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

Lorenzo Stoakes
2026-01-22T16:07:58Z

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>
---
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