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authorMatthew Wilcox (Oracle) <willy@infradead.org>2023-08-16 16:11:58 +0100
committerAndrew Morton <akpm@linux-foundation.org>2023-08-21 14:28:45 -0700
commitebc1baf5c9b46c2240c580a2fd992b2e48606dfa (patch)
treec85f3ec8285498ef68bc6f63cdf63825647391d4
parentc704ae9797843402436190a6f094a035237fd012 (diff)
mm: free up a word in the first tail page
Store the folio order in the low byte of the flags word in the first tail page. This frees up the word that was being used to store the order and dtor bytes previously. Link: https://lkml.kernel.org/r/20230816151201.3655946-11-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: David Hildenbrand <david@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com> Cc: Yanteng Si <siyanteng@loongson.cn> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--include/linux/mm.h10
-rw-r--r--include/linux/mm_types.h3
-rw-r--r--include/linux/page-flags.h7
-rw-r--r--kernel/crash_core.c1
-rw-r--r--mm/internal.h2
5 files changed, 11 insertions, 12 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 63d573781973..939386e0aeda 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1000,7 +1000,7 @@ struct inode;
* compound_order() can be called without holding a reference, which means
* that niceties like page_folio() don't work. These callers should be
* prepared to handle wild return values. For example, PG_head may be
- * set before _folio_order is initialised, or this may be a tail page.
+ * set before the order is initialised, or this may be a tail page.
* See compaction.c for some good examples.
*/
static inline unsigned int compound_order(struct page *page)
@@ -1009,7 +1009,7 @@ static inline unsigned int compound_order(struct page *page)
if (!test_bit(PG_head, &folio->flags))
return 0;
- return folio->_folio_order;
+ return folio->_flags_1 & 0xff;
}
/**
@@ -1025,7 +1025,7 @@ static inline unsigned int folio_order(struct folio *folio)
{
if (!folio_test_large(folio))
return 0;
- return folio->_folio_order;
+ return folio->_flags_1 & 0xff;
}
#include <linux/huge_mm.h>
@@ -1996,7 +1996,7 @@ static inline long folio_nr_pages(struct folio *folio)
#ifdef CONFIG_64BIT
return folio->_folio_nr_pages;
#else
- return 1L << folio->_folio_order;
+ return 1L << (folio->_flags_1 & 0xff);
#endif
}
@@ -2014,7 +2014,7 @@ static inline unsigned long compound_nr(struct page *page)
#ifdef CONFIG_64BIT
return folio->_folio_nr_pages;
#else
- return 1L << folio->_folio_order;
+ return 1L << (folio->_flags_1 & 0xff);
#endif
}
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 1c5c2349c18e..40afb3bbc309 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -264,7 +264,6 @@ static inline struct page *encoded_page_ptr(struct encoded_page *page)
* @_refcount: Do not access this member directly. Use folio_ref_count()
* to find how many references there are to this folio.
* @memcg_data: Memory Control Group data.
- * @_folio_order: Do not use directly, call folio_order().
* @_entire_mapcount: Do not use directly, call folio_entire_mapcount().
* @_nr_pages_mapped: Do not use directly, call folio_mapcount().
* @_pincount: Do not use directly, call folio_maybe_dma_pinned().
@@ -316,8 +315,8 @@ struct folio {
struct {
unsigned long _flags_1;
unsigned long _head_1;
+ unsigned long _folio_avail;
/* public: */
- unsigned char _folio_order;
atomic_t _entire_mapcount;
atomic_t _nr_pages_mapped;
atomic_t _pincount;
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 46fc05c648ff..638b0a96b4c5 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -184,7 +184,8 @@ enum pageflags {
/*
* Flags only valid for compound pages. Stored in first tail page's
- * flags word.
+ * flags word. Cannot use the first 8 flags or any flag marked as
+ * PF_ANY.
*/
/* At least one page in this folio has the hwpoison flag set */
@@ -1081,8 +1082,8 @@ static __always_inline void __ClearPageAnonExclusive(struct page *page)
* the CHECK_AT_FREE flags above, so need to be cleared.
*/
#define PAGE_FLAGS_SECOND \
- (1UL << PG_has_hwpoisoned | 1UL << PG_hugetlb | \
- 1UL << PG_large_rmappable)
+ (0xffUL /* order */ | 1UL << PG_has_hwpoisoned | \
+ 1UL << PG_hugetlb | 1UL << PG_large_rmappable)
#define PAGE_FLAGS_PRIVATE \
(1UL << PG_private | 1UL << PG_private_2)
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 934dd86e19f5..693445e1f7f6 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -455,7 +455,6 @@ static int __init crash_save_vmcoreinfo_init(void)
VMCOREINFO_OFFSET(page, lru);
VMCOREINFO_OFFSET(page, _mapcount);
VMCOREINFO_OFFSET(page, private);
- VMCOREINFO_OFFSET(folio, _folio_order);
VMCOREINFO_OFFSET(page, compound_head);
VMCOREINFO_OFFSET(pglist_data, node_zones);
VMCOREINFO_OFFSET(pglist_data, nr_zones);
diff --git a/mm/internal.h b/mm/internal.h
index 5c0daea731f3..d1d4bf4e63c0 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -407,7 +407,7 @@ static inline void folio_set_order(struct folio *folio, unsigned int order)
if (WARN_ON_ONCE(!order || !folio_test_large(folio)))
return;
- folio->_folio_order = order;
+ folio->_flags_1 = (folio->_flags_1 & ~0xffUL) | order;
#ifdef CONFIG_64BIT
folio->_folio_nr_pages = 1U << order;
#endif