> On Jul 10, 2025, at 5:19 PM, Lorenzo Stoakes <[email protected]>
> wrote:
>
> On Thu, Jul 10, 2025 at 08:21:19AM +0200, Vitaly Wool wrote:
>>
>>
>>> On Jul 9, 2025, at 9:01 PM, Liam R. Howlett <[email protected]> wrote:
>>>
>>> * Vitaly Wool <[email protected] <mailto:[email protected]>>
>>> [250709 13:24]:
>>>> Reimplement vrealloc() to be able to set node and alignment should
>>>> a user need to do so. Rename the function to vrealloc_node_align()
>>>> to better match what it actually does now and introduce macros for
>>>> vrealloc() and friends for backward compatibility.
>>>>
>>>> With that change we also provide the ability for the Rust part of
>>>> the kernel to set node and alignment in its allocations.
>>>>
>>>> Signed-off-by: Vitaly Wool <[email protected]>
>>>> Reviewed-by: Uladzislau Rezki (Sony) <[email protected]>
>>>> Reviewed-by: Vlastimil Babka <[email protected]>
>>>> ---
>>>> include/linux/vmalloc.h | 12 +++++++++---
>>>> mm/nommu.c | 3 ++-
>>>> mm/vmalloc.c | 31 ++++++++++++++++++++++++++-----
>>>> 3 files changed, 37 insertions(+), 9 deletions(-)
>>>>
>>> ...
>>>
>>>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>>>> index 6dbcdceecae1..03dd06097b25 100644
>>>> --- a/mm/vmalloc.c
>>>> +++ b/mm/vmalloc.c
>>>> @@ -4089,19 +4089,31 @@ void *vzalloc_node_noprof(unsigned long size, int
>>>> node)
>>>> EXPORT_SYMBOL(vzalloc_node_noprof);
>>>>
>>>> /**
>>>> - * vrealloc - reallocate virtually contiguous memory; contents remain
>>>> unchanged
>>>> + * vrealloc_node_align_noprof - reallocate virtually contiguous memory;
>>>> contents
>>>> + * remain unchanged
>>>> * @p: object to reallocate memory for
>>>> * @size: the size to reallocate
>>>> + * @align: requested alignment
>>>> * @flags: the flags for the page level allocator
>>>> + * @nid: node number of the target node
>>>> + *
>>>> + * If @p is %NULL, vrealloc_XXX() behaves exactly like vmalloc(). If
>>>> @size is
>>>> + * 0 and @p is not a %NULL pointer, the object pointed to is freed.
>>>> *
>>>> - * If @p is %NULL, vrealloc() behaves exactly like vmalloc(). If @size is
>>>> 0 and
>>>> - * @p is not a %NULL pointer, the object pointed to is freed.
>>>> + * if @nid is not NUMA_NO_NODE, this function will try to allocate memory
>>>> on
>>>> + * the given node. If reallocation is not necessary (e. g. the new size
>>>> is less
>>>> + * than the current allocated size), the current allocation will be
>>>> preserved
>>>> + * unless __GFP_THISNODE is set. In the latter case a new allocation on
>>>> the
>>>> + * requested node will be attempted.
>
> Agreed with Liam, this is completely unreadable.
>
> I think the numa node stuff is unnecesasry, that's pretty much inferred.
>
> I'd just go with something like 'if the function can void having to reallocate
> then it does'.
>
> Nice and simple :)
I think it is important to stress that the function is not always following the
specified nid.
How about “If the caller wants the new memory to be on specific node *only*,
__GFP_THISNODE flag should be set, otherwise the function will try to avoid
reallocation and possibly disregard the specified @nid” ?
>
>>>
>>> I am having a very hard time understanding what you mean here. What is
>>> the latter case?
>>>
>>> If @nis is !NUMA_NO_NODE, the allocation will be attempted on the given
>>> node. Then things sort of get confusing. What is the latter case?
>>
>> The latter case is __GFP_THISNODE present in flags. That’s the latest
>> if-clause in this paragraph.
>>>
>>>> *
>>>> * If __GFP_ZERO logic is requested, callers must ensure that, starting
>>>> with the
>>>> * initial memory allocation, every subsequent call to this API for the same
>>>> * memory allocation is flagged with __GFP_ZERO. Otherwise, it is possible
>>>> that
>>>> * __GFP_ZERO is not fully honored by this API.
>>>> *
>>>> + * If the requested alignment is bigger than the one the *existing*
>>>> allocation
>>>> + * has, this function will fail.
>>>> + *
>>>
>>> It might be better to say something like:
>>> Requesting an alignment that is bigger than the alignment of the
>>> *existing* allocation will fail.
>>>
>>
>> The whole function description in fact consists of several if-clauses (some
>> of which are nested) so I am just following the pattern here.
>
> Right, but in no sane world is essentially describing a series of if-clauses
> in
> a kerneldoc a thing.
>
> Just it keep it simple, this is meant to be an overview, people can go read
> the
> code if they need details :)
>
Alright, no strong feelings about it anyway. Will reword as you guys suggest.
Thanks,
Vitaly
