mm: use readahead_control to pass arguments

In this patch, only between __do_page_cache_readahead() and
read_pages(), but it will be extended in upcoming patches.  The
read_pages() function becomes aops centric, as this makes the most sense
by the end of the patchset.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Gao Xiang <gaoxiang25@huawei.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Link: http://lkml.kernel.org/r/20200414150233.24495-7-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/readahead.c b/mm/readahead.c
index 9fcd4e32b62da792e99ebaa0856ae18439b39f68..9d9aa4ffc7d4c7acfcd22eead24a89668b474385 100644 (file)
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -113,29 +113,32 @@ int read_cache_pages(struct address_space *mapping, struct list_head *pages,
 
 EXPORT_SYMBOL(read_cache_pages);
 
-static void read_pages(struct address_space *mapping, struct file *filp,
-               struct list_head *pages, unsigned int nr_pages, gfp_t gfp)
+static void read_pages(struct readahead_control *rac, struct list_head *pages,
+               gfp_t gfp)
 {
+       const struct address_space_operations *aops = rac->mapping->a_ops;
        struct blk_plug plug;
        unsigned page_idx;
 
-       if (!nr_pages)
+       if (!readahead_count(rac))
                return;
 
        blk_start_plug(&plug);
 
-       if (mapping->a_ops->readpages) {
-               mapping->a_ops->readpages(filp, mapping, pages, nr_pages);
+       if (aops->readpages) {
+               aops->readpages(rac->file, rac->mapping, pages,
+                               readahead_count(rac));
                /* Clean up the remaining pages */
                put_pages_list(pages);
                goto out;
        }
 
-       for (page_idx = 0; page_idx < nr_pages; page_idx++) {
+       for (page_idx = 0; page_idx < readahead_count(rac); page_idx++) {
                struct page *page = lru_to_page(pages);
                list_del(&page->lru);
-               if (!add_to_page_cache_lru(page, mapping, page->index, gfp))
-                       mapping->a_ops->readpage(filp, page);
+               if (!add_to_page_cache_lru(page, rac->mapping, page->index,
+                               gfp))
+                       aops->readpage(rac->file, page);
                put_page(page);
        }
 
@@ -143,6 +146,7 @@ out:
        blk_finish_plug(&plug);
 
        BUG_ON(!list_empty(pages));
+       rac->_nr_pages = 0;
 }
 
 /*
@@ -160,9 +164,12 @@ void __do_page_cache_readahead(struct address_space *mapping,
        unsigned long end_index;        /* The last page we want to read */
        LIST_HEAD(page_pool);
        int page_idx;
-       unsigned int nr_pages = 0;
        loff_t isize = i_size_read(inode);
        gfp_t gfp_mask = readahead_gfp_mask(mapping);
+       struct readahead_control rac = {
+               .mapping = mapping,
+               .file = filp,
+       };
 
        if (isize == 0)
                return;
@@ -185,9 +192,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
                         * contiguous pages before continuing with the next
                         * batch.
                         */
-                       read_pages(mapping, filp, &page_pool, nr_pages,
-                                               gfp_mask);
-                       nr_pages = 0;
+                       read_pages(&rac, &page_pool, gfp_mask);
                        continue;
                }
 
@@ -198,7 +203,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
                list_add(&page->lru, &page_pool);
                if (page_idx == nr_to_read - lookahead_size)
                        SetPageReadahead(page);
-               nr_pages++;
+               rac._nr_pages++;
        }
 
        /*
@@ -206,7 +211,7 @@ void __do_page_cache_readahead(struct address_space *mapping,
         * uptodate then the caller will launch readpage again, and
         * will then handle the error.
         */
-       read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask);
+       read_pages(&rac, &page_pool, gfp_mask);
 }
 
 /*