> On Jul 10, 2025, at 5:19 PM, Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> 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 <Liam.Howlett@xxxxxxxxxx> wrote: >>> >>> * Vitaly Wool <vitaly.wool@xxxxxxxxxxx <mailto:vitaly.wool@xxxxxxxxxxx>> [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 <vitaly.wool@xxxxxxxxxxx> >>>> Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> >>>> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> >>>> --- >>>> 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
