Re: [PATCH 1/4] mm/madvise: split out mmap locking operations for madvise()

[Liam R. Howlett]

* SeongJae Park <sj@xxxxxxxxxx> [250206 01:15]:
> Split out the madvise behavior-dependent mmap_lock operations from
> do_madvise(), for easier reuse of the logic in an upcoming change.
> 
> Reviewed-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>

Reviewed-by: Liam R. Howlett <howlett@xxxxxxxxx>

> ---
>  mm/madvise.c | 45 ++++++++++++++++++++++++++++++++-------------
>  1 file changed, 32 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index c8e28d51978a..df5a87a1846a 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1567,6 +1567,33 @@ int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
>  				 madvise_vma_anon_name);
>  }
>  #endif /* CONFIG_ANON_VMA_NAME */
> +
> +static int madvise_lock(struct mm_struct *mm, int behavior)
> +{
> +
> +#ifdef CONFIG_MEMORY_FAILURE
> +	if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
> +		return 0;
> +#endif
> +
> +	if (madvise_need_mmap_write(behavior)) {
> +		if (mmap_write_lock_killable(mm))
> +			return -EINTR;
> +	} else {
> +		mmap_read_lock(mm);
> +	}
> +	return 0;
> +
> +}
> +
> +static void madvise_unlock(struct mm_struct *mm, int behavior)
> +{
> +	if (madvise_need_mmap_write(behavior))
> +		mmap_write_unlock(mm);
> +	else
> +		mmap_read_unlock(mm);
> +}
> +
>  /*
>   * The madvise(2) system call.
>   *
> @@ -1643,7 +1670,6 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh
>  {
>  	unsigned long end;
>  	int error;
> -	int write;
>  	size_t len;
>  	struct blk_plug plug;
>  
> @@ -1665,19 +1691,15 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh
>  	if (end == start)
>  		return 0;
>  
> +	error = madvise_lock(mm, behavior);
> +	if (error)
> +		return error;
> +
>  #ifdef CONFIG_MEMORY_FAILURE
>  	if (behavior == MADV_HWPOISON || behavior == MADV_SOFT_OFFLINE)
>  		return madvise_inject_error(behavior, start, start + len_in);
>  #endif
>  
> -	write = madvise_need_mmap_write(behavior);
> -	if (write) {
> -		if (mmap_write_lock_killable(mm))
> -			return -EINTR;
> -	} else {
> -		mmap_read_lock(mm);
> -	}
> -
>  	start = untagged_addr_remote(mm, start);
>  	end = start + len;
>  
> @@ -1694,10 +1716,7 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh
>  	}
>  	blk_finish_plug(&plug);
>  
> -	if (write)
> -		mmap_write_unlock(mm);
> -	else
> -		mmap_read_unlock(mm);
> +	madvise_unlock(mm, behavior);
>  
>  	return error;
>  }
> -- 
> 2.39.5