On Mon, Sep 15, 2025 at 09:36:35AM -0700, Kalesh Singh wrote:
> A mechanical rename of the mm_struct->map_count field to
> vma_count; no functional change is intended.
>
> The name "map_count" is ambiguous within the memory management subsystem,
> as it can be confused with the folio/page->_mapcount field, which tracks
> PTE references.
>
> The new name, vma_count, is more precise as this field has always
> counted the number of vm_area_structs associated with an mm_struct.
>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: David Hildenbrand <da...@redhat.com>
> Cc: "Liam R. Howlett" <liam.howl...@oracle.com>
> Cc: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
> Cc: Mike Rapoport <r...@kernel.org>
> Cc: Minchan Kim <minc...@kernel.org>
> Cc: Pedro Falcato <pfalc...@suse.de>
> Signed-off-by: Kalesh Singh <kaleshsi...@google.com>
Yeah this is nice thanks, LGTM so:
Reviewed-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
One small comment below, but I think that change can wait for another series
probably.
> ---
>
> Changes in v2:
> - map_count is easily confused with _mapcount rename to vma_count, per David
>
> fs/binfmt_elf.c | 2 +-
> fs/coredump.c | 2 +-
> include/linux/mm_types.h | 2 +-
> kernel/fork.c | 2 +-
> mm/debug.c | 2 +-
> mm/mmap.c | 6 +++---
> mm/nommu.c | 6 +++---
> mm/vma.c | 24 ++++++++++++------------
> tools/testing/vma/vma.c | 32 ++++++++++++++++----------------
> tools/testing/vma/vma_internal.h | 6 +++---
> 10 files changed, 42 insertions(+), 42 deletions(-)
>
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 264fba0d44bd..52449dec12cb 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1643,7 +1643,7 @@ static int fill_files_note(struct memelfnote *note,
> struct coredump_params *cprm
> data[0] = count;
> data[1] = PAGE_SIZE;
> /*
> - * Count usually is less than mm->map_count,
> + * Count usually is less than mm->vma_count,
> * we need to move filenames down.
> */
> n = cprm->vma_count - count;
> diff --git a/fs/coredump.c b/fs/coredump.c
> index 60bc9685e149..8881459c53d9 100644
> --- a/fs/coredump.c
> +++ b/fs/coredump.c
> @@ -1731,7 +1731,7 @@ static bool dump_vma_snapshot(struct coredump_params
> *cprm)
>
> cprm->vma_data_size = 0;
> gate_vma = get_gate_vma(mm);
> - cprm->vma_count = mm->map_count + (gate_vma ? 1 : 0);
> + cprm->vma_count = mm->vma_count + (gate_vma ? 1 : 0);
>
> cprm->vma_meta = kvmalloc_array(cprm->vma_count,
> sizeof(*cprm->vma_meta), GFP_KERNEL);
> if (!cprm->vma_meta) {
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 08bc2442db93..4343be2f9e85 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -1020,7 +1020,7 @@ struct mm_struct {
> #ifdef CONFIG_MMU
> atomic_long_t pgtables_bytes; /* size of all page tables */
> #endif
> - int map_count; /* number of VMAs */
> + int vma_count; /* number of VMAs */
>
> spinlock_t page_table_lock; /* Protects page tables and some
> * counters
> diff --git a/kernel/fork.c b/kernel/fork.c
> index c4ada32598bd..8fcbbf947579 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1037,7 +1037,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm,
> struct task_struct *p,
> mmap_init_lock(mm);
> INIT_LIST_HEAD(&mm->mmlist);
> mm_pgtables_bytes_init(mm);
> - mm->map_count = 0;
> + mm->vma_count = 0;
> mm->locked_vm = 0;
> atomic64_set(&mm->pinned_vm, 0);
> memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
> diff --git a/mm/debug.c b/mm/debug.c
> index b4388f4dcd4d..40fc9425a84a 100644
> --- a/mm/debug.c
> +++ b/mm/debug.c
> @@ -204,7 +204,7 @@ void dump_mm(const struct mm_struct *mm)
> mm->pgd, atomic_read(&mm->mm_users),
> atomic_read(&mm->mm_count),
> mm_pgtables_bytes(mm),
> - mm->map_count,
> + mm->vma_count,
> mm->hiwater_rss, mm->hiwater_vm, mm->total_vm, mm->locked_vm,
> (u64)atomic64_read(&mm->pinned_vm),
> mm->data_vm, mm->exec_vm, mm->stack_vm,
> diff --git a/mm/mmap.c b/mm/mmap.c
> index af88ce1fbb5f..c6769394a174 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1308,7 +1308,7 @@ void exit_mmap(struct mm_struct *mm)
> vma = vma_next(&vmi);
> } while (vma && likely(!xa_is_zero(vma)));
>
> - BUG_ON(count != mm->map_count);
> + BUG_ON(count != mm->vma_count);
Be nice to switch this to a WARN_ON_ONCE()... think David mentioned it though.
But maybe not one for this series...
>
> trace_exit_mmap(mm);
> destroy:
> @@ -1517,7 +1517,7 @@ static int sysctl_max_map_count __read_mostly =
> DEFAULT_MAX_MAP_COUNT;
> */
> int vma_count_remaining(const struct mm_struct *mm)
> {
> - const int map_count = mm->map_count;
> + const int map_count = mm->vma_count;
> const int max_count = sysctl_max_map_count;
>
> return (max_count > map_count) ? (max_count - map_count) : 0;
> @@ -1828,7 +1828,7 @@ __latent_entropy int dup_mmap(struct mm_struct *mm,
> struct mm_struct *oldmm)
> */
> vma_iter_bulk_store(&vmi, tmp);
>
> - mm->map_count++;
> + mm->vma_count++;
>
> if (tmp->vm_ops && tmp->vm_ops->open)
> tmp->vm_ops->open(tmp);
> diff --git a/mm/nommu.c b/mm/nommu.c
> index dd75f2334812..9ab2e5ca736d 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -576,7 +576,7 @@ static void setup_vma_to_mm(struct vm_area_struct *vma,
> struct mm_struct *mm)
>
> static void cleanup_vma_from_mm(struct vm_area_struct *vma)
> {
> - vma->vm_mm->map_count--;
> + vma->vm_mm->vma_count--;
> /* remove the VMA from the mapping */
> if (vma->vm_file) {
> struct address_space *mapping;
> @@ -1198,7 +1198,7 @@ unsigned long do_mmap(struct file *file,
> goto error_just_free;
>
> setup_vma_to_mm(vma, current->mm);
> - current->mm->map_count++;
> + current->mm->vma_count++;
> /* add the VMA to the tree */
> vma_iter_store_new(&vmi, vma);
>
> @@ -1366,7 +1366,7 @@ static int split_vma(struct vma_iterator *vmi, struct
> vm_area_struct *vma,
> setup_vma_to_mm(vma, mm);
> setup_vma_to_mm(new, mm);
> vma_iter_store_new(vmi, new);
> - mm->map_count++;
> + mm->vma_count++;
> return 0;
>
> err_vmi_preallocate:
> diff --git a/mm/vma.c b/mm/vma.c
> index df0e8409f63d..64f4e7c867c3 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -352,7 +352,7 @@ static void vma_complete(struct vma_prepare *vp, struct
> vma_iterator *vmi,
> * (it may either follow vma or precede it).
> */
> vma_iter_store_new(vmi, vp->insert);
> - mm->map_count++;
> + mm->vma_count++;
> }
>
> if (vp->anon_vma) {
> @@ -383,7 +383,7 @@ static void vma_complete(struct vma_prepare *vp, struct
> vma_iterator *vmi,
> }
> if (vp->remove->anon_vma)
> anon_vma_merge(vp->vma, vp->remove);
> - mm->map_count--;
> + mm->vma_count--;
> mpol_put(vma_policy(vp->remove));
> if (!vp->remove2)
> WARN_ON_ONCE(vp->vma->vm_end < vp->remove->vm_end);
> @@ -683,13 +683,13 @@ void validate_mm(struct mm_struct *mm)
> }
> #endif
> /* Check for a infinite loop */
> - if (++i > mm->map_count + 10) {
> + if (++i > mm->vma_count + 10) {
> i = -1;
> break;
> }
> }
> - if (i != mm->map_count) {
> - pr_emerg("map_count %d vma iterator %d\n", mm->map_count, i);
> + if (i != mm->vma_count) {
> + pr_emerg("vma_count %d vma iterator %d\n", mm->vma_count, i);
> bug = 1;
> }
> VM_BUG_ON_MM(bug, mm);
> @@ -1266,7 +1266,7 @@ static void vms_complete_munmap_vmas(struct
> vma_munmap_struct *vms,
> struct mm_struct *mm;
>
> mm = current->mm;
> - mm->map_count -= vms->vma_count;
> + mm->vma_count -= vms->vma_count;
> mm->locked_vm -= vms->locked_vm;
> if (vms->unlock)
> mmap_write_downgrade(mm);
> @@ -1340,14 +1340,14 @@ static int vms_gather_munmap_vmas(struct
> vma_munmap_struct *vms,
> if (vms->start > vms->vma->vm_start) {
>
> /*
> - * Make sure that map_count on return from munmap() will
> + * Make sure that vma_count on return from munmap() will
> * not exceed its limit; but let map_count go just above
> * its limit temporarily, to help free resources as expected.
> */
> if (vms->end < vms->vma->vm_end &&
> !vma_count_remaining(vms->vma->vm_mm)) {
> error = -ENOMEM;
> - goto map_count_exceeded;
> + goto vma_count_exceeded;
> }
>
> /* Don't bother splitting the VMA if we can't unmap it anyway */
> @@ -1461,7 +1461,7 @@ static int vms_gather_munmap_vmas(struct
> vma_munmap_struct *vms,
> modify_vma_failed:
> reattach_vmas(mas_detach);
> start_split_failed:
> -map_count_exceeded:
> +vma_count_exceeded:
> return error;
> }
>
> @@ -1795,7 +1795,7 @@ int vma_link(struct mm_struct *mm, struct
> vm_area_struct *vma)
> vma_start_write(vma);
> vma_iter_store_new(&vmi, vma);
> vma_link_file(vma);
> - mm->map_count++;
> + mm->vma_count++;
> validate_mm(mm);
> return 0;
> }
> @@ -2495,7 +2495,7 @@ static int __mmap_new_vma(struct mmap_state *map,
> struct vm_area_struct **vmap)
> /* Lock the VMA since it is modified after insertion into VMA tree */
> vma_start_write(vma);
> vma_iter_store_new(vmi, vma);
> - map->mm->map_count++;
> + map->mm->vma_count++;
> vma_link_file(vma);
>
> /*
> @@ -2810,7 +2810,7 @@ int do_brk_flags(struct vma_iterator *vmi, struct
> vm_area_struct *vma,
> if (vma_iter_store_gfp(vmi, vma, GFP_KERNEL))
> goto mas_store_fail;
>
> - mm->map_count++;
> + mm->vma_count++;
> validate_mm(mm);
> out:
> perf_event_mmap(vma);
> diff --git a/tools/testing/vma/vma.c b/tools/testing/vma/vma.c
> index 656e1c75b711..69fa7d14a6c2 100644
> --- a/tools/testing/vma/vma.c
> +++ b/tools/testing/vma/vma.c
> @@ -261,7 +261,7 @@ static int cleanup_mm(struct mm_struct *mm, struct
> vma_iterator *vmi)
> }
>
> mtree_destroy(&mm->mm_mt);
> - mm->map_count = 0;
> + mm->vma_count = 0;
> return count;
> }
>
> @@ -500,7 +500,7 @@ static bool test_merge_new(void)
> INIT_LIST_HEAD(&vma_d->anon_vma_chain);
> list_add(&dummy_anon_vma_chain_d.same_vma, &vma_d->anon_vma_chain);
> ASSERT_FALSE(merged);
> - ASSERT_EQ(mm.map_count, 4);
> + ASSERT_EQ(mm.vma_count, 4);
>
> /*
> * Merge BOTH sides.
> @@ -519,7 +519,7 @@ static bool test_merge_new(void)
> ASSERT_EQ(vma->vm_pgoff, 0);
> ASSERT_EQ(vma->anon_vma, &dummy_anon_vma);
> ASSERT_TRUE(vma_write_started(vma));
> - ASSERT_EQ(mm.map_count, 3);
> + ASSERT_EQ(mm.vma_count, 3);
>
> /*
> * Merge to PREVIOUS VMA.
> @@ -536,7 +536,7 @@ static bool test_merge_new(void)
> ASSERT_EQ(vma->vm_pgoff, 0);
> ASSERT_EQ(vma->anon_vma, &dummy_anon_vma);
> ASSERT_TRUE(vma_write_started(vma));
> - ASSERT_EQ(mm.map_count, 3);
> + ASSERT_EQ(mm.vma_count, 3);
>
> /*
> * Merge to NEXT VMA.
> @@ -555,7 +555,7 @@ static bool test_merge_new(void)
> ASSERT_EQ(vma->vm_pgoff, 6);
> ASSERT_EQ(vma->anon_vma, &dummy_anon_vma);
> ASSERT_TRUE(vma_write_started(vma));
> - ASSERT_EQ(mm.map_count, 3);
> + ASSERT_EQ(mm.vma_count, 3);
>
> /*
> * Merge BOTH sides.
> @@ -573,7 +573,7 @@ static bool test_merge_new(void)
> ASSERT_EQ(vma->vm_pgoff, 0);
> ASSERT_EQ(vma->anon_vma, &dummy_anon_vma);
> ASSERT_TRUE(vma_write_started(vma));
> - ASSERT_EQ(mm.map_count, 2);
> + ASSERT_EQ(mm.vma_count, 2);
>
> /*
> * Merge to NEXT VMA.
> @@ -591,7 +591,7 @@ static bool test_merge_new(void)
> ASSERT_EQ(vma->vm_pgoff, 0xa);
> ASSERT_EQ(vma->anon_vma, &dummy_anon_vma);
> ASSERT_TRUE(vma_write_started(vma));
> - ASSERT_EQ(mm.map_count, 2);
> + ASSERT_EQ(mm.vma_count, 2);
>
> /*
> * Merge BOTH sides.
> @@ -608,7 +608,7 @@ static bool test_merge_new(void)
> ASSERT_EQ(vma->vm_pgoff, 0);
> ASSERT_EQ(vma->anon_vma, &dummy_anon_vma);
> ASSERT_TRUE(vma_write_started(vma));
> - ASSERT_EQ(mm.map_count, 1);
> + ASSERT_EQ(mm.vma_count, 1);
>
> /*
> * Final state.
> @@ -967,7 +967,7 @@ static bool test_vma_merge_new_with_close(void)
> ASSERT_EQ(vma->vm_pgoff, 0);
> ASSERT_EQ(vma->vm_ops, &vm_ops);
> ASSERT_TRUE(vma_write_started(vma));
> - ASSERT_EQ(mm.map_count, 2);
> + ASSERT_EQ(mm.vma_count, 2);
>
> cleanup_mm(&mm, &vmi);
> return true;
> @@ -1017,7 +1017,7 @@ static bool test_merge_existing(void)
> ASSERT_EQ(vma->vm_pgoff, 2);
> ASSERT_TRUE(vma_write_started(vma));
> ASSERT_TRUE(vma_write_started(vma_next));
> - ASSERT_EQ(mm.map_count, 2);
> + ASSERT_EQ(mm.vma_count, 2);
>
> /* Clear down and reset. */
> ASSERT_EQ(cleanup_mm(&mm, &vmi), 2);
> @@ -1045,7 +1045,7 @@ static bool test_merge_existing(void)
> ASSERT_EQ(vma_next->vm_pgoff, 2);
> ASSERT_EQ(vma_next->anon_vma, &dummy_anon_vma);
> ASSERT_TRUE(vma_write_started(vma_next));
> - ASSERT_EQ(mm.map_count, 1);
> + ASSERT_EQ(mm.vma_count, 1);
>
> /* Clear down and reset. We should have deleted vma. */
> ASSERT_EQ(cleanup_mm(&mm, &vmi), 1);
> @@ -1079,7 +1079,7 @@ static bool test_merge_existing(void)
> ASSERT_EQ(vma->vm_pgoff, 6);
> ASSERT_TRUE(vma_write_started(vma_prev));
> ASSERT_TRUE(vma_write_started(vma));
> - ASSERT_EQ(mm.map_count, 2);
> + ASSERT_EQ(mm.vma_count, 2);
>
> /* Clear down and reset. */
> ASSERT_EQ(cleanup_mm(&mm, &vmi), 2);
> @@ -1108,7 +1108,7 @@ static bool test_merge_existing(void)
> ASSERT_EQ(vma_prev->vm_pgoff, 0);
> ASSERT_EQ(vma_prev->anon_vma, &dummy_anon_vma);
> ASSERT_TRUE(vma_write_started(vma_prev));
> - ASSERT_EQ(mm.map_count, 1);
> + ASSERT_EQ(mm.vma_count, 1);
>
> /* Clear down and reset. We should have deleted vma. */
> ASSERT_EQ(cleanup_mm(&mm, &vmi), 1);
> @@ -1138,7 +1138,7 @@ static bool test_merge_existing(void)
> ASSERT_EQ(vma_prev->vm_pgoff, 0);
> ASSERT_EQ(vma_prev->anon_vma, &dummy_anon_vma);
> ASSERT_TRUE(vma_write_started(vma_prev));
> - ASSERT_EQ(mm.map_count, 1);
> + ASSERT_EQ(mm.vma_count, 1);
>
> /* Clear down and reset. We should have deleted prev and next. */
> ASSERT_EQ(cleanup_mm(&mm, &vmi), 1);
> @@ -1540,7 +1540,7 @@ static bool test_merge_extend(void)
> ASSERT_EQ(vma->vm_end, 0x4000);
> ASSERT_EQ(vma->vm_pgoff, 0);
> ASSERT_TRUE(vma_write_started(vma));
> - ASSERT_EQ(mm.map_count, 1);
> + ASSERT_EQ(mm.vma_count, 1);
>
> cleanup_mm(&mm, &vmi);
> return true;
> @@ -1652,7 +1652,7 @@ static bool test_mmap_region_basic(void)
> 0x24d, NULL);
> ASSERT_EQ(addr, 0x24d000);
>
> - ASSERT_EQ(mm.map_count, 2);
> + ASSERT_EQ(mm.vma_count, 2);
>
> for_each_vma(vmi, vma) {
> if (vma->vm_start == 0x300000) {
> diff --git a/tools/testing/vma/vma_internal.h
> b/tools/testing/vma/vma_internal.h
> index 52cd7ddc73f4..15525b86145d 100644
> --- a/tools/testing/vma/vma_internal.h
> +++ b/tools/testing/vma/vma_internal.h
> @@ -251,7 +251,7 @@ struct mutex {};
>
> struct mm_struct {
> struct maple_tree mm_mt;
> - int map_count; /* number of VMAs */
> + int vma_count; /* number of VMAs */
> unsigned long total_vm; /* Total pages mapped */
> unsigned long locked_vm; /* Pages that have PG_mlocked set */
> unsigned long data_vm; /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
> @@ -1520,10 +1520,10 @@ static inline vm_flags_t ksm_vma_flags(const struct
> mm_struct *, const struct fi
> /* Helper to get VMA count capacity */
> static int vma_count_remaining(const struct mm_struct *mm)
> {
> - const int map_count = mm->map_count;
> + const int vma_count = mm->vma_count;
> const int max_count = sysctl_max_map_count;
>
> - return (max_count > map_count) ? (max_count - map_count) : 0;
> + return (max_count > vma_count) ? (max_count - vma_count) : 0;
> }
>
> #endif /* __MM_VMA_INTERNAL_H */
> --
> 2.51.0.384.g4c02a37b29-goog
>
