[v2] madvise anon_name cleanups

[PATCH v2 4/4] mm, madvise: use standard madvise locking in madvise_set_anon_name()

Posted by Vlastimil Babka 3 months, 2 weeks ago

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.

Signed-off-by: Vlastimil Babka <vbabka@suse.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;

-- 
2.50.0

Re: [PATCH v2 4/4] mm, madvise: use standard madvise locking in madvise_set_anon_name()

Posted by Vlastimil Babka 3 months, 2 weeks ago

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@suse.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;
>

Re: [PATCH v2 4/4] mm, madvise: use standard madvise locking in madvise_set_anon_name()

Posted by Lorenzo Stoakes 3 months, 2 weeks ago

On Tue, Jun 24, 2025 at 03:03:48PM +0200, 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.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

This is a nice idea, hadn't thought of it :) aren't we making anon vma name
behave now :P

I mean this is a _minor_ difference in functionality in that we will now
use mmap_write_lock_killable() and could fail to lock on fatal signal
whereas before we unconditionally lock but I think that's fine, and
possibly even... desirable actually?

At any rate this is all nice, thanks again!

> ---
>  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;
>
> --
> 2.50.0
>

Re: [PATCH v2 4/4] mm, madvise: use standard madvise locking in madvise_set_anon_name()

Posted by Vlastimil Babka 3 months, 2 weeks ago

On 6/24/25 17:45, Lorenzo Stoakes wrote:
> On Tue, Jun 24, 2025 at 03:03:48PM +0200, 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.
>>
>> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> 
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> 
> This is a nice idea, hadn't thought of it :) aren't we making anon vma name
> behave now :P
> 
> I mean this is a _minor_ difference in functionality in that we will now
> use mmap_write_lock_killable() and could fail to lock on fatal signal
> whereas before we unconditionally lock but I think that's fine, and
> possibly even... desirable actually?

Right! I'll add a note to the changelog. It's changing existing uapi but
hopefully not in a way that userspace would become broken. I mean even the
other madvise modes only got killable locks later tat some point after
introduction, no?

> 
> At any rate this is all nice, thanks again!
> 
>> ---
>>  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;
>>
>> --
>> 2.50.0
>>

Re: [PATCH v2 4/4] mm, madvise: use standard madvise locking in madvise_set_anon_name()

Posted by David Hildenbrand 3 months, 2 weeks ago

On 24.06.25 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.
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

Re: [PATCH v2 4/4] mm, madvise: use standard madvise locking in madvise_set_anon_name()

Posted by Suren Baghdasaryan 3 months, 2 weeks ago

On Tue, Jun 24, 2025 at 7:06 AM David Hildenbrand <david@redhat.com> wrote:
>
> On 24.06.25 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.
> >
> > Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> > ---
>
> Acked-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Suren Baghdasaryan <surenb@google.com>

>
> --
> Cheers,
>
> David / dhildenb
>