ceph: make readpages fully async

When we get a ->readpages() aop, submit async reads for all page ranges
in the provided page list.  Lock the pages immediately, so that VFS/MM
will block until the reads complete.
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/addr.c

@@ -228,102 +228,147 @@ static int ceph_readpage(struct file *filp, struct page *page)
 }
 
 /*
- * Build a vector of contiguous pages from the provided page list.
+ * Finish an async read(ahead) op.
  */
-static struct page **page_vector_from_list(struct list_head *page_list,
-					   unsigned *nr_pages)
+static void finish_read(struct ceph_osd_request *req, struct ceph_msg *msg)
 {
-	struct page **pages;
-	struct page *page;
-	int next_index, contig_pages = 0;
+	struct inode *inode = req->r_inode;
+	struct ceph_osd_reply_head *replyhead;
+	int rc, bytes;
+	int i;
 
-	/* build page vector */
-	pages = kmalloc(sizeof(*pages) * *nr_pages, GFP_NOFS);
-	if (!pages)
-		return ERR_PTR(-ENOMEM);
+	/* parse reply */
+	replyhead = msg->front.iov_base;
+	WARN_ON(le32_to_cpu(replyhead->num_ops) == 0);
+	rc = le32_to_cpu(replyhead->result);
+	bytes = le32_to_cpu(msg->hdr.data_len);
 
-	BUG_ON(list_empty(page_list));
-	next_index = list_entry(page_list->prev, struct page, lru)->index;
-	list_for_each_entry_reverse(page, page_list, lru) {
-		if (page->index == next_index) {
-			dout("readpages page %d %p\n", contig_pages, page);
-			pages[contig_pages] = page;
-			contig_pages++;
-			next_index++;
-		} else {
-			break;
+	dout("finish_read %p req %p rc %d bytes %d\n", inode, req, rc, bytes);
+
+	/* unlock all pages, zeroing any data we didn't read */
+	for (i = 0; i < req->r_num_pages; i++, bytes -= PAGE_CACHE_SIZE) {
+		struct page *page = req->r_pages[i];
+
+		if (bytes < (int)PAGE_CACHE_SIZE) {
+			/* zero (remainder of) page */
+			int s = bytes < 0 ? 0 : bytes;
+			zero_user_segment(page, s, PAGE_CACHE_SIZE);
 		}
+ 		dout("finish_read %p uptodate %p idx %lu\n", inode, page,
+		     page->index);
+		flush_dcache_page(page);
+		SetPageUptodate(page);
+		unlock_page(page);
+		page_cache_release(page);
 	}
-	*nr_pages = contig_pages;
-	return pages;
+	kfree(req->r_pages);
 }
 
 /*
- * Read multiple pages.  Leave pages we don't read + unlock in page_list;
- * the caller (VM) cleans them up.
+ * start an async read(ahead) operation.  return nr_pages we submitted
+ * a read for on success, or negative error code.
  */
-static int ceph_readpages(struct file *file, struct address_space *mapping,
-			  struct list_head *page_list, unsigned nr_pages)
+static int start_read(struct inode *inode, struct list_head *page_list)
 {
-	struct inode *inode = file->f_dentry->d_inode;
-	struct ceph_inode_info *ci = ceph_inode(inode);
 	struct ceph_osd_client *osdc =
 		&ceph_inode_to_client(inode)->client->osdc;
-	int rc = 0;
-	struct page **pages;
-	loff_t offset;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct page *page = list_entry(page_list->prev, struct page, lru);
+	struct ceph_osd_request *req;
+	u64 off;
 	u64 len;
+	int i;
+	struct page **pages;
+	pgoff_t next_index;
+	int nr_pages = 0;
+	int ret;
 
-	dout("readpages %p file %p nr_pages %d\n",
-	     inode, file, nr_pages);
-
-	pages = page_vector_from_list(page_list, &nr_pages);
-	if (IS_ERR(pages))
-		return PTR_ERR(pages);
+	off = page->index << PAGE_CACHE_SHIFT;
 
-	/* guess read extent */
-	offset = pages[0]->index << PAGE_CACHE_SHIFT;
+	/* count pages */
+	next_index = page->index;
+	list_for_each_entry_reverse(page, page_list, lru) {
+		if (page->index != next_index)
+			break;
+		nr_pages++;
+		next_index++;
+	}
 	len = nr_pages << PAGE_CACHE_SHIFT;
-	rc = ceph_osdc_readpages(osdc, ceph_vino(inode), &ci->i_layout,
-				 offset, &len,
-				 ci->i_truncate_seq, ci->i_truncate_size,
-				 pages, nr_pages, 0);
-	if (rc == -ENOENT)
-		rc = 0;
-	if (rc < 0)
-		goto out;
-
-	for (; !list_empty(page_list) && len > 0;
-	     rc -= PAGE_CACHE_SIZE, len -= PAGE_CACHE_SIZE) {
-		struct page *page =
-			list_entry(page_list->prev, struct page, lru);
+	dout("start_read %p nr_pages %d is %lld~%lld\n", inode, nr_pages,
+	     off, len);
+
+	req = ceph_osdc_new_request(osdc, &ci->i_layout, ceph_vino(inode),
+				    off, &len,
+				    CEPH_OSD_OP_READ, CEPH_OSD_FLAG_READ,
+				    NULL, 0,
+				    ci->i_truncate_seq, ci->i_truncate_size,
+				    NULL, false, 1, 0);
+	if (!req)
+		return -ENOMEM;
 
+	/* build page vector */
+	nr_pages = len >> PAGE_CACHE_SHIFT;
+	pages = kmalloc(sizeof(*pages) * nr_pages, GFP_NOFS);
+	ret = -ENOMEM;
+	if (!pages)
+		goto out;
+	for (i = 0; i < nr_pages; ++i) {
+		page = list_entry(page_list->prev, struct page, lru);
+		BUG_ON(PageLocked(page));
 		list_del(&page->lru);
-
-		if (rc < (int)PAGE_CACHE_SIZE) {
-			/* zero (remainder of) page */
-			int s = rc < 0 ? 0 : rc;
-			zero_user_segment(page, s, PAGE_CACHE_SIZE);
-		}
-
-		if (add_to_page_cache_lru(page, mapping, page->index,
+		
+ 		dout("start_read %p adding %p idx %lu\n", inode, page,
+		     page->index);
+		if (add_to_page_cache_lru(page, &inode->i_data, page->index,
 					  GFP_NOFS)) {
 			page_cache_release(page);
-			dout("readpages %p add_to_page_cache failed %p\n",
+			dout("start_read %p add_to_page_cache failed %p\n",
 			     inode, page);
-			continue;
+			nr_pages = i;
+			goto out_pages;
 		}
-		dout("readpages %p adding %p idx %lu\n", inode, page,
-		     page->index);
-		flush_dcache_page(page);
-		SetPageUptodate(page);
-		unlock_page(page);
-		page_cache_release(page);
+		pages[i] = page;
 	}
-	rc = 0;
+	req->r_pages = pages;
+	req->r_num_pages = nr_pages;
+	req->r_callback = finish_read;
+	req->r_inode = inode;
+
+	dout("start_read %p starting %p %lld~%lld\n", inode, req, off, len);
+	ret = ceph_osdc_start_request(osdc, req, false);
+	if (ret < 0)
+		goto out_pages;
+	ceph_osdc_put_request(req);
+	return nr_pages;
 
-out:
+out_pages:
+	ceph_release_page_vector(pages, nr_pages);
 	kfree(pages);
+out:
+	ceph_osdc_put_request(req);
+	return ret;
+}
+
+
+/*
+ * Read multiple pages.  Leave pages we don't read + unlock in page_list;
+ * the caller (VM) cleans them up.
+ */
+static int ceph_readpages(struct file *file, struct address_space *mapping,
+			  struct list_head *page_list, unsigned nr_pages)
+{
+	struct inode *inode = file->f_dentry->d_inode;
+	int rc = 0;
+
+	dout("readpages %p file %p nr_pages %d\n", inode, file, nr_pages);
+	while (!list_empty(page_list)) {
+		rc = start_read(inode, page_list);
+		if (rc < 0)
+			goto out;
+		BUG_ON(rc == 0);
+	}
+out:
+	dout("readpages %p file %p ret %d\n", inode, file, rc);
 	return rc;
 }