From 5d5e9f1462e882b5dfe44711f9895a08493e9ea9 Mon Sep 17 00:00:00 2001
From: Erez Zadok <ezk@cs.sunysb.edu>
Date: Mon, 11 Aug 2014 22:10:28 -0400
Subject: [PATCH] Unionfs: support asynchronous-IO (AIO) operations

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Mengyang Li <li.mengyang@stonybrook.edu>
---
 fs/unionfs/file.c  | 85 ++++++++++++++++++++++++++++++++++++++++++++++
 fs/unionfs/union.h |  1 +
 2 files changed, 86 insertions(+)

diff --git a/fs/unionfs/file.c b/fs/unionfs/file.c
index 2f0aa62379a..d4dc7ba3ec7 100644
--- a/fs/unionfs/file.c
+++ b/fs/unionfs/file.c
@@ -85,6 +85,89 @@ out:
 	return err;
 }
 
+static ssize_t unionfs_aio_read(struct kiocb *iocb, const struct iovec
+				*iov, unsigned long nr_segs, loff_t pos)
+{
+	int err = -EINVAL;
+	struct file *file = iocb->ki_filp, *lower_file;
+	struct dentry *dentry = file->f_path.dentry;
+	struct dentry *parent;
+
+	unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+	parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+	unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+	err = unionfs_file_revalidate(file, parent, true);
+	if (unlikely(err))
+		goto out;
+
+	lower_file = unionfs_lower_file(file);
+	if (!lower_file->f_op->aio_read)
+		goto out;
+
+	get_file(lower_file);
+	iocb->ki_filp = lower_file;
+	err = lower_file->f_op->aio_read(iocb, iov, nr_segs, pos);
+	iocb->ki_filp = file;
+	fput(lower_file);
+
+	/* update our inode atime upon a successful lower read */
+	/* XXX: need to update upper inode atime when AIO completes */
+	if (err >= 0) {
+		fsstack_copy_attr_atime(dentry->d_inode,
+					lower_file->f_path.dentry->d_inode);
+		unionfs_check_file(file);
+	}
+out:
+	unionfs_unlock_dentry(dentry);
+	unionfs_unlock_parent(dentry, parent);
+	unionfs_read_unlock(dentry->d_sb);
+	return err;
+}
+
+static ssize_t unionfs_aio_write(struct kiocb *iocb, const struct iovec
+		*iov, unsigned long nr_segs, loff_t pos)
+{
+	int err = -EINVAL;
+	struct file *file = iocb->ki_filp, *lower_file;
+	struct dentry *dentry = file->f_path.dentry;
+	struct dentry *parent;
+
+	unionfs_read_lock(dentry->d_sb, UNIONFS_SMUTEX_PARENT);
+	parent = unionfs_lock_parent(dentry, UNIONFS_DMUTEX_PARENT);
+	unionfs_lock_dentry(dentry, UNIONFS_DMUTEX_CHILD);
+
+	err = unionfs_file_revalidate(file, parent, true);
+	if (unlikely(err))
+		goto out;
+
+	lower_file = unionfs_lower_file(file);
+	if (!lower_file->f_op->aio_write)
+		goto out;
+
+	get_file(lower_file);
+	iocb->ki_filp = lower_file;
+	err = lower_file->f_op->aio_write(iocb, iov, nr_segs, pos);
+	iocb->ki_filp = file;
+	fput(lower_file);
+
+	/* update our inode times+sizes upon a successful lower write */
+	/* XXX: need to update upper inode times/sizes when AIO completes */
+	if (err >= 0) {
+		fsstack_copy_inode_size(dentry->d_inode,
+					lower_file->f_path.dentry->d_inode);
+		fsstack_copy_attr_times(dentry->d_inode,
+					lower_file->f_path.dentry->d_inode);
+		UNIONFS_F(file)->wrote_to_file = true; /* for delayed copyup */
+		unionfs_check_file(file);
+	}
+out:
+	unionfs_unlock_dentry(dentry);
+	unionfs_unlock_parent(dentry, parent);
+	unionfs_read_unlock(dentry->d_sb);
+	return err;
+}
+
 static int unionfs_file_readdir(struct file *file, void *dirent,
 				filldir_t filldir)
 {
@@ -366,6 +449,8 @@ struct file_operations unionfs_main_fops = {
 	.llseek		= generic_file_llseek,
 	.read		= unionfs_read,
 	.write		= unionfs_write,
+	.aio_read	= unionfs_aio_read,
+	.aio_write	= unionfs_aio_write,
 	.readdir	= unionfs_file_readdir,
 	.unlocked_ioctl	= unionfs_ioctl,
 #ifdef CONFIG_COMPAT
diff --git a/fs/unionfs/union.h b/fs/unionfs/union.h
index dc60b5d5316..6fc431b0525 100644
--- a/fs/unionfs/union.h
+++ b/fs/unionfs/union.h
@@ -22,6 +22,7 @@
 #include <linux/file.h>
 #include <linux/list.h>
 #include <linux/fs.h>
+#include <linux/aio.h>
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/mount.h>
-- 
2.34.1