On 5/1/20 12:10 AM, Andreas Grünbacher wrote:
Hi, Am Do., 30. Apr. 2020 um 23:56 Uhr schrieb Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>: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/clear_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 the new names from Christoph Hellwig. Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> 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 -> 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 | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index a8f7bd8ea1c6..2e515f210b18 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -205,6 +205,41 @@ static inline int page_cache_add_speculative(struct page *page, int count) return __page_cache_add_speculative(page, count); } +/** + * attach_page_private - attach data to page's private field and set PG_private. + * @page: page to be attached and set flag. + * @data: data to attach to page's private field. + * + * Need to take reference as mm.h said "Setting PG_private should also increment + * the refcount". + */ +static inline void attach_page_private(struct page *page, void *data) +{ + get_page(page); + set_page_private(page, (unsigned long)data); + SetPagePrivate(page); +} + +/** + * clear_page_private - clear page's private field and PG_private. + * @page: page to be cleared. + * + * The counterpart function of attach_page_private. + * Return: private data of page or NULL if page doesn't have private data. + */ +static inline void *clear_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; +} +I like this in general, but the name clear_page_private suggests that this might be the inverse operation of set_page_private, which it is not. So maybe this can be renamed to detach_page_private to more clearly indicate that it pairs with attach_page_private?
Yes, the new name is better, thank you! Cheers, Guoqing
