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mm: free up a word in the first tail page

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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>
This commit is contained in:
Matthew Wilcox (Oracle)
2023-08-16 16:11:58 +01:00
committed by Andrew Morton
parent c704ae9797
commit ebc1baf5c9
5 changed files with 11 additions and 12 deletions
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10
include/linux/mm.h
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@@ -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
}