Orangef: implement orangefs_readahead.

Also remove open-coded readahead logic from orangefs_readpage.
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

fs/orangefs/file.c

@@ -248,21 +248,7 @@ ssize_t wait_for_direct_io(enum ORANGEFS_io_type type, struct inode *inode,
 		 *       or it can pointers to struct page's
 		 */
 
-		/*
-		 * When reading, readahead_size will only be zero when
-		 * we're doing O_DIRECT, otherwise we got here from
-		 * orangefs_readpage.
-		 *
-		 * If we got here from orangefs_readpage we want to
-		 * copy either a page or the whole file into the io
-		 * vector, whichever is smaller.
-		 */
-		if (readahead_size)
-			copy_amount =
-				min(new_op->downcall.resp.io.amt_complete,
-					(__s64)PAGE_SIZE);
-		else
-			copy_amount = new_op->downcall.resp.io.amt_complete;
+		copy_amount = new_op->downcall.resp.io.amt_complete;
 
 		ret = orangefs_bufmap_copy_to_iovec(iter, buffer_index,
 			copy_amount);
@@ -283,19 +269,11 @@ ssize_t wait_for_direct_io(enum ORANGEFS_io_type type, struct inode *inode,
 
 out:
 	if (buffer_index >= 0) {
-		if ((readahead_size) && (type == ORANGEFS_IO_READ)) {
-			/* readpage */
-			*index_return = buffer_index;
-			gossip_debug(GOSSIP_FILE_DEBUG,
-				"%s: hold on to buffer_index :%d:\n",
-				__func__, buffer_index);
-		} else {
-			/* O_DIRECT */
-			orangefs_bufmap_put(buffer_index);
-			gossip_debug(GOSSIP_FILE_DEBUG,
-				"%s(%pU): PUT buffer_index %d\n",
-				__func__, handle, buffer_index);
-		}
+		orangefs_bufmap_put(buffer_index);
+		gossip_debug(GOSSIP_FILE_DEBUG,
+			"%s(%pU): PUT buffer_index %d\n",
+			__func__, handle, buffer_index);
+		buffer_index = -1;
 	}
 	op_release(new_op);
 	return ret;

fs/orangefs/inode.c

@@ -245,6 +245,50 @@ static int orangefs_writepages(struct address_space *mapping,
 
 static int orangefs_launder_page(struct page *);
 
+static void orangefs_readahead(struct readahead_control *rac)
+{
+	loff_t offset;
+	struct iov_iter iter;
+	struct file *file = rac->file;
+	struct inode *inode = file->f_mapping->host;
+	struct xarray *i_pages;
+	struct page *page;
+	loff_t new_start = readahead_pos(rac);
+	int ret;
+	size_t new_len = 0;
+
+	loff_t bytes_remaining = inode->i_size - readahead_pos(rac);
+	loff_t pages_remaining = bytes_remaining / PAGE_SIZE;
+
+	if (pages_remaining >= 1024)
+		new_len = 4194304;
+	else if (pages_remaining > readahead_count(rac))
+		new_len = bytes_remaining;
+
+	if (new_len)
+		readahead_expand(rac, new_start, new_len);
+
+	offset = readahead_pos(rac);
+	i_pages = &file->f_mapping->i_pages;
+
+	iov_iter_xarray(&iter, READ, i_pages, offset, readahead_length(rac));
+
+	/* read in the pages. */
+	if ((ret = wait_for_direct_io(ORANGEFS_IO_READ, inode,
+			&offset, &iter, readahead_length(rac),
+			inode->i_size, NULL, NULL, file)) < 0)
+		gossip_debug(GOSSIP_FILE_DEBUG,
+			"%s: wait_for_direct_io failed. \n", __func__);
+	else
+		ret = 0;
+
+	/* clean up. */
+	while ((page = readahead_page(rac))) {
+		page_endio(page, false, ret);
+		put_page(page);
+	}
+}
+
 static int orangefs_readpage(struct file *file, struct page *page)
 {
 	struct inode *inode = page->mapping->host;
@@ -252,44 +296,24 @@ static int orangefs_readpage(struct file *file, struct page *page)
 	struct bio_vec bv;
 	ssize_t ret;
 	loff_t off; /* offset into this page */
-	pgoff_t index; /* which page */
-	struct page *next_page;
-	char *kaddr;
-	loff_t read_size;
-	int buffer_index = -1; /* orangefs shared memory slot */
-	int slot_index;   /* index into slot */
-	int remaining;
-
-	/*
-	 * Get up to this many bytes from Orangefs at a time and try
-	 * to fill them into the page cache at once. Tests with dd made
-	 * this seem like a reasonable static number, if there was
-	 * interest perhaps this number could be made setable through
-	 * sysfs...
-	 */
-	read_size = 524288;
 
 	if (PageDirty(page))
 		orangefs_launder_page(page);
 
 	off = page_offset(page);
-	index = off >> PAGE_SHIFT;
 	bv.bv_page = page;
 	bv.bv_len = PAGE_SIZE;
 	bv.bv_offset = 0;
 	iov_iter_bvec(&iter, READ, &bv, 1, PAGE_SIZE);
 
 	ret = wait_for_direct_io(ORANGEFS_IO_READ, inode, &off, &iter,
-	    read_size, inode->i_size, NULL, &buffer_index, file);
-	remaining = ret;
+	    PAGE_SIZE, inode->i_size, NULL, NULL, file);
 	/* this will only zero remaining unread portions of the page data */
 	iov_iter_zero(~0U, &iter);
 	/* takes care of potential aliasing */
 	flush_dcache_page(page);
 	if (ret < 0) {
 		SetPageError(page);
-		unlock_page(page);
-		goto out;
 	} else {
 		SetPageUptodate(page);
 		if (PageError(page))
@@ -298,60 +322,7 @@ static int orangefs_readpage(struct file *file, struct page *page)
 	}
 	/* unlock the page after the ->readpage() routine completes */
 	unlock_page(page);
-
-	if (remaining > PAGE_SIZE) {
-		slot_index = 0;
-		while ((remaining - PAGE_SIZE) >= PAGE_SIZE) {
-			remaining -= PAGE_SIZE;
-			/*
-			 * It is an optimization to try and fill more than one
-			 * page... by now we've already gotten the single
-			 * page we were after, if stuff doesn't seem to
-			 * be going our way at this point just return
-			 * and hope for the best.
-			 *
-			 * If we look for pages and they're already there is
-			 * one reason to give up, and if they're not there
-			 * and we can't create them is another reason.
-			 */
-
-			index++;
-			slot_index++;
-			next_page = find_get_page(inode->i_mapping, index);
-			if (next_page) {
-				gossip_debug(GOSSIP_FILE_DEBUG,
-					"%s: found next page, quitting\n",
-					__func__);
-				put_page(next_page);
-				goto out;
-			}
-			next_page = find_or_create_page(inode->i_mapping,
-							index,
-							GFP_KERNEL);
-			/*
-			 * I've never hit this, leave it as a printk for
-			 * now so it will be obvious.
-			 */
-			if (!next_page) {
-				printk("%s: can't create next page, quitting\n",
-					__func__);
-				goto out;
-			}
-			kaddr = kmap_atomic(next_page);
-			orangefs_bufmap_page_fill(kaddr,
-						buffer_index,
-						slot_index);
-			kunmap_atomic(kaddr);
-			SetPageUptodate(next_page);
-			unlock_page(next_page);
-			put_page(next_page);
-		}
-	}
-
-out:
-	if (buffer_index != -1)
-		orangefs_bufmap_put(buffer_index);
-	return ret;
+        return ret;
 }
 
 static int orangefs_write_begin(struct file *file,
@@ -660,6 +631,7 @@ static ssize_t orangefs_direct_IO(struct kiocb *iocb,
 /** ORANGEFS2 implementation of address space operations */
 static const struct address_space_operations orangefs_address_operations = {
 	.writepage = orangefs_writepage,
+	.readahead = orangefs_readahead,
 	.readpage = orangefs_readpage,
 	.writepages = orangefs_writepages,
 	.set_page_dirty = __set_page_dirty_nobuffers,