Commit 4eeec8c8 authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm: move hugetlb specific things in folio to page[3] 

Let's just move the hugetlb specific stuff to a separate page, and stop
letting it overlay other fields for now.

This frees up some space in page[2], which we will use on 32bit to free up
some space in page[1].  While we could move these things to page[3]
instead, it's cleaner to just move the hugetlb specific things out of the
way and pack the core-folio stuff as tight as possible.  ...  and we can
minimize the work required in dump_folio.

We can now avoid re-initializing &folio->_deferred_list in hugetlb code.

Hopefully dynamically allocating "strut folio" in the future will further
clean this up.

Link: https://lkml.kernel.org/r/20250303163014.1128035-5-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Andy Lutomirks^H^Hski <luto@kernel.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Michal Koutn <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: tejun heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 4996fc54

include/linux/mm_types.h

+17 −10
Original line number Diff line number Diff line
@@ -407,20 +407,23 @@ struct folio { 
			unsigned long _flags_2;

			unsigned long _head_2;

	/* public: */

			void *_hugetlb_subpool;

			void *_hugetlb_cgroup;

			void *_hugetlb_cgroup_rsvd;

			void *_hugetlb_hwpoison;

			struct list_head _deferred_list;

	/* private: the union with struct page is transitional */

		};

		struct page __page_2;

	};

	union {

		struct {

			unsigned long _flags_2a;

			unsigned long _head_2a;

			unsigned long _flags_3;

			unsigned long _head_3;

	/* public: */

			struct list_head _deferred_list;

			void *_hugetlb_subpool;

			void *_hugetlb_cgroup;

			void *_hugetlb_cgroup_rsvd;

			void *_hugetlb_hwpoison;

	/* private: the union with struct page is transitional */

		};

		struct page __page_2;

		struct page __page_3;

	};

};
@@ -457,8 +460,12 @@ FOLIO_MATCH(_refcount, _refcount_1); 
			offsetof(struct page, pg) + 2 * sizeof(struct page))

FOLIO_MATCH(flags, _flags_2);

FOLIO_MATCH(compound_head, _head_2);

FOLIO_MATCH(flags, _flags_2a);

FOLIO_MATCH(compound_head, _head_2a);

#undef FOLIO_MATCH

#define FOLIO_MATCH(pg, fl)						\

	static_assert(offsetof(struct folio, fl) ==			\

			offsetof(struct page, pg) + 3 * sizeof(struct page))

FOLIO_MATCH(flags, _flags_3);

FOLIO_MATCH(compound_head, _head_3);

#undef FOLIO_MATCH



/**

mm/hugetlb.c

+0 −1
Original line number Diff line number Diff line
@@ -1649,7 +1649,6 @@ static void __update_and_free_hugetlb_folio(struct hstate *h, 


	folio_ref_unfreeze(folio, 1);



	INIT_LIST_HEAD(&folio->_deferred_list);

	hugetlb_free_folio(folio);

}

mm/page_alloc.c

+5 −0
Original line number Diff line number Diff line
@@ -971,6 +971,11 @@ static int free_tail_page_prepare(struct page *head_page, struct page *page) 
			goto out;

		}

		break;

	case 3:

		/* the third tail page: hugetlb specifics overlap ->mappings */

		if (IS_ENABLED(CONFIG_HUGETLB_PAGE))

			break;

		fallthrough;

	default:

		if (page->mapping != TAIL_MAPPING) {

			bad_page(page, "corrupted mapping in tail page");