Re: [RFC PATCH v3 09/10] mm: create __do_mmap() to take an mm_struct * arg

[Kirill A. Shutemov]

On Tue, Sep 03, 2024 at 04:22:40PM -0700, Anthony Yznaga wrote:
> In preparation for mapping objects into an mshare region, create
> __do_mmap() to allow mapping into a specified mm. There are no
> functional changes otherwise.
> 
> Signed-off-by: Anthony Yznaga <anthony.yznaga@xxxxxxxxxx>
> ---
>  include/linux/mm.h | 18 +++++++++++++++++-
>  mm/mmap.c          | 12 +++++-------
>  2 files changed, 22 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 3aa0b3322284..a9afbda73cb0 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3409,11 +3409,27 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
>  
>  extern unsigned long mmap_region(struct file *file, unsigned long addr,
>  	unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
> -	struct list_head *uf);
> +	struct list_head *uf, struct mm_struct *mm);
> +#ifdef CONFIG_MMU
> +extern unsigned long __do_mmap(struct file *file, unsigned long addr,
> +	unsigned long len, unsigned long prot, unsigned long flags,
> +	vm_flags_t vm_flags, unsigned long pgoff, unsigned long *populate,
> +	struct list_head *uf, struct mm_struct *mm);
> +static inline unsigned long do_mmap(struct file *file, unsigned long addr,
> +	unsigned long len, unsigned long prot, unsigned long flags,
> +	vm_flags_t vm_flags, unsigned long pgoff, unsigned long *populate,
> +	struct list_head *uf)
> +{
> +	return __do_mmap(file, addr, len, prot, flags, vm_flags, pgoff,
> +			 populate, uf, current->mm);
> +}
> +#else
>  extern unsigned long do_mmap(struct file *file, unsigned long addr,
>  	unsigned long len, unsigned long prot, unsigned long flags,
>  	vm_flags_t vm_flags, unsigned long pgoff, unsigned long *populate,
>  	struct list_head *uf);
> +#endif
> +
>  extern int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm,
>  			 unsigned long start, size_t len, struct list_head *uf,
>  			 bool unlock);
> diff --git a/mm/mmap.c b/mm/mmap.c
> index d0dfc85b209b..4112f18e7302 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1250,15 +1250,14 @@ static inline bool file_mmap_ok(struct file *file, struct inode *inode,
>  }
>  
>  /*
> - * The caller must write-lock current->mm->mmap_lock.
> + * The caller must write-lock mm->mmap_lock.
>   */
> -unsigned long do_mmap(struct file *file, unsigned long addr,
> +unsigned long __do_mmap(struct file *file, unsigned long addr,
>  			unsigned long len, unsigned long prot,
>  			unsigned long flags, vm_flags_t vm_flags,
>  			unsigned long pgoff, unsigned long *populate,
> -			struct list_head *uf)
> +			struct list_head *uf, struct mm_struct *mm)

Argument list getting too long. At some point we need to have a struct to
pass them around.

>  {
> -	struct mm_struct *mm = current->mm;
>  	int pkey = 0;
>  
>  	*populate = 0;
> @@ -1465,7 +1464,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
>  			vm_flags |= VM_NORESERVE;
>  	}
>  
> -	addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
> +	addr = mmap_region(file, addr, len, vm_flags, pgoff, uf, mm);
>  	if (!IS_ERR_VALUE(addr) &&
>  	    ((vm_flags & VM_LOCKED) ||
>  	     (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
> @@ -2848,9 +2847,8 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
>  
>  unsigned long mmap_region(struct file *file, unsigned long addr,
>  		unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
> -		struct list_head *uf)
> +		struct list_head *uf, struct mm_struct *mm)
>  {
> -	struct mm_struct *mm = current->mm;
>  	struct vm_area_struct *vma = NULL;
>  	struct vm_area_struct *next, *prev, *merge;
>  	pgoff_t pglen = len >> PAGE_SHIFT;
> -- 
> 2.43.5
> 

-- 
  Kiryl Shutsemau / Kirill A. Shutemov