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From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
	linux-kernel@vger.kernel.org, Jeff Layton <jlayton@kernel.org>
Subject: [PATCH v9 09/96] mm: Introduce struct folio
Date: Wed,  5 May 2021 16:05:01 +0100	[thread overview]
Message-ID: <20210505150628.111735-10-willy@infradead.org> (raw)
In-Reply-To: <20210505150628.111735-1-willy@infradead.org>

A struct folio is a new abstraction to replace the venerable struct page.
A function which takes a struct folio argument declares that it will
operate on the entire (possibly compound) page, not just PAGE_SIZE bytes.
In return, the caller guarantees that the pointer it is passing does
not point to a tail page.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Jeff Layton <jlayton@kernel.org>
---
 Documentation/core-api/mm-api.rst |  1 +
 include/linux/mm.h                | 74 +++++++++++++++++++++++++++++++
 include/linux/mm_types.h          | 60 +++++++++++++++++++++++++
 include/linux/page-flags.h        | 27 +++++++++++
 4 files changed, 162 insertions(+)

diff --git a/Documentation/core-api/mm-api.rst b/Documentation/core-api/mm-api.rst
index a42f9baddfbf..2a94e6164f80 100644
--- a/Documentation/core-api/mm-api.rst
+++ b/Documentation/core-api/mm-api.rst
@@ -95,6 +95,7 @@ More Memory Management Functions
 .. kernel-doc:: mm/mempolicy.c
 .. kernel-doc:: include/linux/mm_types.h
    :internal:
+.. kernel-doc:: include/linux/page-flags.h
 .. kernel-doc:: include/linux/mm.h
    :internal:
 .. kernel-doc:: include/linux/mmzone.h
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 2327f99b121f..b29c86824e6b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -950,6 +950,20 @@ static inline unsigned int compound_order(struct page *page)
 	return page[1].compound_order;
 }
 
+/**
+ * folio_order - The allocation order of a folio.
+ * @folio: The folio.
+ *
+ * A folio is composed of 2^order pages.  See get_order() for the definition
+ * of order.
+ *
+ * Return: The order of the folio.
+ */
+static inline unsigned int folio_order(struct folio *folio)
+{
+	return compound_order(&folio->page);
+}
+
 static inline bool hpage_pincount_available(struct page *page)
 {
 	/*
@@ -1595,6 +1609,65 @@ static inline void set_page_links(struct page *page, enum zone_type zone,
 #endif
 }
 
+/**
+ * folio_nr_pages - The number of pages in the folio.
+ * @folio: The folio.
+ *
+ * Return: A number which is a power of two.
+ */
+static inline unsigned long folio_nr_pages(struct folio *folio)
+{
+	return compound_nr(&folio->page);
+}
+
+/**
+ * folio_next - Move to the next physical folio.
+ * @folio: The folio we're currently operating on.
+ *
+ * If you have physically contiguous memory which may span more than
+ * one folio (eg a &struct bio_vec), use this function to move from one
+ * folio to the next.  Do not use it if the memory is only virtually
+ * contiguous as the folios are almost certainly not adjacent to each
+ * other.  This is the folio equivalent to writing ``page++``.
+ *
+ * Context: We assume that the folios are refcounted and/or locked at a
+ * higher level and do not adjust the reference counts.
+ * Return: The next struct folio.
+ */
+static inline struct folio *folio_next(struct folio *folio)
+{
+	return (struct folio *)folio_page(folio, folio_nr_pages(folio));
+}
+
+/**
+ * folio_shift - The number of bits covered by this folio.
+ * @folio: The folio.
+ *
+ * A folio contains a number of bytes which is a power-of-two in size.
+ * This function tells you which power-of-two the folio is.
+ *
+ * Context: The caller should have a reference on the folio to prevent
+ * it from being split.  It is not necessary for the folio to be locked.
+ * Return: The base-2 logarithm of the size of this folio.
+ */
+static inline unsigned int folio_shift(struct folio *folio)
+{
+	return PAGE_SHIFT + folio_order(folio);
+}
+
+/**
+ * folio_size - The number of bytes in a folio.
+ * @folio: The folio.
+ *
+ * Context: The caller should have a reference on the folio to prevent
+ * it from being split.  It is not necessary for the folio to be locked.
+ * Return: The number of bytes in this folio.
+ */
+static inline size_t folio_size(struct folio *folio)
+{
+	return PAGE_SIZE << folio_order(folio);
+}
+
 /*
  * Some inline functions in vmstat.h depend on page_zone()
  */
@@ -1699,6 +1772,7 @@ extern void pagefault_out_of_memory(void);
 
 #define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)
 #define offset_in_thp(page, p)	((unsigned long)(p) & (thp_size(page) - 1))
+#define offset_in_folio(folio, p) ((unsigned long)(p) & (folio_size(folio) - 1))
 
 /*
  * Flags passed to show_mem() and show_free_areas() to suppress output in
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5aacc1c10a45..276e358c75d3 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -224,6 +224,66 @@ struct page {
 #endif
 } _struct_page_alignment;
 
+/**
+ * struct folio - Represents a contiguous set of bytes.
+ * @flags: Identical to the page flags.
+ * @lru: Least Recently Used list; tracks how recently this folio was used.
+ * @mapping: The file this page belongs to, or refers to the anon_vma for
+ *    anonymous pages.
+ * @index: Offset within the file, in units of pages.  For anonymous pages,
+ *    this is the index from the beginning of the mmap.
+ * @private: Filesystem per-folio data (see folio_attach_private()).
+ *    Used for swp_entry_t if folio_swapcache().
+ * @_mapcount: Do not access this member directly.  Use folio_mapcount() to
+ *    find out how many times this folio is mapped by userspace.
+ * @_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.
+ *
+ * A folio is a physically, virtually and logically contiguous set
+ * of bytes.  It is a power-of-two in size, and it is aligned to that
+ * same power-of-two.  It is at least as large as %PAGE_SIZE.  If it is
+ * in the page cache, it is at a file offset which is a multiple of that
+ * power-of-two.  It may be mapped into userspace at an address which is
+ * at an arbitrary page offset, but its kernel virtual address is aligned
+ * to its size.
+ */
+struct folio {
+	/* private: don't document the anon union */
+	union {
+		struct {
+	/* public: */
+			unsigned long flags;
+			struct list_head lru;
+			struct address_space *mapping;
+			pgoff_t index;
+			unsigned long private;
+			atomic_t _mapcount;
+			atomic_t _refcount;
+#ifdef CONFIG_MEMCG
+			unsigned long memcg_data;
+#endif
+	/* private: the union with struct page is transitional */
+		};
+		struct page page;
+	};
+};
+
+static_assert(sizeof(struct page) == sizeof(struct folio));
+#define FOLIO_MATCH(pg, fl)						\
+	static_assert(offsetof(struct page, pg) == offsetof(struct folio, fl))
+FOLIO_MATCH(flags, flags);
+FOLIO_MATCH(lru, lru);
+FOLIO_MATCH(compound_head, lru);
+FOLIO_MATCH(index, index);
+FOLIO_MATCH(private, private);
+FOLIO_MATCH(_mapcount, _mapcount);
+FOLIO_MATCH(_refcount, _refcount);
+#ifdef CONFIG_MEMCG
+FOLIO_MATCH(memcg_data, memcg_data);
+#endif
+#undef FOLIO_MATCH
+
 static inline atomic_t *compound_mapcount_ptr(struct page *page)
 {
 	return &page[1].compound_mapcount;
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index d8e26243db25..e069aa8b11b7 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -188,6 +188,33 @@ static inline unsigned long _compound_head(const struct page *page)
 
 #define compound_head(page)	((typeof(page))_compound_head(page))
 
+/**
+ * page_folio - Converts from page to folio.
+ * @p: The page.
+ *
+ * Every page is part of a folio.  This function cannot be called on a
+ * NULL pointer.
+ *
+ * Context: No reference, nor lock is required on @page.  If the caller
+ * does not hold a reference, this call may race with a folio split, so
+ * it should re-check the folio still contains this page after gaining
+ * a reference on the folio.
+ * Return: The folio which contains this page.
+ */
+#define page_folio(p)		(_Generic((p),				\
+	const struct page *:	(const struct folio *)_compound_head(p), \
+	struct page *:		(struct folio *)_compound_head(p)))
+
+/**
+ * folio_page - Return a page from a folio.
+ * @folio: The folio.
+ * @n: The page number to return.
+ *
+ * @n is relative to the start of the folio.  It should be between
+ * 0 and folio_nr_pages(@folio) - 1, but this is not checked for.
+ */
+#define folio_page(folio, n)	nth_page(&(folio)->page, n)
+
 static __always_inline int PageTail(struct page *page)
 {
 	return READ_ONCE(page->compound_head) & 1;
-- 
2.30.2


  parent reply	other threads:[~2021-05-05 15:17 UTC|newest]

Thread overview: 108+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-05 15:04 [PATCH v9 00/96] Memory folios Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 01/96] mm: Optimise nth_page for contiguous memmap Matthew Wilcox (Oracle)
2021-05-05 17:24   ` Vlastimil Babka
2021-05-05 15:04 ` [PATCH v9 02/96] mm: Make __dump_page static Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 03/96] mm/debug: Factor PagePoisoned out of __dump_page Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 04/96] mm/page_owner: Constify dump_page_owner Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 05/96] mm: Make compound_head const-preserving Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 06/96] mm: Constify get_pfnblock_flags_mask and get_pfnblock_migratetype Matthew Wilcox (Oracle)
2021-05-05 15:04 ` [PATCH v9 07/96] mm: Constify page_count and page_ref_count Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 08/96] mm: Fix struct page layout on 32-bit systems Matthew Wilcox (Oracle)
2021-05-05 17:33   ` Vlastimil Babka
2021-05-05 15:05 ` Matthew Wilcox (Oracle) [this message]
2021-05-05 15:05 ` [PATCH v9 10/96] mm: Add folio_pgdat and folio_zone Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 11/96] mm/vmstat: Add functions to account folio statistics Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 12/96] mm/debug: Add VM_BUG_ON_FOLIO and VM_WARN_ON_ONCE_FOLIO Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 13/96] mm: Add folio reference count functions Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 14/96] mm: Add folio_put Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 15/96] mm: Add folio_get Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 16/96] mm: Add folio flag manipulation functions Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 17/96] mm: Add folio_young() and folio_idle() Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 18/96] mm: Handle per-folio private data Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 19/96] mm/filemap: Add folio_index, folio_file_page and folio_contains Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 20/96] mm/filemap: Add folio_next_index Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 21/96] mm/filemap: Add folio_offset and folio_file_offset Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 22/96] mm/util: Add folio_mapping and folio_file_mapping Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 23/96] mm: Add folio_mapcount Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 24/96] mm/memcg: Add folio wrappers for various functions Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 25/96] mm/filemap: Add folio_unlock Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 26/96] mm/filemap: Add folio_lock Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 27/96] mm/filemap: Add folio_lock_killable Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 28/96] mm/filemap: Add __folio_lock_async Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 29/96] mm/filemap: Add __folio_lock_or_retry Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 30/96] mm/filemap: Add folio_wait_locked Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 31/96] mm/swap: Add folio_rotate_reclaimable Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 32/96] mm/filemap: Add folio_end_writeback Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 33/96] mm/writeback: Add folio_wait_writeback Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 34/96] mm/writeback: Add folio_wait_stable Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 35/96] mm/filemap: Add folio_wait_bit Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 36/96] mm/filemap: Add folio_wake_bit Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 37/96] mm/filemap: Convert page wait queues to be folios Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 38/96] mm/filemap: Add folio private_2 functions Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 39/96] fs/netfs: Add folio fscache functions Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 40/96] mm: Add folio_mapped Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 41/96] mm/workingset: Convert workingset_activation to take a folio Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 42/96] mm/swap: Add folio_activate Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 43/96] mm/swap: Add folio_mark_accessed Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 44/96] mm/rmap: Add folio_mkclean Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 45/96] mm: Add kmap_local_folio Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 46/96] mm: Add flush_dcache_folio Matthew Wilcox (Oracle)
2021-05-05 23:35   ` kernel test robot
2021-05-06  2:33     ` Matthew Wilcox
2021-05-05 15:05 ` [PATCH v9 47/96] mm: Add arch_make_folio_accessible Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 48/96] mm/memcg: Remove 'page' parameter to mem_cgroup_charge_statistics Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 49/96] mm/memcg: Use the node id in mem_cgroup_update_tree Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 50/96] mm/memcg: Convert commit_charge to take a folio Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 51/96] mm/memcg: Add folio_charge_cgroup Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 52/96] mm/memcg: Add folio_uncharge_cgroup Matthew Wilcox (Oracle)
2021-05-05 20:24   ` kernel test robot
2021-05-05 15:05 ` [PATCH v9 53/96] mm/memcg: Convert mem_cgroup_track_foreign_dirty_slowpath to folio Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 54/96] mm/writeback: Rename __add_wb_stat to wb_stat_mod Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 55/96] flex_proportions: Allow N events instead of 1 Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 56/96] mm/writeback: Change __wb_writeout_inc to __wb_writeout_add Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 57/96] mm/writeback: Convert test_clear_page_writeback to __folio_end_writeback Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 58/96] mm/writeback: Add folio_start_writeback Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 59/96] mm/writeback: Add folio_mark_dirty Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 60/96] mm/writeback: Use __set_page_dirty in __set_page_dirty_nobuffers Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 61/96] mm/writeback: Add __folio_mark_dirty Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 62/96] mm/writeback: Add filemap_dirty_folio Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 63/96] mm/writeback: Add folio_account_cleaned Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 64/96] mm/writeback: Add folio_cancel_dirty Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 65/96] mm/writeback: Add folio_clear_dirty_for_io Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 66/96] mm/writeback: Add folio_account_redirty Matthew Wilcox (Oracle)
2021-05-05 15:05 ` [PATCH v9 67/96] mm/writeback: Add folio_redirty_for_writepage Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 68/96] mm/filemap: Add i_blocks_per_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 69/96] mm/filemap: Add folio_mkwrite_check_truncate Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 70/96] mm/filemap: Add readahead_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 71/96] block: Add bio_add_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 72/96] block: Add bio_for_each_folio_all Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 73/96] mm/lru: Add folio_lru and folio_is_file_lru Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 74/96] mm/workingset: Convert workingset_refault to take a folio Matthew Wilcox (Oracle)
2021-05-05 20:17   ` kernel test robot
2021-05-05 20:57     ` Matthew Wilcox
2021-05-05 15:06 ` [PATCH v9 75/96] mm/lru: Add folio_add_lru Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 76/96] mm/page_alloc: Add __alloc_folio, __alloc_folio_node and alloc_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 77/96] mm/filemap: Add filemap_alloc_folio Matthew Wilcox (Oracle)
2021-05-06  0:00   ` kernel test robot
2021-05-06  2:28     ` Matthew Wilcox
2021-05-05 15:06 ` [PATCH v9 78/96] mm/filemap: Add folio_add_to_page_cache Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 79/96] mm/filemap: Convert mapping_get_entry to return a folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 80/96] mm/filemap: Add filemap_get_folio and find_get_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 81/96] mm/filemap: Add filemap_get_stable_folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 82/96] iomap: Convert to_iomap_page to take a folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 83/96] iomap: Convert iomap_page_create " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 84/96] iomap: Convert iomap_page_release " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 85/96] iomap: Convert iomap_releasepage to use " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 86/96] iomap: Convert iomap_invalidatepage " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 87/96] iomap: Pass the iomap_page into iomap_set_range_uptodate Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 88/96] iomap: Use folio offsets instead of page offsets Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 89/96] iomap: Convert bio completions to use folios Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 90/96] iomap: Convert readahead and readpage to use a folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 91/96] iomap: Convert iomap_page_mkwrite " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 92/96] iomap: Convert iomap_write_begin and iomap_write_end to folios Matthew Wilcox (Oracle)
2021-05-05 21:36   ` kernel test robot
2021-05-05 22:10     ` Matthew Wilcox
2021-05-05 15:06 ` [PATCH v9 93/96] iomap: Convert iomap_read_inline_data to take a folio Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 94/96] iomap: Convert iomap_write_end_inline " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 95/96] iomap: Convert iomap_add_to_ioend " Matthew Wilcox (Oracle)
2021-05-05 15:06 ` [PATCH v9 96/96] iomap: Convert iomap_do_writepage to use " Matthew Wilcox (Oracle)

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