The logic in attach_page_buffers and __clear_page_buffers are quite
paired, but
1. they are located in different files.
2. attach_page_buffers is implemented in buffer_head.h, so it could be
used by other files. But __clear_page_buffers is static function in
buffer.c and other potential users can't call the function, md-bitmap
even copied the function.
So, introduce the new attach/detach_page_private to replace them. With
the new pair of function, we will remove the usage of attach_page_buffers
and __clear_page_buffers in next patches. Thanks for suggestions about
the function name from Alexander Viro, Andreas Grünbacher, Christoph
Hellwig and Matthew Wilcox.
Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
Cc: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Cc: Yafang Shao <laoar.shao@xxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: linux-raid@xxxxxxxxxxxxxxx
Cc: Chris Mason <clm@xxxxxx>
Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
Cc: David Sterba <dsterba@xxxxxxxx>
Cc: linux-btrfs@xxxxxxxxxxxxxxx
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Cc: Chao Yu <chao@xxxxxxxxxx>
Cc: linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: linux-xfs@xxxxxxxxxxxxxxx
Cc: Anton Altaparmakov <anton@xxxxxxxxxx>
Cc: linux-ntfs-dev@xxxxxxxxxxxxxxxxxxxxx
Cc: Mike Marshall <hubcap@xxxxxxxxxxxx>
Cc: Martin Brandenburg <martin@xxxxxxxxxxxx>
Cc: devel@xxxxxxxxxxxxxxxxxx
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Andreas Dilger <adilger@xxxxxxxxx>
Signed-off-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>
---
RFC V2 -> RFC V3:
1. rename clear_page_private to detach_page_private.
2. updated the comments for the two functions.
RFC -> RFC V2: Address the comments from Christoph Hellwig
1. change function names to attach/clear_page_private and add comments.
2. change the return type of attach_page_private.
include/linux/pagemap.h | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a8f7bd8ea1c6..99dd93188a5e 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -205,6 +205,43 @@ static inline int page_cache_add_speculative(struct page *page, int count)
return __page_cache_add_speculative(page, count);
}
+/**
+ * attach_page_private - Attach private data to a page.
+ * @page: Page to attach data to.
+ * @data: Data to attach to page.
+ *
+ * Attaching private data to a page increments the page's reference count.
+ * The data must be detached before the page will be freed.
+ */
+static inline void attach_page_private(struct page *page, void *data)
+{
+ get_page(page);
+ set_page_private(page, (unsigned long)data);
+ SetPagePrivate(page);
+}
+
+/**
+ * detach_page_private - Detach private data from a page.
+ * @page: Page to detach data from.
+ *
+ * Removes the data that was previously attached to the page and decrements
+ * the refcount on the page.
+ *
+ * Return: Data that was attached to the page.
+ */
+static inline void *detach_page_private(struct page *page)
+{
+ void *data = (void *)page_private(page);
+
+ if (!PagePrivate(page))
+ return NULL;
+ ClearPagePrivate(page);
+ set_page_private(page, 0);
+ put_page(page);
+
+ return data;
+}
+
#ifdef CONFIG_NUMA
extern struct page *__page_cache_alloc(gfp_t gfp);
#else
--
2.17.1
