Commit 46df8e73 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Andrew Morton
Browse files

mm: free up PG_slab 

Reclaim the Slab page flag by using a spare bit in PageType.  We are
perennially short of page flags for various purposes, and now that the
original SLAB allocator has been retired, SLUB does not use the
mapcount/page_type field.  This lets us remove a number of special cases
for ignoring mapcount on Slab pages.

[willy@infradead.org: update vmcoreinfo]
  Link: https://lkml.kernel.org/r/ZgGV-O8WYQ_83kxp@casper.infradead.org
Link: https://lkml.kernel.org/r/20240321142448.1645400-8-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 8682a7be

include/linux/page-flags.h

+17 −4
Original line number Diff line number Diff line
@@ -109,7 +109,6 @@ enum pageflags { 
	PG_active,

	PG_workingset,

	PG_error,

	PG_slab,

	PG_owner_priv_1,	/* Owner use. If pagecache, fs may use*/

	PG_arch_1,

	PG_reserved,
@@ -524,7 +523,6 @@ PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD) 
	TESTCLEARFLAG(Active, active, PF_HEAD)

PAGEFLAG(Workingset, workingset, PF_HEAD)

	TESTCLEARFLAG(Workingset, workingset, PF_HEAD)

__PAGEFLAG(Slab, slab, PF_NO_TAIL)

PAGEFLAG(Checked, checked, PF_NO_COMPOUND)	   /* Used by some filesystems */



/* Xen */
@@ -931,7 +929,7 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned) 
#endif



/*

 * For pages that are never mapped to userspace (and aren't PageSlab),

 * For pages that are never mapped to userspace,

 * page_type may be used.  Because it is initialised to -1, we invert the

 * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and

 * __ClearPageFoo *sets* the bit used for PageFoo.  We reserve a few high and
@@ -947,6 +945,7 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned) 
#define PG_table	0x00000200

#define PG_guard	0x00000400

#define PG_hugetlb	0x00000800

#define PG_slab		0x00001000



#define PageType(page, flag)						\

	((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
@@ -1041,6 +1040,20 @@ PAGE_TYPE_OPS(Table, table, pgtable) 
 */

PAGE_TYPE_OPS(Guard, guard, guard)



FOLIO_TYPE_OPS(slab, slab)



/**

 * PageSlab - Determine if the page belongs to the slab allocator

 * @page: The page to test.

 *

 * Context: Any context.

 * Return: True for slab pages, false for any other kind of page.

 */

static inline bool PageSlab(const struct page *page)

{

	return folio_test_slab(page_folio(page));

}



#ifdef CONFIG_HUGETLB_PAGE

FOLIO_TYPE_OPS(hugetlb, hugetlb)

#else
@@ -1121,7 +1134,7 @@ static __always_inline void __ClearPageAnonExclusive(struct page *page) 
	(1UL << PG_lru		| 1UL << PG_locked	|	\

	 1UL << PG_private	| 1UL << PG_private_2	|	\

	 1UL << PG_writeback	| 1UL << PG_reserved	|	\

	 1UL << PG_slab		| 1UL << PG_active 	|	\

	 1UL << PG_active 	|				\

	 1UL << PG_unevictable	| __PG_MLOCKED | LRU_GEN_MASK)



/*

include/trace/events/mmflags.h

+1 −1
Original line number Diff line number Diff line
@@ -107,7 +107,6 @@ 
	DEF_PAGEFLAG_NAME(lru),						\

	DEF_PAGEFLAG_NAME(active),					\

	DEF_PAGEFLAG_NAME(workingset),					\

	DEF_PAGEFLAG_NAME(slab),					\

	DEF_PAGEFLAG_NAME(owner_priv_1),				\

	DEF_PAGEFLAG_NAME(arch_1),					\

	DEF_PAGEFLAG_NAME(reserved),					\
@@ -135,6 +134,7 @@ IF_HAVE_PG_ARCH_X(arch_3) 
#define DEF_PAGETYPE_NAME(_name) { PG_##_name, __stringify(_name) }



#define __def_pagetype_names						\

	DEF_PAGETYPE_NAME(slab),					\

	DEF_PAGETYPE_NAME(hugetlb),					\

	DEF_PAGETYPE_NAME(offline),					\

	DEF_PAGETYPE_NAME(guard),					\

kernel/vmcore_info.c

+2 −1
Original line number Diff line number Diff line
@@ -198,7 +198,8 @@ static int __init crash_save_vmcoreinfo_init(void) 
	VMCOREINFO_NUMBER(PG_private);

	VMCOREINFO_NUMBER(PG_swapcache);

	VMCOREINFO_NUMBER(PG_swapbacked);

	VMCOREINFO_NUMBER(PG_slab);

#define PAGE_SLAB_MAPCOUNT_VALUE	(~PG_slab)

	VMCOREINFO_NUMBER(PAGE_SLAB_MAPCOUNT_VALUE);

#ifdef CONFIG_MEMORY_FAILURE

	VMCOREINFO_NUMBER(PG_hwpoison);

#endif

mm/memory-failure.c

+0 −9
Original line number Diff line number Diff line
@@ -1251,7 +1251,6 @@ static int me_huge_page(struct page_state *ps, struct page *p) 
#define mlock		(1UL << PG_mlocked)

#define lru		(1UL << PG_lru)

#define head		(1UL << PG_head)

#define slab		(1UL << PG_slab)

#define reserved	(1UL << PG_reserved)



static struct page_state error_states[] = {
@@ -1261,13 +1260,6 @@ static struct page_state error_states[] = { 
	 * PG_buddy pages only make a small fraction of all free pages.

	 */



	/*

	 * Could in theory check if slab page is free or if we can drop

	 * currently unused objects without touching them. But just

	 * treat it as standard kernel for now.

	 */

	{ slab,		slab,		MF_MSG_SLAB,	me_kernel },



	{ head,		head,		MF_MSG_HUGE,		me_huge_page },



	{ sc|dirty,	sc|dirty,	MF_MSG_DIRTY_SWAPCACHE,	me_swapcache_dirty },
@@ -1294,7 +1286,6 @@ static struct page_state error_states[] = { 
#undef mlock

#undef lru

#undef head

#undef slab

#undef reserved



static void update_per_node_mf_stats(unsigned long pfn,

mm/slab.h

+1 −1
Original line number Diff line number Diff line
@@ -84,8 +84,8 @@ struct slab { 
		};

		struct rcu_head rcu_head;

	};

	unsigned int __unused;



	unsigned int __page_type;

	atomic_t __page_refcount;

#ifdef CONFIG_SLAB_OBJ_EXT

	unsigned long obj_exts;