Re: [PATCH 07/10] mm/filemap: introduce generic_file_*_mmap_prepare() helpers

Jan Kara
2025-06-17T10:22:53Z

On Mon 16-06-25 20:33:26, Lorenzo Stoakes wrote:
> Since commit c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file
> callback"), the f_op->mmap() hook has been deprecated in favour of
> f_op->mmap_prepare().
>
> The generic mmap handlers are very simple, so we can very easily convert
> these in advance of converting file systems which use them.
>
> This patch does so.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> include/linux/fs.h | 6 ++++--
> mm/filemap.c | 29 +++++++++++++++++++++++++++++
> 2 files changed, 33 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 7120f80255b3..65cffc445fcc 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3395,8 +3395,10 @@ extern void inode_add_lru(struct inode *inode);
> extern int sb_set_blocksize(struct super_block *, int);
> extern int sb_min_blocksize(struct super_block *, int);
>
> -extern int generic_file_mmap(struct file *, struct vm_area_struct *);
> -extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
> +int generic_file_mmap(struct file *, struct vm_area_struct *);
> +int generic_file_mmap_prepare(struct vm_area_desc *desc);
> +int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
> +int generic_file_readonly_mmap_prepare(struct vm_area_desc *desc);
> extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *);
> int generic_write_checks_count(struct kiocb *iocb, loff_t *count);
> extern int generic_write_check_limits(struct file *file, loff_t pos,
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 93fbc2ef232a..e75608cbf420 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3847,6 +3847,18 @@ int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
> return 0;
> }
>
> +int generic_file_mmap_prepare(struct vm_area_desc *desc)
> +{
> + struct file *file = desc->file;
> + struct address_space *mapping = file->f_mapping;
> +
> + if (!mapping->a_ops->read_folio)
> + return -ENOEXEC;
> + file_accessed(file);
> + desc->vm_ops = &generic_file_vm_ops;
> + return 0;
> +}
> +
> /*
> * This is for filesystems which do not implement ->writepage.
> */
> @@ -3856,6 +3868,13 @@ int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
> return -EINVAL;
> return generic_file_mmap(file, vma);
> }
> +
> +int generic_file_readonly_mmap_prepare(struct vm_area_desc *desc)
> +{
> + if (is_shared_maywrite(desc->vm_flags))
> + return -EINVAL;
> + return generic_file_mmap_prepare(desc);
> +}
> #else
> vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
> {
> @@ -3865,15 +3884,25 @@ int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
> {
> return -ENOSYS;
> }
> +int generic_file_mmap_prepare(struct vm_area_desc *desc)
> +{
> + return -ENOSYS;
> +}
> int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
> {
> return -ENOSYS;
> }
> +int generic_file_readonly_mmap_prepare(struct vm_area_desc *desc)
> +{
> + return -ENOSYS;
> +}
> #endif /* CONFIG_MMU */
>
> EXPORT_SYMBOL(filemap_page_mkwrite);
> EXPORT_SYMBOL(generic_file_mmap);
> +EXPORT_SYMBOL(generic_file_mmap_prepare);
> EXPORT_SYMBOL(generic_file_readonly_mmap);
> +EXPORT_SYMBOL(generic_file_readonly_mmap_prepare);
>
> static struct folio *do_read_cache_folio(struct address_space *mapping,
> pgoff_t index, filler_t filler, struct file *file, gfp_t gfp)
> --
> 2.49.0
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR