Re: [PATCH v2 09/13] mm: update all remaining mmap_prepare users to use vma_flags_t

On Thu, Jan 22, 2026 at 04:06:18PM +0000, Lorenzo Stoakes wrote:
> We will be shortly removing the vm_flags_t field from vm_area_desc so we
> need to update all mmap_prepare users to only use the dessc->vma_flags
> field.
> 
> This patch achieves that and makes all ancillary changes required to make
> this possible.
> 
> This lays the groundwork for future work to eliminate the use of vm_flags_t
> in vm_area_desc altogether and more broadly throughout the kernel.
> 
> While we're here, we take the opportunity to replace VM_REMAP_FLAGS with
> VMA_REMAP_FLAGS, the vma_flags_t equivalent.
> 
> No functional changes intended.
> 
> Signed-off-by: Lorenzo Stoakes <[email protected]>
> ---
>  drivers/char/mem.c       |  6 +++---
>  drivers/dax/device.c     | 10 +++++-----
>  fs/aio.c                 |  2 +-
>  fs/erofs/data.c          |  5 +++--
>  fs/ext4/file.c           |  4 ++--
>  fs/ntfs3/file.c          |  2 +-
>  fs/orangefs/file.c       |  4 ++--
>  fs/ramfs/file-nommu.c    |  2 +-
>  fs/resctrl/pseudo_lock.c |  2 +-
>  fs/romfs/mmap-nommu.c    |  2 +-
>  fs/xfs/xfs_file.c        |  4 ++--
>  fs/zonefs/file.c         |  3 ++-
>  include/linux/dax.h      |  8 ++++----
>  include/linux/mm.h       | 24 +++++++++++++++++++-----
>  kernel/relay.c           |  2 +-
>  mm/memory.c              | 17 ++++++++---------
>  16 files changed, 56 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index 52039fae1594..cca4529431f8 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -306,7 +306,7 @@ static unsigned zero_mmap_capabilities(struct file *file)
>  /* can't do an in-place private mapping if there's no MMU */
>  static inline int private_mapping_ok(struct vm_area_desc *desc)
>  {
> -	return is_nommu_shared_mapping(desc->vm_flags);
> +	return is_nommu_shared_vma_flags(&desc->vma_flags);
>  }
>  #else
>  
> @@ -360,7 +360,7 @@ static int mmap_mem_prepare(struct vm_area_desc *desc)
>  
>  	desc->vm_ops = &mmap_mem_ops;
>  
> -	/* Remap-pfn-range will mark the range VM_IO. */
> +	/* Remap-pfn-range will mark the range with the I/O flag. */
>  	mmap_action_remap_full(desc, desc->pgoff);
>  	/* We filter remap errors to -EAGAIN. */
>  	desc->action.error_hook = mmap_filter_error;
> @@ -520,7 +520,7 @@ static int mmap_zero_prepare(struct vm_area_desc *desc)
>  #ifndef CONFIG_MMU
>  	return -ENOSYS;
>  #endif
> -	if (desc->vm_flags & VM_SHARED)
> +	if (vma_desc_test_flags(desc, VMA_SHARED_BIT))
>  		return shmem_zero_setup_desc(desc);
>  
>  	desc->action.success_hook = mmap_zero_private_success;
> diff --git a/drivers/dax/device.c b/drivers/dax/device.c
> index 22999a402e02..528e81240c4d 100644
> --- a/drivers/dax/device.c
> +++ b/drivers/dax/device.c
> @@ -13,7 +13,7 @@
>  #include "dax-private.h"
>  #include "bus.h"
>  
> -static int __check_vma(struct dev_dax *dev_dax, vm_flags_t vm_flags,
> +static int __check_vma(struct dev_dax *dev_dax, vma_flags_t flags,
>  		       unsigned long start, unsigned long end, struct file *file,
>  		       const char *func)
>  {
> @@ -24,7 +24,7 @@ static int __check_vma(struct dev_dax *dev_dax, vm_flags_t vm_flags,
>  		return -ENXIO;
>  
>  	/* prevent private mappings from being established */
> -	if ((vm_flags & VM_MAYSHARE) != VM_MAYSHARE) {
> +	if (!vma_flags_test(&flags, VMA_MAYSHARE_BIT)) {
>  		dev_info_ratelimited(dev,
>  				"%s: %s: fail, attempted private mapping\n",
>  				current->comm, func);
> @@ -53,7 +53,7 @@ static int __check_vma(struct dev_dax *dev_dax, vm_flags_t vm_flags,
>  static int check_vma(struct dev_dax *dev_dax, struct vm_area_struct *vma,
>  		     const char *func)
>  {
> -	return __check_vma(dev_dax, vma->vm_flags, vma->vm_start, vma->vm_end,
> +	return __check_vma(dev_dax, vma->flags, vma->vm_start, vma->vm_end,
>  			   vma->vm_file, func);
>  }
>  
> @@ -306,14 +306,14 @@ static int dax_mmap_prepare(struct vm_area_desc *desc)
>  	 * fault time.
>  	 */
>  	id = dax_read_lock();
> -	rc = __check_vma(dev_dax, desc->vm_flags, desc->start, desc->end, filp,
> +	rc = __check_vma(dev_dax, desc->vma_flags, desc->start, desc->end, filp,
>  			 __func__);
>  	dax_read_unlock(id);
>  	if (rc)
>  		return rc;
>  
>  	desc->vm_ops = &dax_vm_ops;
> -	desc->vm_flags |= VM_HUGEPAGE;
> +	vma_desc_set_flags(desc, VMA_HUGEPAGE_BIT);
>  	return 0;
>  }
>  
> diff --git a/fs/aio.c b/fs/aio.c
> index 0a23a8c0717f..59b67b8da1b2 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -394,7 +394,7 @@ static const struct vm_operations_struct aio_ring_vm_ops = {
>  
>  static int aio_ring_mmap_prepare(struct vm_area_desc *desc)
>  {
> -	desc->vm_flags |= VM_DONTEXPAND;
> +	vma_desc_set_flags(desc, VMA_DONTEXPAND_BIT);
>  	desc->vm_ops = &aio_ring_vm_ops;
>  	return 0;
>  }
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index bb13c4cb8455..e7bc29e764c6 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -438,11 +438,12 @@ static int erofs_file_mmap_prepare(struct vm_area_desc *desc)
>  	if (!IS_DAX(file_inode(desc->file)))
>  		return generic_file_readonly_mmap_prepare(desc);
>  
> -	if ((desc->vm_flags & VM_SHARED) && (desc->vm_flags & VM_MAYWRITE))
> +	if (vma_desc_test_flags(desc, VMA_SHARED_BIT) &&
> +	    vma_desc_test_flags(desc, VMA_MAYWRITE_BIT))
>  		return -EINVAL;
>  
>  	desc->vm_ops = &erofs_dax_vm_ops;
> -	desc->vm_flags |= VM_HUGEPAGE;
> +	vma_desc_set_flags(desc, VMA_HUGEPAGE_BIT);
>  	return 0;
>  }
>  #else
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 7a8b30932189..dfd5f4fe1647 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -822,13 +822,13 @@ static int ext4_file_mmap_prepare(struct vm_area_desc *desc)
>  	 * We don't support synchronous mappings for non-DAX files and
>  	 * for DAX files if underneath dax_device is not synchronous.
>  	 */
> -	if (!daxdev_mapping_supported(desc->vm_flags, file_inode(file), dax_dev))
> +	if (!daxdev_mapping_supported(desc, file_inode(file), dax_dev))
>  		return -EOPNOTSUPP;
>  
>  	file_accessed(file);
>  	if (IS_DAX(file_inode(file))) {
>  		desc->vm_ops = &ext4_dax_vm_ops;
> -		desc->vm_flags |= VM_HUGEPAGE;
> +		vma_desc_set_flags(desc, VMA_HUGEPAGE_BIT);
>  	} else {
>  		desc->vm_ops = &ext4_file_vm_ops;
>  	}
> diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
> index 2e7b2e566ebe..2902fc6d9a85 100644
> --- a/fs/ntfs3/file.c
> +++ b/fs/ntfs3/file.c
> @@ -347,7 +347,7 @@ static int ntfs_file_mmap_prepare(struct vm_area_desc *desc)
>  	struct inode *inode = file_inode(file);
>  	struct ntfs_inode *ni = ntfs_i(inode);
>  	u64 from = ((u64)desc->pgoff << PAGE_SHIFT);
> -	bool rw = desc->vm_flags & VM_WRITE;
> +	const bool rw = vma_desc_test_flags(desc, VMA_WRITE_BIT);
>  	int err;
>  
>  	/* Avoid any operation if inode is bad. */
> diff --git a/fs/orangefs/file.c b/fs/orangefs/file.c
> index 919f99b16834..c75aa3f419b1 100644
> --- a/fs/orangefs/file.c
> +++ b/fs/orangefs/file.c
> @@ -411,8 +411,8 @@ static int orangefs_file_mmap_prepare(struct vm_area_desc *desc)
>  		     "orangefs_file_mmap: called on %pD\n", file);
>  
>  	/* set the sequential readahead hint */
> -	desc->vm_flags |= VM_SEQ_READ;
> -	desc->vm_flags &= ~VM_RAND_READ;
> +	vma_desc_set_flags(desc, VMA_SEQ_READ_BIT);
> +	vma_desc_clear_flags(desc, VMA_RAND_READ_BIT);
>  
>  	file_accessed(file);
>  	desc->vm_ops = &orangefs_file_vm_ops;
> diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
> index 77b8ca2757e0..0f8e838ece07 100644
> --- a/fs/ramfs/file-nommu.c
> +++ b/fs/ramfs/file-nommu.c
> @@ -264,7 +264,7 @@ static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
>   */
>  static int ramfs_nommu_mmap_prepare(struct vm_area_desc *desc)
>  {
> -	if (!is_nommu_shared_mapping(desc->vm_flags))
> +	if (!is_nommu_shared_vma_flags(&desc->vma_flags))
>  		return -ENOSYS;
>  
>  	file_accessed(desc->file);
> diff --git a/fs/resctrl/pseudo_lock.c b/fs/resctrl/pseudo_lock.c
> index 0bfc13c5b96d..e81d71abfe54 100644
> --- a/fs/resctrl/pseudo_lock.c
> +++ b/fs/resctrl/pseudo_lock.c
> @@ -1044,7 +1044,7 @@ static int pseudo_lock_dev_mmap_prepare(struct vm_area_desc *desc)
>  	 * Ensure changes are carried directly to the memory being mapped,
>  	 * do not allow copy-on-write mapping.
>  	 */
> -	if (!(desc->vm_flags & VM_SHARED)) {
> +	if (!vma_desc_test_flags(desc, VMA_SHARED_BIT)) {
>  		mutex_unlock(&rdtgroup_mutex);
>  		return -EINVAL;
>  	}
> diff --git a/fs/romfs/mmap-nommu.c b/fs/romfs/mmap-nommu.c
> index 4b77c6dc4418..7c3a1a7fecee 100644
> --- a/fs/romfs/mmap-nommu.c
> +++ b/fs/romfs/mmap-nommu.c
> @@ -63,7 +63,7 @@ static unsigned long romfs_get_unmapped_area(struct file *file,
>   */
>  static int romfs_mmap_prepare(struct vm_area_desc *desc)
>  {
> -	return is_nommu_shared_mapping(desc->vm_flags) ? 0 : -ENOSYS;
> +	return is_nommu_shared_vma_flags(&desc->vma_flags) ? 0 : -ENOSYS;
>  }
>  
>  static unsigned romfs_mmap_capabilities(struct file *file)
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 7874cf745af3..1238ec018bc7 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1974,14 +1974,14 @@ xfs_file_mmap_prepare(
>  	 * We don't support synchronous mappings for non-DAX files and
>  	 * for DAX files if underneath dax_device is not synchronous.
>  	 */
> -	if (!daxdev_mapping_supported(desc->vm_flags, file_inode(file),
> +	if (!daxdev_mapping_supported(desc, file_inode(file),
>  				      target->bt_daxdev))
>  		return -EOPNOTSUPP;
>  
>  	file_accessed(file);
>  	desc->vm_ops = &xfs_file_vm_ops;
>  	if (IS_DAX(inode))
> -		desc->vm_flags |= VM_HUGEPAGE;
> +		vma_desc_set_flags(desc, VMA_HUGEPAGE_BIT);
>  	return 0;
>  }
>  
> diff --git a/fs/zonefs/file.c b/fs/zonefs/file.c
> index c1e5e30e90a0..8a7161fc49e5 100644
> --- a/fs/zonefs/file.c
> +++ b/fs/zonefs/file.c
> @@ -333,7 +333,8 @@ static int zonefs_file_mmap_prepare(struct vm_area_desc *desc)
>  	 * ordering between msync() and page cache writeback.
>  	 */
>  	if (zonefs_inode_is_seq(file_inode(file)) &&
> -	    (desc->vm_flags & VM_SHARED) && (desc->vm_flags & VM_MAYWRITE))
> +	    vma_desc_test_flags(desc, VMA_SHARED_BIT) &&
> +	    vma_desc_test_flags(desc, VMA_MAYWRITE_BIT))
>  		return -EINVAL;
>  
>  	file_accessed(file);
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index 9d624f4d9df6..bf103f317cac 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -65,11 +65,11 @@ size_t dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
>  /*
>   * Check if given mapping is supported by the file / underlying device.
>   */
> -static inline bool daxdev_mapping_supported(vm_flags_t vm_flags,
> +static inline bool daxdev_mapping_supported(const struct vm_area_desc *desc,
>  					    const struct inode *inode,
>  					    struct dax_device *dax_dev)
>  {
> -	if (!(vm_flags & VM_SYNC))
> +	if (!vma_desc_test_flags(desc, VMA_SYNC_BIT))
>  		return true;
>  	if (!IS_DAX(inode))
>  		return false;
> @@ -111,11 +111,11 @@ static inline void set_dax_nomc(struct dax_device *dax_dev)
>  static inline void set_dax_synchronous(struct dax_device *dax_dev)
>  {
>  }
> -static inline bool daxdev_mapping_supported(vm_flags_t vm_flags,
> +static inline bool daxdev_mapping_supported(const struct vm_area_desc *desc,
>  					    const struct inode *inode,
>  					    struct dax_device *dax_dev)
>  {
> -	return !(vm_flags & VM_SYNC);
> +	return !vma_desc_test_flags(desc, VMA_SYNC_BIT);
>  }
>  static inline size_t dax_recovery_write(struct dax_device *dax_dev,
>  		pgoff_t pgoff, void *addr, size_t bytes, struct iov_iter *i)
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index fd93317193e0..e31f72a021ef 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -550,17 +550,18 @@ enum {
>  /*
>   * Physically remapped pages are special. Tell the
>   * rest of the world about it:
> - *   VM_IO tells people not to look at these pages
> + *   IO tells people not to look at these pages
>   *	(accesses can have side effects).
> - *   VM_PFNMAP tells the core MM that the base pages are just
> + *   PFNMAP tells the core MM that the base pages are just
>   *	raw PFN mappings, and do not have a "struct page" associated
>   *	with them.
> - *   VM_DONTEXPAND
> + *   DONTEXPAND
>   *      Disable vma merging and expanding with mremap().
> - *   VM_DONTDUMP
> + *   DONTDUMP
>   *      Omit vma from core dump, even when VM_IO turned off.
>   */

I don't think it's useful to erase the VM_ prefix off the flags. These still
exist, so maybe the alternative would be to rename them to e.g VMA_IO in
comments, etc. I think just saying "IO" or "the I/O flag" above is ambiguous.

> -#define VM_REMAP_FLAGS (VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)
> +#define VMA_REMAP_FLAGS mk_vma_flags(VMA_IO_BIT, VMA_PFNMAP_BIT,	\
> +				     VMA_DONTEXPAND_BIT, VMA_DONTDUMP_BIT)

as a sidenote, these flags are no longer constant expressions and thus

static vma_flags_t flags = VMA_REMAP_FLAGS;

can't compile.

Rest LGTM though.

Acked-by: Pedro Falcato <[email protected]>

-- 
Pedro