From 472479a68a357a8ff0deb56fd005fd1859c1b72a Mon Sep 17 00:00:00 2001
From: Jiufei Xue <jiufei.xue@linux.alibaba.com>
Date: Wed, 20 Nov 2019 17:45:25 +0800
Subject: [PATCH] BACKPORT: vfs: add vfs_iocb_iter_[read|write] helper
 functions

This doesn't cause any behavior changes and will be used by overlay async
IO implementation.

Remove 'kiocb_clone' from passthrough.c as this is the proper upstream
commit which adds the function.

Change-Id: Ic3d0ebd5cc2d945358f7295697ae02a829e2e919
Signed-off-by: Jiufei Xue <jiufei.xue@linux.alibaba.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/fuse/passthrough.c | 12 ----------
 fs/read_write.c       | 56 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h    | 16 +++++++++++++
 3 files changed, 72 insertions(+), 12 deletions(-)

diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c
index 013e2095ab9a..6031e72f3b5a 100644
--- a/fs/fuse/passthrough.c
+++ b/fs/fuse/passthrough.c
@@ -14,18 +14,6 @@ struct fuse_aio_req {
 	struct kiocb *iocb_fuse;
 };
 
-static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
-			       struct file *filp)
-{
-	*kiocb = (struct kiocb){
-		.ki_filp = filp,
-		.ki_flags = kiocb_src->ki_flags,
-		.ki_hint = kiocb_src->ki_hint,
-		.ki_ioprio = kiocb_src->ki_ioprio,
-		.ki_pos = kiocb_src->ki_pos,
-	};
-}
-
 static void fuse_file_accessed(struct file *dst_file, struct file *src_file)
 {
 	struct inode *dst_inode;
diff --git a/fs/read_write.c b/fs/read_write.c
index 93d06b4c5f78..301c4a4ba1d0 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -939,6 +939,34 @@ out:
 	return ret;
 }
 
+ssize_t vfs_iocb_iter_read(struct file *file, struct kiocb *iocb,
+			   struct iov_iter *iter)
+{
+	size_t tot_len;
+	ssize_t ret = 0;
+
+	if (!file->f_op->read_iter)
+		return -EINVAL;
+	if (!(file->f_mode & FMODE_READ))
+		return -EBADF;
+	if (!(file->f_mode & FMODE_CAN_READ))
+		return -EINVAL;
+
+	tot_len = iov_iter_count(iter);
+	if (!tot_len)
+		goto out;
+	ret = rw_verify_area(READ, file, &iocb->ki_pos, tot_len);
+	if (ret < 0)
+		return ret;
+
+	ret = call_read_iter(file, iocb, iter);
+out:
+	if (ret >= 0)
+		fsnotify_access(file);
+	return ret;
+}
+EXPORT_SYMBOL(vfs_iocb_iter_read);
+
 ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
 		rwf_t flags)
 {
@@ -975,6 +1003,34 @@ static ssize_t do_iter_write(struct file *file, struct iov_iter *iter,
 	return ret;
 }
 
+ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb,
+			    struct iov_iter *iter)
+{
+	size_t tot_len;
+	ssize_t ret = 0;
+
+	if (!file->f_op->write_iter)
+		return -EINVAL;
+	if (!(file->f_mode & FMODE_WRITE))
+		return -EBADF;
+	if (!(file->f_mode & FMODE_CAN_WRITE))
+		return -EINVAL;
+
+	tot_len = iov_iter_count(iter);
+	if (!tot_len)
+		return 0;
+	ret = rw_verify_area(WRITE, file, &iocb->ki_pos, tot_len);
+	if (ret < 0)
+		return ret;
+
+	ret = call_write_iter(file, iocb, iter);
+	if (ret > 0)
+		fsnotify_modify(file);
+
+	return ret;
+}
+EXPORT_SYMBOL(vfs_iocb_iter_write);
+
 ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,
 		rwf_t flags)
 {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 53be8d36da9c..e79b51ff5807 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2167,6 +2167,18 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 	};
 }
 
+static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
+			       struct file *filp)
+{
+	*kiocb = (struct kiocb) {
+		.ki_filp = filp,
+		.ki_flags = kiocb_src->ki_flags,
+		.ki_hint = kiocb_src->ki_hint,
+		.ki_ioprio = kiocb_src->ki_ioprio,
+		.ki_pos = kiocb_src->ki_pos,
+	};
+}
+
 /*
  * Inode state bits.  Protected by inode->i_lock
  *
@@ -3220,6 +3232,10 @@ ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
 		rwf_t flags);
 ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,
 		rwf_t flags);
+ssize_t vfs_iocb_iter_read(struct file *file, struct kiocb *iocb,
+			   struct iov_iter *iter);
+ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb,
+			    struct iov_iter *iter);
 
 /* fs/block_dev.c */
 extern ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to);