From: Matthew Wilcox <willy@infradead.org>
To: linux-fsdevel@vger.kernel.org
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.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
Subject: [PATCH v8 05/25] mm: Add new readahead_control API
Date: Tue, 25 Feb 2020 13:48:18 -0800 [thread overview]
Message-ID: <20200225214838.30017-6-willy@infradead.org> (raw)
In-Reply-To: <20200225214838.30017-1-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>
---
include/linux/pagemap.h | 140 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 140 insertions(+)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 24894b9b90c9..232892d37071 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -638,6 +638,146 @@ 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) >>
--
2.25.0
next prev parent reply other threads:[~2020-02-25 21:50 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-25 21:48 [PATCH v8 00/25] Change readahead API Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 01/25] mm: Move readahead prototypes from mm.h Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 02/25] mm: Return void from various readahead functions Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 03/25] mm: Ignore return value of ->readpages Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 04/25] mm: Move readahead nr_pages check into read_pages Matthew Wilcox
2020-02-25 21:48 ` Matthew Wilcox [this message]
2020-02-26 17:01 ` [PATCH v8 05/25] mm: Add new readahead_control API Christoph Hellwig
2020-02-25 21:48 ` [PATCH v8 06/25] mm: Use readahead_control to pass arguments Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 07/25] mm: Rename various 'offset' parameters to 'index' Matthew Wilcox
2020-02-26 17:13 ` Zi Yan
2020-02-25 21:48 ` [PATCH v8 08/25] mm: rename readahead loop variable to 'i' Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 09/25] mm: Remove 'page_offset' from readahead loop Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 10/25] mm: Put readahead pages in cache earlier Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 11/25] mm: Add readahead address space operation Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 12/25] mm: Move end_index check out of readahead loop Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 13/25] mm: Add page_cache_readahead_unbounded Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 14/25] mm: Document why we don't set PageReadahead Matthew Wilcox
2020-02-26 17:03 ` Christoph Hellwig
2020-02-25 21:48 ` [PATCH v8 15/25] mm: Use memalloc_nofs_save in readahead path Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 16/25] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 17/25] btrfs: Convert from readpages to readahead Matthew Wilcox
2020-02-26 17:05 ` Christoph Hellwig
2020-02-28 14:08 ` David Sterba
2020-02-25 21:48 ` [PATCH v8 18/25] erofs: Convert uncompressed files " Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 19/25] erofs: Convert compressed " Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 20/25] ext4: Convert " Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 21/25] ext4: Pass the inode to ext4_mpage_readpages Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 22/25] f2fs: Convert from readpages to readahead Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 23/25] f2fs: Pass the inode to f2fs_mpage_readpages Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 24/25] fuse: Convert from readpages to readahead Matthew Wilcox
2020-02-25 21:48 ` [PATCH v8 25/25] iomap: " Matthew Wilcox
2020-02-26 17:04 ` Darrick J. Wong
2020-02-26 17:07 ` Christoph Hellwig
2020-02-26 17:10 ` Darrick J. Wong
2020-02-26 17:07 ` Christoph Hellwig
2020-03-19 10:20 ` [PATCH v8 00/25] Change readahead API Christoph Hellwig
2020-03-19 11:57 ` Matthew Wilcox
2020-03-19 11:49 ` William Kucharski
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