Re: [PATCH v2 06/13] mm: update hugetlbfs to use VMA flags on mmap_prepare

Liam R. Howlett
2026-02-09T19:04:38Z

* Lorenzo Stoakes <lorenzo.stoakes@oracle.com> [260122 16:06]:
> In order to update all mmap_prepare users to utilising the new VMA flags
> type vma_flags_t and associated helper functions, we start by updating
> hugetlbfs which has a lot of additional logic that requires updating to
> make this change.
>
> This is laying the groundwork for eliminating the vm_flags_t from struct
> vm_area_desc and using vma_flags_t only, which further lays the ground for
> removing the deprecated vm_flags_t type altogether.
>
> No functional changes intended.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

> ---
> fs/hugetlbfs/inode.c | 14 +++++++-------
> include/linux/hugetlb.h | 6 +++---
> include/linux/hugetlb_inline.h | 10 ++++++++++
> ipc/shm.c | 12 +++++++-----
> mm/hugetlb.c | 22 +++++++++++-----------
> mm/memfd.c | 4 ++--
> mm/mmap.c | 2 +-
> 7 files changed, 41 insertions(+), 29 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 3b4c152c5c73..95a5b23b4808 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -109,7 +109,7 @@ static int hugetlbfs_file_mmap_prepare(struct vm_area_desc *desc)
> loff_t len, vma_len;
> int ret;
> struct hstate *h = hstate_file(file);
> - vm_flags_t vm_flags;
> + vma_flags_t vma_flags;
>
> /*
> * vma address alignment (but not the pgoff alignment) has
> @@ -119,7 +119,7 @@ static int hugetlbfs_file_mmap_prepare(struct vm_area_desc *desc)
> * way when do_mmap unwinds (may be important on powerpc
> * and ia64).
> */
> - desc->vm_flags |= VM_HUGETLB | VM_DONTEXPAND;
> + vma_desc_set_flags(desc, VMA_HUGETLB_BIT, VMA_DONTEXPAND_BIT);
> desc->vm_ops = &hugetlb_vm_ops;
>
> /*
> @@ -148,23 +148,23 @@ static int hugetlbfs_file_mmap_prepare(struct vm_area_desc *desc)
>
> ret = -ENOMEM;
>
> - vm_flags = desc->vm_flags;
> + vma_flags = desc->vma_flags;
> /*
> * for SHM_HUGETLB, the pages are reserved in the shmget() call so skip
> * reserving here. Note: only for SHM hugetlbfs file, the inode
> * flag S_PRIVATE is set.
> */
> if (inode->i_flags & S_PRIVATE)
> - vm_flags |= VM_NORESERVE;
> + vma_flags_set(&vma_flags, VMA_NORESERVE_BIT);
>
> if (hugetlb_reserve_pages(inode,
> desc->pgoff >> huge_page_order(h),
> len >> huge_page_shift(h), desc,
> - vm_flags) < 0)
> + vma_flags) < 0)
> goto out;
>
> ret = 0;
> - if ((desc->vm_flags & VM_WRITE) && inode->i_size < len)
> + if (vma_desc_test_flags(desc, VMA_WRITE_BIT) && inode->i_size < len)
> i_size_write(inode, len);
> out:
> inode_unlock(inode);
> @@ -1527,7 +1527,7 @@ static int get_hstate_idx(int page_size_log)
> * otherwise hugetlb_reserve_pages reserves one less hugepages than intended.
> */
> struct file *hugetlb_file_setup(const char *name, size_t size,
> - vm_flags_t acctflag, int creat_flags,
> + vma_flags_t acctflag, int creat_flags,
> int page_size_log)
> {
> struct inode *inode;
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 94a03591990c..4e72bf66077e 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -150,7 +150,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
> struct folio **foliop);
> #endif /* CONFIG_USERFAULTFD */
> long hugetlb_reserve_pages(struct inode *inode, long from, long to,
> - struct vm_area_desc *desc, vm_flags_t vm_flags);
> + struct vm_area_desc *desc, vma_flags_t vma_flags);
> long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
> long freed);
> bool folio_isolate_hugetlb(struct folio *folio, struct list_head *list);
> @@ -529,7 +529,7 @@ static inline struct hugetlbfs_inode_info *HUGETLBFS_I(struct inode *inode)
> }
>
> extern const struct vm_operations_struct hugetlb_vm_ops;
> -struct file *hugetlb_file_setup(const char *name, size_t size, vm_flags_t acct,
> +struct file *hugetlb_file_setup(const char *name, size_t size, vma_flags_t acct,
> int creat_flags, int page_size_log);
>
> static inline bool is_file_hugepages(const struct file *file)
> @@ -545,7 +545,7 @@ static inline struct hstate *hstate_inode(struct inode *i)
>
> #define is_file_hugepages(file) false
> static inline struct file *
> -hugetlb_file_setup(const char *name, size_t size, vm_flags_t acctflag,
> +hugetlb_file_setup(const char *name, size_t size, vma_flags_t acctflag,
> int creat_flags, int page_size_log)
> {
> return ERR_PTR(-ENOSYS);
> diff --git a/include/linux/hugetlb_inline.h b/include/linux/hugetlb_inline.h
> index a27aa0162918..593f5d4e108b 100644
> --- a/include/linux/hugetlb_inline.h
> +++ b/include/linux/hugetlb_inline.h
> @@ -11,6 +11,11 @@ static inline bool is_vm_hugetlb_flags(vm_flags_t vm_flags)
> return !!(vm_flags & VM_HUGETLB);
> }
>
> +static inline bool is_vma_hugetlb_flags(const vma_flags_t *flags)
> +{
> + return vma_flags_test(flags, VMA_HUGETLB_BIT);
> +}
> +
> #else
>
> static inline bool is_vm_hugetlb_flags(vm_flags_t vm_flags)
> @@ -18,6 +23,11 @@ static inline bool is_vm_hugetlb_flags(vm_flags_t vm_flags)
> return false;
> }
>
> +static inline bool is_vma_hugetlb_flags(const vma_flags_t *flags)
> +{
> + return false;
> +}
> +
> #endif
>
> static inline bool is_vm_hugetlb_page(struct vm_area_struct *vma)
> diff --git a/ipc/shm.c b/ipc/shm.c
> index 3db36773dd10..2c7379c4c647 100644
> --- a/ipc/shm.c
> +++ b/ipc/shm.c
> @@ -707,9 +707,9 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
> int error;
> struct shmid_kernel *shp;
> size_t numpages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
> + const bool has_no_reserve = shmflg & SHM_NORESERVE;
> struct file *file;
> char name[13];
> - vm_flags_t acctflag = 0;
>
> if (size < SHMMIN || size > ns->shm_ctlmax)
> return -EINVAL;
> @@ -738,6 +738,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
>
> sprintf(name, "SYSV%08x", key);
> if (shmflg & SHM_HUGETLB) {
> + vma_flags_t acctflag = EMPTY_VMA_FLAGS;
> struct hstate *hs;
> size_t hugesize;
>
> @@ -749,17 +750,18 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
> hugesize = ALIGN(size, huge_page_size(hs));
>
> /* hugetlb_file_setup applies strict accounting */
> - if (shmflg & SHM_NORESERVE)
> - acctflag = VM_NORESERVE;
> + if (has_no_reserve)
> + vma_flags_set(&acctflag, VMA_NORESERVE_BIT);
> file = hugetlb_file_setup(name, hugesize, acctflag,
> HUGETLB_SHMFS_INODE, (shmflg >> SHM_HUGE_SHIFT) & SHM_HUGE_MASK);
> } else {
> + vm_flags_t acctflag = 0;
> +
> /*
> * Do not allow no accounting for OVERCOMMIT_NEVER, even
> * if it's asked for.
> */
> - if ((shmflg & SHM_NORESERVE) &&
> - sysctl_overcommit_memory != OVERCOMMIT_NEVER)
> + if (has_no_reserve && sysctl_overcommit_memory != OVERCOMMIT_NEVER)
> acctflag = VM_NORESERVE;
> file = shmem_kernel_file_setup(name, size, acctflag);
> }
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 4f4494251f5c..e6955061d751 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1193,16 +1193,16 @@ static void set_vma_resv_flags(struct vm_area_struct *vma, unsigned long flags)
>
> static void set_vma_desc_resv_map(struct vm_area_desc *desc, struct resv_map *map)
> {
> - VM_WARN_ON_ONCE(!is_vm_hugetlb_flags(desc->vm_flags));
> - VM_WARN_ON_ONCE(desc->vm_flags & VM_MAYSHARE);
> + VM_WARN_ON_ONCE(!is_vma_hugetlb_flags(&desc->vma_flags));
> + VM_WARN_ON_ONCE(vma_desc_test_flags(desc, VMA_MAYSHARE_BIT));
>
> desc->private_data = map;
> }
>
> static void set_vma_desc_resv_flags(struct vm_area_desc *desc, unsigned long flags)
> {
> - VM_WARN_ON_ONCE(!is_vm_hugetlb_flags(desc->vm_flags));
> - VM_WARN_ON_ONCE(desc->vm_flags & VM_MAYSHARE);
> + VM_WARN_ON_ONCE(!is_vma_hugetlb_flags(&desc->vma_flags));
> + VM_WARN_ON_ONCE(vma_desc_test_flags(desc, VMA_MAYSHARE_BIT));
>
> desc->private_data = (void *)((unsigned long)desc->private_data | flags);
> }
> @@ -1216,7 +1216,7 @@ static int is_vma_resv_set(struct vm_area_struct *vma, unsigned long flag)
>
> static bool is_vma_desc_resv_set(struct vm_area_desc *desc, unsigned long flag)
> {
> - VM_WARN_ON_ONCE(!is_vm_hugetlb_flags(desc->vm_flags));
> + VM_WARN_ON_ONCE(!is_vma_hugetlb_flags(&desc->vma_flags));
>
> return ((unsigned long)desc->private_data) & flag;
> }
> @@ -6564,7 +6564,7 @@ long hugetlb_change_protection(struct vm_area_struct *vma,
> long hugetlb_reserve_pages(struct inode *inode,
> long from, long to,
> struct vm_area_desc *desc,
> - vm_flags_t vm_flags)
> + vma_flags_t vma_flags)
> {
> long chg = -1, add = -1, spool_resv, gbl_resv;
> struct hstate *h = hstate_inode(inode);
> @@ -6585,7 +6585,7 @@ long hugetlb_reserve_pages(struct inode *inode,
> * attempt will be made for VM_NORESERVE to allocate a page
> * without using reserves
> */
> - if (vm_flags & VM_NORESERVE)
> + if (vma_flags_test(&vma_flags, VMA_NORESERVE_BIT))
> return 0;
>
> /*
> @@ -6594,7 +6594,7 @@ long hugetlb_reserve_pages(struct inode *inode,
> * to reserve the full area even if read-only as mprotect() may be
> * called to make the mapping read-write. Assume !desc is a shm mapping
> */
> - if (!desc || desc->vm_flags & VM_MAYSHARE) {
> + if (!desc || vma_desc_test_flags(desc, VMA_MAYSHARE_BIT)) {
> /*
> * resv_map can not be NULL as hugetlb_reserve_pages is only
> * called for inodes for which resv_maps were created (see
> @@ -6628,7 +6628,7 @@ long hugetlb_reserve_pages(struct inode *inode,
> if (err < 0)
> goto out_err;
>
> - if (desc && !(desc->vm_flags & VM_MAYSHARE) && h_cg) {
> + if (desc && !vma_desc_test_flags(desc, VMA_MAYSHARE_BIT) && h_cg) {
> /* For private mappings, the hugetlb_cgroup uncharge info hangs
> * of the resv_map.
> */
> @@ -6665,7 +6665,7 @@ long hugetlb_reserve_pages(struct inode *inode,
> * consumed reservations are stored in the map. Hence, nothing
> * else has to be done for private mappings here
> */
> - if (!desc || desc->vm_flags & VM_MAYSHARE) {
> + if (!desc || vma_desc_test_flags(desc, VMA_MAYSHARE_BIT)) {
> add = region_add(resv_map, from, to, regions_needed, h, h_cg);
>
> if (unlikely(add < 0)) {
> @@ -6729,7 +6729,7 @@ long hugetlb_reserve_pages(struct inode *inode,
> hugetlb_cgroup_uncharge_cgroup_rsvd(hstate_index(h),
> chg * pages_per_huge_page(h), h_cg);
> out_err:
> - if (!desc || desc->vm_flags & VM_MAYSHARE)
> + if (!desc || vma_desc_test_flags(desc, VMA_MAYSHARE_BIT))
> /* Only call region_abort if the region_chg succeeded but the
> * region_add failed or didn't run.
> */
> diff --git a/mm/memfd.c b/mm/memfd.c
> index ab5312aff14b..5f95f639550c 100644
> --- a/mm/memfd.c
> +++ b/mm/memfd.c
> @@ -87,7 +87,7 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
> gfp_mask &= ~(__GFP_HIGHMEM | __GFP_MOVABLE);
> idx >>= huge_page_order(h);
>
> - nr_resv = hugetlb_reserve_pages(inode, idx, idx + 1, NULL, 0);
> + nr_resv = hugetlb_reserve_pages(inode, idx, idx + 1, NULL, EMPTY_VMA_FLAGS);
> if (nr_resv < 0)
> return ERR_PTR(nr_resv);
>
> @@ -464,7 +464,7 @@ static struct file *alloc_file(const char *name, unsigned int flags)
> int err = 0;
>
> if (flags & MFD_HUGETLB) {
> - file = hugetlb_file_setup(name, 0, VM_NORESERVE,
> + file = hugetlb_file_setup(name, 0, mk_vma_flags(VMA_NORESERVE_BIT),
> HUGETLB_ANONHUGE_INODE,
> (flags >> MFD_HUGE_SHIFT) &
> MFD_HUGE_MASK);
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 8771b276d63d..038ff5f09df0 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -594,7 +594,7 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
> * taken when vm_ops->mmap() is called
> */
> file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
> - VM_NORESERVE,
> + mk_vma_flags(VMA_NORESERVE_BIT),
> HUGETLB_ANONHUGE_INODE,
> (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
> if (IS_ERR(file))
> --
> 2.52.0
>