On 07/02/2020 07:37 PM, Catalin Marinas wrote:
> On Thu, Jun 18, 2020 at 06:45:29AM +0530, Anshuman Khandual wrote:
>> There are many instances where vmemap allocation is often switched between
>> regular memory and device memory just based on whether altmap is available
>> or not. vmemmap_alloc_block_buf() is used in various platforms to allocate
>> vmemmap mappings. Lets also enable it to handle altmap based device memory
>> allocation along with existing regular memory allocations. This will help
>> in avoiding the altmap based allocation switch in many places.
>>
>> While here also implement a regular memory allocation fallback mechanism
>> when the first preferred device memory allocation fails. This will ensure
>> preserving the existing semantics on powerpc platform. To summarize there
>> are three different methods to call vmemmap_alloc_block_buf().
>>
>> (., NULL, false) /* Allocate from system RAM */
>> (., altmap, false) /* Allocate from altmap without any fallback */
>> (., altmap, true) /* Allocate from altmap with fallback (system RAM) */
> [...]
>> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
>> index bc73abf0bc25..01e25b56eccb 100644
>> --- a/arch/powerpc/mm/init_64.c
>> +++ b/arch/powerpc/mm/init_64.c
>> @@ -225,12 +225,12 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
>> * fall back to system memory if the altmap allocation fail.
>> */
>> if (altmap && !altmap_cross_boundary(altmap, start, page_size)) {
>> - p = altmap_alloc_block_buf(page_size, altmap);
>> - if (!p)
>> - pr_debug("altmap block allocation failed, falling back to system memory");
>> + p = vmemmap_alloc_block_buf(page_size, node,
>> + altmap, true);
>> + } else {
>> + p = vmemmap_alloc_block_buf(page_size, node,
>> + NULL, false);
>> }
>> - if (!p)
>> - p = vmemmap_alloc_block_buf(page_size, node);
>> if (!p)
>> return -ENOMEM;
>
> Is the fallback argument actually necessary. It may be cleaner to just
> leave the code as is with the choice between altmap and NULL. If an arch
> needs a fallback (only powerpc), they have the fallback in place
> already. I don't see the powerpc code any better after this change.
>
> I'm fine with the altmap argument though.
Okay. Will drop 'fallback' from vmemmap_alloc_block_buf() and update the
callers. There will also be a single change in the subsequent patch i.e
vmemmap_alloc_block_buf(PMD_SIZE, node, altmap).
