The patch titled
Subject: mm: add new readahead_control API
has been added to the -mm tree. Its filename is
mm-add-new-readahead_control-api.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-add-new-readahead_control-api.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-add-new-readahead_control-api.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: add new readahead_control API
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.
Link: http://lkml.kernel.org/r/20200414150233.24495-6-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: Chao Yu <yuchao0@xxxxxxxxxx>
Cc: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
Cc: Gao Xiang <gaoxiang25@xxxxxxxxxx>
Cc: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/pagemap.h | 140 ++++++++++++++++++++++++++++++++++++++
1 file changed, 140 insertions(+)
--- a/include/linux/pagemap.h~mm-add-new-readahead_control-api
+++ a/include/linux/pagemap.h
@@ -639,6 +639,146 @@ static inline int add_to_page_cache(stru
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) >>
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-move-readahead-prototypes-from-mmh.patch
mm-return-void-from-various-readahead-functions.patch
mm-ignore-return-value-of-readpages.patch
mm-move-readahead-nr_pages-check-into-read_pages.patch
mm-add-new-readahead_control-api.patch
mm-use-readahead_control-to-pass-arguments.patch
mm-rename-various-offset-parameters-to-index.patch
mm-rename-readahead-loop-variable-to-i.patch
mm-remove-page_offset-from-readahead-loop.patch
mm-put-readahead-pages-in-cache-earlier.patch
mm-add-readahead-address-space-operation.patch
mm-move-end_index-check-out-of-readahead-loop.patch
mm-add-page_cache_readahead_unbounded.patch
mm-document-why-we-dont-set-pagereadahead.patch
mm-use-memalloc_nofs_save-in-readahead-path.patch
fs-convert-mpage_readpages-to-mpage_readahead.patch
btrfs-convert-from-readpages-to-readahead.patch
erofs-convert-uncompressed-files-from-readpages-to-readahead.patch
erofs-convert-compressed-files-from-readpages-to-readahead.patch
ext4-convert-from-readpages-to-readahead.patch
ext4-pass-the-inode-to-ext4_mpage_readpages.patch
f2fs-convert-from-readpages-to-readahead.patch
f2fs-pass-the-inode-to-f2fs_mpage_readpages.patch
fuse-convert-from-readpages-to-readahead.patch
iomap-convert-from-readpages-to-readahead.patch
