committed by Andrew Morton
parent f822a9a81a
commit 4f8ba33bbd
3 changed files with 25 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/pagewalk.h
View File

@@ -14,6 +14,8 @@ enum page_walk_lock {
PGWALK_WRLOCK = 1,
/* vma is expected to be already write-locked during the walk */
PGWALK_WRLOCK_VERIFY = 2,
/* vma is expected to be already read-locked during the walk */
PGWALK_VMA_RDLOCK_VERIFY = 3,
};
/**

25
mm/madvise.c
View File

@@ -777,10 +777,19 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
return 0;
}
static const struct mm_walk_ops madvise_free_walk_ops = {
.pmd_entry = madvise_free_pte_range,
.walk_lock = PGWALK_RDLOCK,
};
static inline enum page_walk_lock get_walk_lock(enum madvise_lock_mode mode)
{
switch (mode) {
case MADVISE_VMA_READ_LOCK:
return PGWALK_VMA_RDLOCK_VERIFY;
case MADVISE_MMAP_READ_LOCK:
return PGWALK_RDLOCK;
default:
/* Other modes don't require fixing up the walk_lock */
WARN_ON_ONCE(1);
return PGWALK_RDLOCK;
}
}
static int madvise_free_single_vma(struct madvise_behavior *madv_behavior,
struct vm_area_struct *vma,
@@ -789,6 +798,9 @@ static int madvise_free_single_vma(struct madvise_behavior *madv_behavior,
struct mm_struct *mm = vma->vm_mm;
struct mmu_notifier_range range;
struct mmu_gather *tlb = madv_behavior->tlb;
struct mm_walk_ops walk_ops = {
.pmd_entry = madvise_free_pte_range,
};
/* MADV_FREE works for only anon vma at the moment */
if (!vma_is_anonymous(vma))
@@ -808,8 +820,9 @@ static int madvise_free_single_vma(struct madvise_behavior *madv_behavior,
mmu_notifier_invalidate_range_start(&range);
tlb_start_vma(tlb, vma);
walk_ops.walk_lock = get_walk_lock(madv_behavior->lock_mode);
walk_page_range_vma(vma, range.start, range.end,
&madvise_free_walk_ops, tlb);
&walk_ops, tlb);
tlb_end_vma(tlb, vma);
mmu_notifier_invalidate_range_end(&range);
return 0;
@@ -1658,7 +1671,6 @@ static enum madvise_lock_mode get_lock_mode(struct madvise_behavior *madv_behavi
case MADV_WILLNEED:
case MADV_COLD:
case MADV_PAGEOUT:
case MADV_FREE:
case MADV_POPULATE_READ:
case MADV_POPULATE_WRITE:
case MADV_COLLAPSE:
@@ -1667,6 +1679,7 @@ static enum madvise_lock_mode get_lock_mode(struct madvise_behavior *madv_behavi
return MADVISE_MMAP_READ_LOCK;
case MADV_DONTNEED:
case MADV_DONTNEED_LOCKED:
case MADV_FREE:
return MADVISE_VMA_READ_LOCK;
default:
return MADVISE_MMAP_WRITE_LOCK;

5
mm/pagewalk.c
View File

@@ -422,7 +422,7 @@ static inline void process_mm_walk_lock(struct mm_struct *mm,
{
if (walk_lock == PGWALK_RDLOCK)
mmap_assert_locked(mm);
else
else if (walk_lock != PGWALK_VMA_RDLOCK_VERIFY)
mmap_assert_write_locked(mm);
}
@@ -437,6 +437,9 @@ static inline void process_vma_walk_lock(struct vm_area_struct *vma,
case PGWALK_WRLOCK_VERIFY:
vma_assert_write_locked(vma);
break;
case PGWALK_VMA_RDLOCK_VERIFY:
vma_assert_locked(vma);
break;
case PGWALK_RDLOCK:
/* PGWALK_RDLOCK is handled by process_mm_walk_lock */
break;