mm: remove the hugetlb field from struct page

Patch series "Get rid of tail page fields".

Continue the shrinkage of the struct page definition by getting rid of the
'first tail page' and 'second tail page' fields.  I originally did this
patch set before Hugh's rewrite of the subpages_mapcount, so it needed
substantial updates; hope I didn't miss anything.


This patch (of 28):

commit dad6a5eb(mm,hugetlb: use folio fields in second tail page)
added a transitional hugetlb field to struct page and struct folio to make
room for another int in the first tail of a compound page.  Hugetlb folio
conversions have changed all page users of this field to use the fields
within the folio so struct page no longer needs this hugetlb specific
field.

Link: https://lkml.kernel.org/r/20230111142915.1001531-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20230111142915.1001531-29-willy@infradead.orgSigned-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm_types.h

@@ -141,14 +141,6 @@ struct page {
 		struct {	/* Tail pages of compound page */
 			unsigned long compound_head;	/* Bit zero is set */
 		};
-		struct {	/* Second tail page of hugetlb page */
-			unsigned long _hugetlb_pad_1;	/* compound_head */
-			void *hugetlb_subpool;
-			void *hugetlb_cgroup;
-			void *hugetlb_cgroup_rsvd;
-			void *hugetlb_hwpoison;
-			/* No more space on 32-bit: use third tail if more */
-		};
 		struct {	/* Page table pages */
 			unsigned long _pt_pad_1;	/* compound_head */
 			pgtable_t pmd_huge_pte; /* protected by page->ptl */
@@ -399,10 +391,6 @@ FOLIO_MATCH(compound_head, _head_1);
 			offsetof(struct page, pg) + 2 * sizeof(struct page))
 FOLIO_MATCH(flags, _flags_2);
 FOLIO_MATCH(compound_head, _head_2);
-FOLIO_MATCH(hugetlb_subpool, _hugetlb_subpool);
-FOLIO_MATCH(hugetlb_cgroup, _hugetlb_cgroup);
-FOLIO_MATCH(hugetlb_cgroup_rsvd, _hugetlb_cgroup_rsvd);
-FOLIO_MATCH(hugetlb_hwpoison, _hugetlb_hwpoison);
 #undef FOLIO_MATCH
 
 /*