linux-kernel - Re: [PATCH v2 4/4] mm, madvise: use standard madvise locking in madvise_set_anon

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Message-ID: <ff42d50e-ff56-4498-9d4b-33c04dbeebed@suse.cz>
Date: Tue, 24 Jun 2025 19:03:13 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Andrew Morton <akpm@...ux-foundation.org>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 David Hildenbrand <david@...hat.com>, Jann Horn <jannh@...gle.com>,
 Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Colin Cross <ccross@...gle.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] mm, madvise: use standard madvise locking in
 madvise_set_anon_name()

On 6/24/25 15:03, Vlastimil Babka wrote:
> Use madvise_lock()/madvise_unlock() in madvise_set_anon_name() in the
> same way as in do_madvise(). This narrows the lock scope a bit and
> reuses existing functionality. get_lock_mode() already picks the correct
> MADVISE_MMAP_WRITE_LOCK mode for __MADV_SET_ANON_VMA_NAME so we can just
> remove the explicit assignment.

Additional paragraph here:

There is a user visible change in that the prctl(PR_SET_VMA,
PR_SET_VMA_ANON_NAME...) might now return -EINTR.

> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> ---
>  mm/madvise.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index cae064479cdf908707c45b941bd03d43d095eab6..ee02ccd0315a146cdb3001cd189e03be9e48a2ea 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -2082,10 +2082,10 @@ static int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
>  {
>  	unsigned long end;
>  	unsigned long len;
> +	int error;
>  	struct madvise_behavior madv_behavior = {
>  		.mm = mm,
>  		.behavior = __MADV_SET_ANON_VMA_NAME,
> -		.lock_mode = MADVISE_MMAP_WRITE_LOCK,
>  		.anon_name = anon_name,
>  	};
>  
> @@ -2106,7 +2106,14 @@ static int madvise_set_anon_name(struct mm_struct *mm, unsigned long start,
>  
>  	madv_behavior.range.start = start;
>  	madv_behavior.range.end = end;
> -	return madvise_walk_vmas(&madv_behavior);
> +
> +	error = madvise_lock(&madv_behavior);
> +	if (error)
> +		return error;
> +	error = madvise_walk_vmas(&madv_behavior);
> +	madvise_unlock(&madv_behavior);
> +
> +	return error;
>  }
>  
>  int set_anon_vma_name(unsigned long addr, unsigned long size,
> @@ -2136,9 +2143,7 @@ int set_anon_vma_name(unsigned long addr, unsigned long size,
>  			return -ENOMEM;
>  	}
>  
> -	mmap_write_lock(mm);
>  	error = madvise_set_anon_name(mm, addr, size, anon_name);
> -	mmap_write_unlock(mm);
>  	anon_vma_name_put(anon_name);
>  
>  	return error;
>