113 lines
3.3 KiB
Diff
113 lines
3.3 KiB
Diff
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
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Subject: [PATCH 24/31] mm: methods for teaching filesystems about PG_swapcache pages
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Patch-mainline: not yet
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In order to teach filesystems to handle swap cache pages, three new page
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functions are introduced:
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pgoff_t page_file_index(struct page *);
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loff_t page_file_offset(struct page *);
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struct address_space *page_file_mapping(struct page *);
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page_file_index() - gives the offset of this page in the file in
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PAGE_CACHE_SIZE blocks. Like page->index is for mapped pages, this function
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also gives the correct index for PG_swapcache pages.
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page_file_offset() - uses page_file_index(), so that it will give the expected
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result, even for PG_swapcache pages.
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page_file_mapping() - gives the mapping backing the actual page; that is for
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swap cache pages it will give swap_file->f_mapping.
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Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
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---
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include/linux/mm.h | 25 +++++++++++++++++++++++++
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include/linux/pagemap.h | 5 +++++
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mm/swapfile.c | 19 +++++++++++++++++++
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3 files changed, 49 insertions(+)
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--- a/include/linux/mm.h
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+++ b/include/linux/mm.h
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@@ -662,6 +662,17 @@ static inline void *page_rmapping(struct
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return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
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}
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+extern struct address_space *__page_file_mapping(struct page *);
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+
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+static inline
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+struct address_space *page_file_mapping(struct page *page)
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+{
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+ if (unlikely(PageSwapCache(page)))
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+ return __page_file_mapping(page);
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+
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+ return page->mapping;
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+}
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+
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static inline int PageAnon(struct page *page)
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{
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return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
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@@ -678,6 +689,20 @@ static inline pgoff_t page_index(struct
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return page->index;
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}
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+extern pgoff_t __page_file_index(struct page *page);
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+
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+/*
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+ * Return the file index of the page. Regular pagecache pages use ->index
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+ * whereas swapcache pages use swp_offset(->private)
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+ */
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+static inline pgoff_t page_file_index(struct page *page)
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+{
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+ if (unlikely(PageSwapCache(page)))
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+ return __page_file_index(page);
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+
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+ return page->index;
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+}
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+
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/*
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* The atomic page->_mapcount, like _count, starts from -1:
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* so that transitions both from it and to it can be tracked,
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--- a/include/linux/pagemap.h
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+++ b/include/linux/pagemap.h
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@@ -281,6 +281,11 @@ static inline loff_t page_offset(struct
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return ((loff_t)page->index) << PAGE_CACHE_SHIFT;
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}
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+static inline loff_t page_file_offset(struct page *page)
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+{
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+ return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT;
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+}
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+
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static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
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unsigned long address)
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{
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--- a/mm/swapfile.c
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+++ b/mm/swapfile.c
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@@ -2247,6 +2247,25 @@ struct swap_info_struct *page_swap_info(
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}
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/*
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+ * out-of-line __page_file_ methods to avoid include hell.
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+ */
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+
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+struct address_space *__page_file_mapping(struct page *page)
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+{
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+ VM_BUG_ON(!PageSwapCache(page));
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+ return page_swap_info(page)->swap_file->f_mapping;
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+}
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+EXPORT_SYMBOL_GPL(__page_file_mapping);
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+
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+pgoff_t __page_file_index(struct page *page)
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+{
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+ swp_entry_t swap = { .val = page_private(page) };
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+ VM_BUG_ON(!PageSwapCache(page));
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+ return swp_offset(swap);
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+}
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+EXPORT_SYMBOL_GPL(__page_file_index);
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+
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+/*
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* swap_lock prevents swap_map being freed. Don't grab an extra
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* reference on the swaphandle, it doesn't matter if it becomes unused.
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*/
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