From 46df8e73a4a3f1445f2a8429111e72ede1f4d291 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Thu, 21 Mar 2024 14:24:45 +0000 Subject: [PATCH] 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: Matthew Wilcox (Oracle) Acked-by: David Hildenbrand Cc: Miaohe Lin Cc: Muchun Song Cc: Oscar Salvador Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- include/linux/page-flags.h | 21 +++++++++++++++++---- include/trace/events/mmflags.h | 2 +- kernel/vmcore_info.c | 3 ++- mm/memory-failure.c | 9 --------- mm/slab.h | 2 +- 5 files changed, 21 insertions(+), 16 deletions(-) diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 94eb8a11a321..73e0b17c7728 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -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) /* diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h index d55e53ac91bd..e46d6e82765e 100644 --- a/include/trace/events/mmflags.h +++ b/include/trace/events/mmflags.h @@ -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), \ diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c index 23c125c2e243..1d5eadd9dd61 100644 --- a/kernel/vmcore_info.c +++ b/kernel/vmcore_info.c @@ -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 diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 9e62a00b46dd..0a7a8a4ba421 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -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, diff --git a/mm/slab.h b/mm/slab.h index 65db525e93af..1343bfa12cee 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -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;