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mm/gup: Remove an assumption of a contiguous memmap

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This assumption needs the inverse of nth_page(), which is temporarily
named page_nth() until it's renamed later in this series.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
This commit is contained in:
Matthew Wilcox (Oracle) 2022-01-07 13:45:25 -05:00
parent c228afb11a
commit 4c65422901
2 changed files with 4 additions and 2 deletions
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2
include/linux/mm.h
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@ -212,8 +212,10 @@ int overcommit_policy_handler(struct ctl_table *, int, void *, size_t *,
#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
#define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
#define page_nth(head, tail) (page_to_pfn(tail) - page_to_pfn(head))
#else
#define nth_page(page,n) ((page) + (n))
#define page_nth(head, tail) ((tail) - (head))
#endif
/* to align the pointer to the (next) page boundary */

4
mm/gup.c
View File

@ -261,8 +261,8 @@ static inline struct page *compound_range_next(struct page *start,
next = nth_page(start, i);
page = compound_head(next);
if (PageHead(page))
nr = min_t(unsigned int,
page + compound_nr(page) - next, npages - i);
nr = min_t(unsigned int, npages - i,
compound_nr(page) - page_nth(page, next));
*ntails = nr;
return page;