Re: [PATCH v3 15/16] mm: replace __GFP_NO_CODETAG with ALLOC_NO_CODETAG

[Brendan Jackman]

On Tue Jun 30, 2026 at 1:55 AM UTC, Hao Ge wrote:
> Hi Brendan
>
>
> On 2026/6/29 21:12, Brendan Jackman wrote:
>> Now that alloc_pages has an entrypoint that allows passing alloc_flags,
>> we can take advantage of this to start removing GFP flags that are only
>> used for mm-internal stuff.
>>
>> This requires also plumbing the alloc_flags into some more of the
>> allocator code, in particular __alloc_pages[_noprof]() gets an
>> alloc_flags arg to go along with its callees, and we now need to pass
>> those flags deeper into the allocator so they can reach the alloc_tag
>> code.
>>
>> No functional change intended.
>>
>> Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
>> ---
>>   mm/alloc_tag.c       | 22 ++++++----------------
>>   mm/compaction.c      |  4 ++--
>>   mm/internal.h        |  1 -
>>   mm/page_alloc.c      | 42 ++++++++++++++++++++++++------------------
>>   mm/page_alloc.h      | 17 +++++++++++++++--
>>   mm/page_frag_cache.c |  4 ++--
>>   6 files changed, 49 insertions(+), 41 deletions(-)
>>
>> diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c
>> index d9be1cf5187d9..a32a94e759b94 100644
>> --- a/mm/alloc_tag.c
>> +++ b/mm/alloc_tag.c
>> @@ -15,6 +15,8 @@
>>   #include <linux/vmalloc.h>
>>   #include <linux/kmemleak.h>
>>   
>> +#include "internal.h"
>
>
> Should we include page_alloc.h here, as we call __alloc_pages later in 
> this file?

Yeah, there are a few build failures due to me not doing a broad enough
build. From now on I will just wait for allmodconfig instead of trying
to be clever with my build tests, sorry about this.

Also, this suggests that I have not actually re-tested the alloc_tag
code since v3 so I must repeat the test described in my cover letter (I
just manually enable the feature and check the kernel boots) for v4.

>> +
>>   #define ALLOCINFO_FILE_NAME		"allocinfo"
>>   #define MODULE_ALLOC_TAG_VMAP_SIZE	(100000UL * sizeof(struct alloc_tag))
>>   #define SECTION_START(NAME)		(CODETAG_SECTION_START_PREFIX NAME)
>> @@ -783,19 +785,6 @@ struct pfn_pool {
>>   
>>   #define PFN_POOL_SIZE			((PAGE_SIZE - offsetof(struct pfn_pool, pfns)) / \
>>   					 sizeof(unsigned long))
>> -
>> -/*
>> - * Skip early PFN recording for a page allocation.  Reuses the
>> - * %__GFP_NO_OBJ_EXT bit.  Used by __alloc_tag_add_early_pfn() to avoid
>> - * recursion when allocating pages for the early PFN tracking list
>> - * itself.
>> - *
>> - * Codetags of the pages allocated with __GFP_NO_CODETAG should be
>> - * cleared (via clear_page_tag_ref()) before freeing the pages to prevent
>> - * alloc_tag_sub_check() from triggering a warning.
>> - */
>> -#define __GFP_NO_CODETAG		__GFP_NO_OBJ_EXT
>> -
>>   static struct pfn_pool *current_pfn_pool __initdata;
>>   
>>   static void __init __alloc_tag_add_early_pfn(unsigned long pfn)
>> @@ -806,7 +795,8 @@ static void __init __alloc_tag_add_early_pfn(unsigned long pfn)
>>   	do {
>>   		pool = READ_ONCE(current_pfn_pool);
>>   		if (!pool || atomic_read(&pool->count) >= PFN_POOL_SIZE) {
>> -			struct page *new_page = alloc_page(__GFP_HIGH | __GFP_NO_CODETAG);
>> +			struct page *new_page = __alloc_pages(__GFP_HIGH, 0, numa_mem_id(),
>> +							      NULL, ALLOC_NO_CODETAG);
>>   			struct pfn_pool *new;
>>   
>>   			if (!new_page) {
>> @@ -837,7 +827,7 @@ typedef void alloc_tag_add_func(unsigned long pfn);
>>   static alloc_tag_add_func __rcu *alloc_tag_add_early_pfn_ptr __refdata =
>>   	RCU_INITIALIZER(__alloc_tag_add_early_pfn);
>>   
>> -void alloc_tag_add_early_pfn(unsigned long pfn, gfp_t gfp_flags)
>> +void alloc_tag_add_early_pfn(unsigned long pfn, unsigned int alloc_flags)
>
>
> alloc_tag_add_early_pfn() has three occurrences across the codebase:
>
> 1. Definition in mm/alloc_tag.c:830:
>
> void alloc_tag_add_early_pfn(unsigned long pfn, unsigned int alloc_flags)
>
> 2. Declaration in include/linux/alloc_tag.h:166:
>
> void alloc_tag_add_early_pfn(unsigned long pfn, gfp_t gfp_flags)
>
> 3. Static inline stub in include/linux/alloc_tag.h:170:
>
> static inline void alloc_tag_add_early_pfn(unsigned long pfn, gfp_t 
> gfp_flags) {}
>
> This patch updates the definition in alloc_tag.c to take unsigned int 
> alloc_flags,
>
> but the two declarations in alloc_tag.h are left with the old gfp_t 
> gfp_flags signature
>
> These should be updated to match.

Yeah ditto, sorry about this and thanks for the review.