For Subject: s/readpage/readpages/

On Mon, Jan 25, 2021 at 09:37:29PM +0000, David Howells wrote:

+int __nfs_readahead_from_fscache(struct nfs_readdesc *desc,
+				 struct readahead_control *rac)

I thought you wanted it called ractl instead of rac?  That's what I've
been using in new code.

-	dfprintk(FSCACHE, "NFS: nfs_getpages_from_fscache (0x%p/%u/0x%p)\n",
-		 nfs_i_fscache(inode), npages, inode);
+	dfprintk(FSCACHE, "NFS: nfs_readahead_from_fscache (0x%p/0x%p)\n",
+		 nfs_i_fscache(inode), inode);

We do have readahead_count() if this is useful information to be logging.

+static inline int nfs_readahead_from_fscache(struct nfs_readdesc *desc,
+					     struct readahead_control *rac)
 {
-	if (NFS_I(inode)->fscache)
-		return __nfs_readpages_from_fscache(ctx, inode, mapping, pages,
-						    nr_pages);
+	if (NFS_I(rac->mapping->host)->fscache)
+		return __nfs_readahead_from_fscache(desc, rac);
 	return -ENOBUFS;
 }

Not entirely sure that it's worth having the two functions separated any more.

 	/* attempt to read as many of the pages as possible from the cache
 	 * - this returns -ENOBUFS immediately if the cookie is negative
 	 */
-	ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
-					 pages, &nr_pages);
+	ret = nfs_readahead_from_fscache(&desc, rac);
 	if (ret == 0)
 		goto read_complete; /* all pages were read */
 
 	nfs_pageio_init_read(&desc.pgio, inode, false,
 			     &nfs_async_read_completion_ops);
 
-	ret = read_cache_pages(mapping, pages, readpage_async_filler, &desc);
+	while ((page = readahead_page(rac))) {
+		ret = readpage_async_filler(&desc, page);
+		put_page(page);
+	}

I thought with the new API we didn't need to do this kind of thing
any more?  ie no matter whether fscache is configured in or not, it'll
submit the I/Os.