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mm: introduce __vm_flags_mod and use it in untrack_pfn
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There are scenarios when vm_flags can be modified without exclusive
mmap_lock, such as:
- after VMA was isolated and mmap_lock was downgraded or dropped
- in exit_mmap when there are no other mm users and locking is unnecessary
Introduce __vm_flags_mod to avoid assertions when the caller takes
responsibility for the required locking.
Pass a hint to untrack_pfn to conditionally use __vm_flags_mod for
flags modification to avoid assertion.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Suren Baghdasaryan <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Mike Rapoport (IBM) <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arjun Roy <[email protected]>
Cc: Axel Rasmussen <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: David Howells <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Greg Thelen <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: Laurent Dufour <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Oskolkov <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Punit Agrawal <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Sebastian Reichel <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Soheil Hassas Yeganeh <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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surenbaghdasaryan authored and akpm00 committed Feb 10, 2023
1 parent ff126c0 commit 68f4838
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Showing 6 changed files with 41 additions and 21 deletions.
10 changes: 7 additions & 3 deletions arch/x86/mm/pat/memtype.c
Original file line number Diff line number Diff line change
Expand Up @@ -1046,7 +1046,7 @@ void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, pfn_t pfn)
* can be for the entire vma (in which case pfn, size are zero).
*/
void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
unsigned long size)
unsigned long size, bool mm_wr_locked)
{
resource_size_t paddr;
unsigned long prot;
Expand All @@ -1065,8 +1065,12 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
size = vma->vm_end - vma->vm_start;
}
free_pfn_range(paddr, size);
if (vma)
vm_flags_clear(vma, VM_PAT);
if (vma) {
if (mm_wr_locked)
vm_flags_clear(vma, VM_PAT);
else
__vm_flags_mod(vma, 0, VM_PAT);
}
}

/*
Expand Down
14 changes: 12 additions & 2 deletions include/linux/mm.h
Original file line number Diff line number Diff line change
Expand Up @@ -656,6 +656,16 @@ static inline void vm_flags_clear(struct vm_area_struct *vma,
ACCESS_PRIVATE(vma, __vm_flags) &= ~flags;
}

/*
* Use only if VMA is not part of the VMA tree or has no other users and
* therefore needs no locking.
*/
static inline void __vm_flags_mod(struct vm_area_struct *vma,
vm_flags_t set, vm_flags_t clear)
{
vm_flags_init(vma, (vma->vm_flags | set) & ~clear);
}

/*
* Use only when the order of set/clear operations is unimportant, otherwise
* use vm_flags_{set|clear} explicitly.
Expand All @@ -664,7 +674,7 @@ static inline void vm_flags_mod(struct vm_area_struct *vma,
vm_flags_t set, vm_flags_t clear)
{
mmap_assert_write_locked(vma->vm_mm);
vm_flags_init(vma, (vma->vm_flags | set) & ~clear);
__vm_flags_mod(vma, set, clear);
}

static inline void vma_set_anonymous(struct vm_area_struct *vma)
Expand Down Expand Up @@ -2085,7 +2095,7 @@ static inline void zap_vma_pages(struct vm_area_struct *vma)
}
void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
struct vm_area_struct *start_vma, unsigned long start,
unsigned long end);
unsigned long end, bool mm_wr_locked);

struct mmu_notifier_range;

Expand Down
5 changes: 3 additions & 2 deletions include/linux/pgtable.h
Original file line number Diff line number Diff line change
Expand Up @@ -1185,7 +1185,8 @@ static inline int track_pfn_copy(struct vm_area_struct *vma)
* can be for the entire vma (in which case pfn, size are zero).
*/
static inline void untrack_pfn(struct vm_area_struct *vma,
unsigned long pfn, unsigned long size)
unsigned long pfn, unsigned long size,
bool mm_wr_locked)
{
}

Expand All @@ -1203,7 +1204,7 @@ extern void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
pfn_t pfn);
extern int track_pfn_copy(struct vm_area_struct *vma);
extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
unsigned long size);
unsigned long size, bool mm_wr_locked);
extern void untrack_pfn_moved(struct vm_area_struct *vma);
#endif

Expand Down
13 changes: 7 additions & 6 deletions mm/memory.c
Original file line number Diff line number Diff line change
Expand Up @@ -1613,7 +1613,7 @@ void unmap_page_range(struct mmu_gather *tlb,
static void unmap_single_vma(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long start_addr,
unsigned long end_addr,
struct zap_details *details)
struct zap_details *details, bool mm_wr_locked)
{
unsigned long start = max(vma->vm_start, start_addr);
unsigned long end;
Expand All @@ -1628,7 +1628,7 @@ static void unmap_single_vma(struct mmu_gather *tlb,
uprobe_munmap(vma, start, end);

if (unlikely(vma->vm_flags & VM_PFNMAP))
untrack_pfn(vma, 0, 0);
untrack_pfn(vma, 0, 0, mm_wr_locked);

if (start != end) {
if (unlikely(is_vm_hugetlb_page(vma))) {
Expand Down Expand Up @@ -1675,7 +1675,7 @@ static void unmap_single_vma(struct mmu_gather *tlb,
*/
void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
struct vm_area_struct *vma, unsigned long start_addr,
unsigned long end_addr)
unsigned long end_addr, bool mm_wr_locked)
{
struct mmu_notifier_range range;
struct zap_details details = {
Expand All @@ -1689,7 +1689,8 @@ void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
start_addr, end_addr);
mmu_notifier_invalidate_range_start(&range);
do {
unmap_single_vma(tlb, vma, start_addr, end_addr, &details);
unmap_single_vma(tlb, vma, start_addr, end_addr, &details,
mm_wr_locked);
} while ((vma = mas_find(&mas, end_addr - 1)) != NULL);
mmu_notifier_invalidate_range_end(&range);
}
Expand Down Expand Up @@ -1723,7 +1724,7 @@ void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
* unmap 'address-end' not 'range.start-range.end' as range
* could have been expanded for hugetlb pmd sharing.
*/
unmap_single_vma(&tlb, vma, address, end, details);
unmap_single_vma(&tlb, vma, address, end, details, false);
mmu_notifier_invalidate_range_end(&range);
tlb_finish_mmu(&tlb);
}
Expand Down Expand Up @@ -2492,7 +2493,7 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,

err = remap_pfn_range_notrack(vma, addr, pfn, size, prot);
if (err)
untrack_pfn(vma, pfn, PAGE_ALIGN(size));
untrack_pfn(vma, pfn, PAGE_ALIGN(size), true);
return err;
}
EXPORT_SYMBOL(remap_pfn_range);
Expand Down
4 changes: 2 additions & 2 deletions mm/memremap.c
Original file line number Diff line number Diff line change
Expand Up @@ -129,7 +129,7 @@ static void pageunmap_range(struct dev_pagemap *pgmap, int range_id)
}
mem_hotplug_done();

untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range));
untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range), true);
pgmap_array_delete(range);
}

Expand Down Expand Up @@ -276,7 +276,7 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
if (!is_private)
kasan_remove_zero_shadow(__va(range->start), range_len(range));
err_kasan:
untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range));
untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range), true);
err_pfn_remap:
pgmap_array_delete(range);
return error;
Expand Down
16 changes: 10 additions & 6 deletions mm/mmap.c
Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@ core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
struct vm_area_struct *vma, struct vm_area_struct *prev,
struct vm_area_struct *next, unsigned long start,
unsigned long end);
unsigned long end, bool mm_wr_locked);

static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
{
Expand Down Expand Up @@ -2133,14 +2133,14 @@ static inline void remove_mt(struct mm_struct *mm, struct ma_state *mas)
static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
struct vm_area_struct *vma, struct vm_area_struct *prev,
struct vm_area_struct *next,
unsigned long start, unsigned long end)
unsigned long start, unsigned long end, bool mm_wr_locked)
{
struct mmu_gather tlb;

lru_add_drain();
tlb_gather_mmu(&tlb, mm);
update_hiwater_rss(mm);
unmap_vmas(&tlb, mt, vma, start, end);
unmap_vmas(&tlb, mt, vma, start, end, mm_wr_locked);
free_pgtables(&tlb, mt, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
next ? next->vm_start : USER_PGTABLES_CEILING);
tlb_finish_mmu(&tlb);
Expand Down Expand Up @@ -2388,7 +2388,11 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
mmap_write_downgrade(mm);
}

unmap_region(mm, &mt_detach, vma, prev, next, start, end);
/*
* We can free page tables without write-locking mmap_lock because VMAs
* were isolated before we downgraded mmap_lock.
*/
unmap_region(mm, &mt_detach, vma, prev, next, start, end, !downgrade);
/* Statistics and freeing VMAs */
mas_set(&mas_detach, start);
remove_mt(mm, &mas_detach);
Expand Down Expand Up @@ -2701,7 +2705,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,

/* Undo any partial mapping done by a device driver. */
unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start,
vma->vm_end);
vma->vm_end, true);
}
if (file && (vm_flags & VM_SHARED))
mapping_unmap_writable(file->f_mapping);
Expand Down Expand Up @@ -3029,7 +3033,7 @@ void exit_mmap(struct mm_struct *mm)
tlb_gather_mmu_fullmm(&tlb, mm);
/* update_hiwater_rss(mm) here? but nobody should be looking */
/* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */
unmap_vmas(&tlb, &mm->mm_mt, vma, 0, ULONG_MAX);
unmap_vmas(&tlb, &mm->mm_mt, vma, 0, ULONG_MAX, false);
mmap_read_unlock(mm);

/*
Expand Down

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