Messages in this thread | | | Date | Thu, 5 Jan 2023 04:02:47 +0000 | From | Aaron Thompson <> | Subject | Re: [PATCH 1/1] mm: Always release pages to the buddy allocator in memblock_free_late(). |
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Hi Mike,
On 2023-01-04 11:34, Mike Rapoport wrote: > Hi, > > On Wed, Jan 04, 2023 at 07:43:36AM +0000, Aaron Thompson wrote: >> If CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, memblock_free_pages() >> only releases pages to the buddy allocator if they are not in the >> deferred range. This is correct for free pages (as defined by >> for_each_free_mem_pfn_range_in_zone()) because free pages in the >> deferred range will be initialized and released as part of the >> deferred >> init process. memblock_free_pages() is called by memblock_free_late(), >> which is used to free reserved ranges after memblock_free_all() has >> run. memblock_free_all() initializes all pages in reserved ranges, and > > To be precise, memblock_free_all() frees pages, or releases them to the > pages allocator, rather than initializes.
As you mentioned in the comment below, whether memblock_free_all() does any initializing depends on the particular deferred init situation. memblock_free_all() does ultimately call init_reserved_page() for every reserved page (via reserve_bootmem_region()), but that only actually initializes the page if it's in the deferred range. In either case, all I was trying to say here is that we can be certain that all reserved pages have been initialized after memblock_free_all() has run, so I'll rephrase that.
>> accordingly, those pages are not touched by the deferred init >> process. This means that currently, if the pages that >> memblock_free_late() intends to release are in the deferred range, >> they >> will never be released to the buddy allocator. They will forever be >> reserved. >> >> In addition, memblock_free_pages() calls kmsan_memblock_free_pages(), >> which is also correct for free pages but is not correct for reserved >> pages. KMSAN metadata for reserved pages is initialized by >> kmsan_init_shadow(), which runs shortly before memblock_free_all(). >> >> For both of these reasons, memblock_free_pages() should only be called >> for free pages, and memblock_free_late() should call >> __free_pages_core() >> directly instead. > > Overall looks fine to me and I couldn't spot potential issues. > > I'd appreciate if you add a paragraph about the actual issue with EFI > boot > you described in the cover letter to the commit message.
Sure, will do.
>> Fixes: 3a80a7fa7989 ("mm: meminit: initialise a subset of struct pages >> if CONFIG_DEFERRED_STRUCT_PAGE_INIT is set") >> Signed-off-by: Aaron Thompson <dev@aaront.org> >> --- >> mm/memblock.c | 2 +- >> tools/testing/memblock/internal.h | 4 ++++ >> 2 files changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/mm/memblock.c b/mm/memblock.c >> index 511d4783dcf1..56a5b6086c50 100644 >> --- a/mm/memblock.c >> +++ b/mm/memblock.c >> @@ -1640,7 +1640,7 @@ void __init memblock_free_late(phys_addr_t base, >> phys_addr_t size) >> end = PFN_DOWN(base + size); >> >> for (; cursor < end; cursor++) { >> - memblock_free_pages(pfn_to_page(cursor), cursor, 0); >> + __free_pages_core(pfn_to_page(cursor), 0); > > Please add a comment that explains why it is safe to call > __free_pages_core() here. > Something like > > /* > * Reserved pages are always initialized by the end of > * memblock_free_all() either during memmap_init() or, with deferred > * initialization if struct page in reserve_bootmem_region() > */
Will do. Thanks for the review.
>> totalram_pages_inc(); >> } >> } >> diff --git a/tools/testing/memblock/internal.h >> b/tools/testing/memblock/internal.h >> index fdb7f5db7308..85973e55489e 100644 >> --- a/tools/testing/memblock/internal.h >> +++ b/tools/testing/memblock/internal.h >> @@ -15,6 +15,10 @@ bool mirrored_kernelcore = false; >> >> struct page {}; >> >> +void __free_pages_core(struct page *page, unsigned int order) >> +{ >> +} >> + >> void memblock_free_pages(struct page *page, unsigned long pfn, >> unsigned int order) >> { >> -- >> 2.30.2 >>
Thanks, -- Aaron
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