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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
Subject: [PATCH v2 08/27] mm: Handle per-folio private data
Date: Mon, 18 Jan 2021 17:01:29 +0000
Message-ID: <20210118170148.3126186-9-willy@infradead.org> (raw)
In-Reply-To: <20210118170148.3126186-1-willy@infradead.org>

Add folio_private() and set_folio_private() which mirror page_private()
and set_page_private() -- ie folio private data is the same as page
private data.

Turn attach_page_private() into attach_folio_private() and reimplement
attach_page_private() as a wrapper.  No filesystem which uses page private
data currently supports compound pages, so we're free to define the rules.
attach_page_private() may only be called on a head page; if you want
to add private data to a tail page, you can call set_page_private()
directly (and shouldn't increment the page refcount!  That should be
done when adding private data to the head page / folio).

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/mm_types.h | 16 ++++++++++++++
 include/linux/pagemap.h  | 48 ++++++++++++++++++++++++----------------
 2 files changed, 45 insertions(+), 19 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 875dc6cd6ad2..750184130074 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -258,6 +258,12 @@ static inline atomic_t *compound_pincount_ptr(struct page *page)
 #define PAGE_FRAG_CACHE_MAX_SIZE	__ALIGN_MASK(32768, ~PAGE_MASK)
 #define PAGE_FRAG_CACHE_MAX_ORDER	get_order(PAGE_FRAG_CACHE_MAX_SIZE)
 
+/*
+ * page_private can be used on tail pages.  However, PagePrivate is only
+ * checked by the VM on the head page.  So page_private on the tail pages
+ * should be used for data that's ancillary to the head page (eg attaching
+ * buffer heads to tail pages after attaching buffer heads to the head page)
+ */
 #define page_private(page)		((page)->private)
 
 static inline void set_page_private(struct page *page, unsigned long private)
@@ -265,6 +271,16 @@ static inline void set_page_private(struct page *page, unsigned long private)
 	page->private = private;
 }
 
+static inline unsigned long folio_private(struct folio *folio)
+{
+	return folio->page.private;
+}
+
+static inline void set_folio_private(struct folio *folio, unsigned long v)
+{
+	folio->page.private = v;
+}
+
 struct page_frag_cache {
 	void * va;
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 4317f34866c7..a739ada01d27 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -245,42 +245,52 @@ static inline int page_cache_add_speculative(struct page *page, int count)
 }
 
 /**
- * attach_page_private - Attach private data to a page.
- * @page: Page to attach data to.
- * @data: Data to attach to page.
+ * attach_folio_private - Attach private data to a folio.
+ * @folio: Folio to attach data to.
+ * @data: Data to attach to folio.
  *
- * Attaching private data to a page increments the page's reference count.
- * The data must be detached before the page will be freed.
+ * Attaching private data to a folio increments the page's reference count.
+ * The data must be detached before the folio will be freed.
  */
-static inline void attach_page_private(struct page *page, void *data)
+static inline void attach_folio_private(struct folio *folio, void *data)
 {
-	get_page(page);
-	set_page_private(page, (unsigned long)data);
-	SetPagePrivate(page);
+	get_folio(folio);
+	set_folio_private(folio, (unsigned long)data);
+	SetFolioPrivate(folio);
 }
 
 /**
- * detach_page_private - Detach private data from a page.
- * @page: Page to detach data from.
+ * detach_folio_private - Detach private data from a folio.
+ * @folio: Folio to detach data from.
  *
- * Removes the data that was previously attached to the page and decrements
+ * Removes the data that was previously attached to the folio and decrements
  * the refcount on the page.
  *
- * Return: Data that was attached to the page.
+ * Return: Data that was attached to the folio.
  */
-static inline void *detach_page_private(struct page *page)
+static inline void *detach_folio_private(struct folio *folio)
 {
-	void *data = (void *)page_private(page);
+	void *data = (void *)folio_private(folio);
 
-	if (!PagePrivate(page))
+	if (!FolioPrivate(folio))
 		return NULL;
-	ClearPagePrivate(page);
-	set_page_private(page, 0);
-	put_page(page);
+	ClearFolioPrivate(folio);
+	set_folio_private(folio, 0);
+	put_folio(folio);
 
 	return data;
 }
 
+static inline void attach_page_private(struct page *page, void *data)
+{
+	attach_folio_private((struct folio *)page, data);
+}
+
+static inline void *detach_page_private(struct page *page)
+{
+	return detach_folio_private((struct folio *)page);
+}
+
 #ifdef CONFIG_NUMA
 extern struct page *__page_cache_alloc(gfp_t gfp);
 #else
-- 
2.29.2


  parent reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-18 17:01 [PATCH v2 00/27] Page folios Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 01/27] mm: Introduce struct folio Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 02/27] mm: Add folio_pgdat Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 03/27] mm/vmstat: Add folio stat wrappers Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 04/27] mm/debug: Add VM_BUG_ON_FOLIO and VM_WARN_ON_ONCE_FOLIO Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 05/27] mm: Add put_folio Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 06/27] mm: Add get_folio Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 07/27] mm: Create FolioFlags Matthew Wilcox (Oracle)
2021-01-18 17:01 ` Matthew Wilcox (Oracle) [this message]
2021-01-18 17:01 ` [PATCH v2 09/27] mm: Add folio_index, folio_page and folio_contains Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 10/27] mm/util: Add folio_mapping and folio_file_mapping Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 11/27] mm/memcg: Add folio_memcg, lock_folio_memcg and unlock_folio_memcg Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 12/27] mm/memcg: Add mem_cgroup_folio_lruvec Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 13/27] mm: Add unlock_folio Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 14/27] mm: Add lock_folio Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 15/27] mm: Add lock_folio_killable Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 16/27] mm: Convert lock_page_async to lock_folio_async Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 17/27] mm/filemap: Convert lock_page_for_iocb to lock_folio_for_iocb Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 18/27] mm/filemap: Convert wait_on_page_locked_async to wait_on_folio_locked_async Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 19/27] mm/filemap: Convert end_page_writeback to end_folio_writeback Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 20/27] mm: Convert wait_on_page_bit to wait_on_folio_bit Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 21/27] mm: Add wait_for_stable_folio and wait_on_folio_writeback Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 22/27] mm: Add wait_on_folio_locked & wait_on_folio_locked_killable Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 23/27] mm: Convert lock_page_or_retry to lock_folio_or_retry Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 24/27] mm/filemap: Convert wake_up_page_bit to wake_up_folio_bit Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 25/27] mm: Convert test_clear_page_writeback to test_clear_folio_writeback Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 26/27] mm/filemap: Convert page wait queues to be folios Matthew Wilcox (Oracle)
2021-01-18 17:01 ` [PATCH v2 27/27] cachefiles: Switch to wait_page_key Matthew Wilcox (Oracle)

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