From: Matthew Wilcox <willy@infradead.org> To: Andrew Morton <akpm@linux-foundation.org> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, ocfs2-devel@oss.oracle.com, linux-xfs@vger.kernel.org, Christoph Hellwig <hch@lst.de>, William Kucharski <william.kucharski@oracle.com> Subject: [PATCH v11 05/25] mm: Add new readahead_control API Date: Tue, 14 Apr 2020 08:02:13 -0700 Message-ID: <20200414150233.24495-6-willy@infradead.org> (raw) In-Reply-To: <20200414150233.24495-1-willy@infradead.org> From: "Matthew Wilcox (Oracle)" <willy@infradead.org> Filesystems which implement the upcoming ->readahead method will get their pages by calling readahead_page() or readahead_page_batch(). These functions support large pages, even though none of the filesystems to be converted do yet. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: William Kucharski <william.kucharski@oracle.com> --- include/linux/pagemap.h | 140 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 140 insertions(+) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 6c61535aa7ff..a6eccfd2c80b 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -639,6 +639,146 @@ static inline int add_to_page_cache(struct page *page, return error; } +/** + * struct readahead_control - Describes a readahead request. + * + * A readahead request is for consecutive pages. Filesystems which + * implement the ->readahead method should call readahead_page() or + * readahead_page_batch() in a loop and attempt to start I/O against + * each page in the request. + * + * Most of the fields in this struct are private and should be accessed + * by the functions below. + * + * @file: The file, used primarily by network filesystems for authentication. + * May be NULL if invoked internally by the filesystem. + * @mapping: Readahead this filesystem object. + */ +struct readahead_control { + struct file *file; + struct address_space *mapping; +/* private: use the readahead_* accessors instead */ + pgoff_t _index; + unsigned int _nr_pages; + unsigned int _batch_count; +}; + +/** + * readahead_page - Get the next page to read. + * @rac: The current readahead request. + * + * Context: The page is locked and has an elevated refcount. The caller + * should decreases the refcount once the page has been submitted for I/O + * and unlock the page once all I/O to that page has completed. + * Return: A pointer to the next page, or %NULL if we are done. + */ +static inline struct page *readahead_page(struct readahead_control *rac) +{ + struct page *page; + + BUG_ON(rac->_batch_count > rac->_nr_pages); + rac->_nr_pages -= rac->_batch_count; + rac->_index += rac->_batch_count; + + if (!rac->_nr_pages) { + rac->_batch_count = 0; + return NULL; + } + + page = xa_load(&rac->mapping->i_pages, rac->_index); + VM_BUG_ON_PAGE(!PageLocked(page), page); + rac->_batch_count = hpage_nr_pages(page); + + return page; +} + +static inline unsigned int __readahead_batch(struct readahead_control *rac, + struct page **array, unsigned int array_sz) +{ + unsigned int i = 0; + XA_STATE(xas, &rac->mapping->i_pages, 0); + struct page *page; + + BUG_ON(rac->_batch_count > rac->_nr_pages); + rac->_nr_pages -= rac->_batch_count; + rac->_index += rac->_batch_count; + rac->_batch_count = 0; + + xas_set(&xas, rac->_index); + rcu_read_lock(); + xas_for_each(&xas, page, rac->_index + rac->_nr_pages - 1) { + VM_BUG_ON_PAGE(!PageLocked(page), page); + VM_BUG_ON_PAGE(PageTail(page), page); + array[i++] = page; + rac->_batch_count += hpage_nr_pages(page); + + /* + * The page cache isn't using multi-index entries yet, + * so the xas cursor needs to be manually moved to the + * next index. This can be removed once the page cache + * is converted. + */ + if (PageHead(page)) + xas_set(&xas, rac->_index + rac->_batch_count); + + if (i == array_sz) + break; + } + rcu_read_unlock(); + + return i; +} + +/** + * readahead_page_batch - Get a batch of pages to read. + * @rac: The current readahead request. + * @array: An array of pointers to struct page. + * + * Context: The pages are locked and have an elevated refcount. The caller + * should decreases the refcount once the page has been submitted for I/O + * and unlock the page once all I/O to that page has completed. + * Return: The number of pages placed in the array. 0 indicates the request + * is complete. + */ +#define readahead_page_batch(rac, array) \ + __readahead_batch(rac, array, ARRAY_SIZE(array)) + +/** + * readahead_pos - The byte offset into the file of this readahead request. + * @rac: The readahead request. + */ +static inline loff_t readahead_pos(struct readahead_control *rac) +{ + return (loff_t)rac->_index * PAGE_SIZE; +} + +/** + * readahead_length - The number of bytes in this readahead request. + * @rac: The readahead request. + */ +static inline loff_t readahead_length(struct readahead_control *rac) +{ + return (loff_t)rac->_nr_pages * PAGE_SIZE; +} + +/** + * readahead_index - The index of the first page in this readahead request. + * @rac: The readahead request. + */ +static inline pgoff_t readahead_index(struct readahead_control *rac) +{ + return rac->_index; +} + +/** + * readahead_count - The number of pages in this readahead request. + * @rac: The readahead request. + */ +static inline unsigned int readahead_count(struct readahead_control *rac) +{ + return rac->_nr_pages; +} + static inline unsigned long dir_pages(struct inode *inode) { return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >> -- 2.25.1
next prev parent reply index Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-04-14 15:02 [PATCH v11 00/25] Change readahead API Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 01/25] mm: Move readahead prototypes from mm.h Matthew Wilcox 2020-04-15 9:10 ` Johannes Thumshirn 2020-04-14 15:02 ` [PATCH v11 02/25] mm: Return void from various readahead functions Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 03/25] mm: Ignore return value of ->readpages Matthew Wilcox 2020-04-15 9:17 ` Johannes Thumshirn 2020-04-14 15:02 ` [PATCH v11 04/25] mm: Move readahead nr_pages check into read_pages Matthew Wilcox 2020-04-15 9:19 ` Johannes Thumshirn 2020-04-14 15:02 ` Matthew Wilcox [this message] 2020-04-15 1:17 ` [PATCH v11 05/25] mm: Add new readahead_control API Andrew Morton 2020-04-15 2:18 ` Matthew Wilcox 2020-04-15 4:56 ` Andrew Morton 2020-04-15 11:22 ` Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 06/25] mm: Use readahead_control to pass arguments Matthew Wilcox 2020-04-15 9:30 ` Johannes Thumshirn 2020-04-14 15:02 ` [PATCH v11 07/25] mm: Rename various 'offset' parameters to 'index' Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 08/25] mm: rename readahead loop variable to 'i' Matthew Wilcox 2020-04-15 9:31 ` Johannes Thumshirn 2020-04-14 15:02 ` [PATCH v11 09/25] mm: Remove 'page_offset' from readahead loop Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 10/25] mm: Put readahead pages in cache earlier Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 11/25] mm: Add readahead address space operation Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 12/25] mm: Move end_index check out of readahead loop Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 13/25] mm: Add page_cache_readahead_unbounded Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 14/25] mm: Document why we don't set PageReadahead Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 15/25] mm: Use memalloc_nofs_save in readahead path Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 16/25] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox 2020-06-16 22:36 ` [Cluster-devel] " Andreas Gruenbacher 2020-06-17 0:32 ` Matthew Wilcox 2020-06-17 0:57 ` Andreas Grünbacher 2020-06-17 2:21 ` Matthew Wilcox 2020-06-18 12:46 ` Andreas Gruenbacher 2020-06-18 15:03 ` Matthew Wilcox 2020-06-18 16:40 ` Andreas Gruenbacher 2020-04-14 15:02 ` [PATCH v11 17/25] btrfs: Convert from readpages to readahead Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 18/25] erofs: Convert uncompressed files " Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 19/25] erofs: Convert compressed " Matthew Wilcox 2020-04-21 5:42 ` Andrew Morton 2020-04-21 7:28 ` Gao Xiang 2020-04-14 15:02 ` [PATCH v11 20/25] ext4: Convert " Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 21/25] ext4: Pass the inode to ext4_mpage_readpages Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 22/25] f2fs: Convert from readpages to readahead Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 23/25] f2fs: Pass the inode to f2fs_mpage_readpages Matthew Wilcox 2020-04-14 15:02 ` [PATCH v11 24/25] fuse: Convert from readpages to readahead Matthew Wilcox 2020-04-20 11:14 ` Miklos Szeredi 2020-04-20 11:43 ` Matthew Wilcox 2020-04-20 11:54 ` Miklos Szeredi 2020-04-14 15:02 ` [PATCH v11 25/25] iomap: " Matthew Wilcox
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