btrfs: switch to ->write_iter()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/btrfs/file.c

@@ -447,7 +447,7 @@ static noinline int btrfs_copy_from_user(loff_t pos, int num_pages,
 		write_bytes -= copied;
 		total_copied += copied;
 
-		/* Return to btrfs_file_aio_write to fault page */
+		/* Return to btrfs_file_write_iter to fault page */
 		if (unlikely(copied == 0))
 			break;
 
@@ -1708,9 +1708,8 @@ static void update_time_for_write(struct inode *inode)
 		inode_inc_iversion(inode);
 }
 
-static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
-				    const struct iovec *iov,
-				    unsigned long nr_segs, loff_t pos)
+static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
+				    struct iov_iter *from)
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file_inode(file);
@@ -1719,15 +1718,12 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
 	u64 end_pos;
 	ssize_t num_written = 0;
 	ssize_t err = 0;
-	size_t count;
+	size_t count = iov_iter_count(from);
 	bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);
-	struct iov_iter i;
+	loff_t pos = iocb->ki_pos;
 
 	mutex_lock(&inode->i_mutex);
 
-	count = iov_length(iov, nr_segs);
-	iov_iter_init(&i, WRITE, iov, nr_segs, count);
-
 	current->backing_dev_info = inode->i_mapping->backing_dev_info;
 	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
 	if (err) {
@@ -1740,7 +1736,7 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
 		goto out;
 	}
 
-	iov_iter_truncate(&i, count);
+	iov_iter_truncate(from, count);
 
 	err = file_remove_suid(file);
 	if (err) {
@@ -1783,9 +1779,9 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
 		atomic_inc(&BTRFS_I(inode)->sync_writers);
 
 	if (unlikely(file->f_flags & O_DIRECT)) {
-		num_written = __btrfs_direct_write(iocb, &i, pos);
+		num_written = __btrfs_direct_write(iocb, from, pos);
 	} else {
-		num_written = __btrfs_buffered_write(file, &i, pos);
+		num_written = __btrfs_buffered_write(file, from, pos);
 		if (num_written > 0)
 			iocb->ki_pos = pos + num_written;
 	}
@@ -2623,10 +2619,10 @@ out:
 const struct file_operations btrfs_file_operations = {
 	.llseek		= btrfs_file_llseek,
 	.read		= new_sync_read,
-	.write		= do_sync_write,
+	.write		= new_sync_write,
 	.read_iter      = generic_file_read_iter,
 	.splice_read	= generic_file_splice_read,
-	.aio_write	= btrfs_file_aio_write,
+	.write_iter	= btrfs_file_write_iter,
 	.mmap		= btrfs_file_mmap,
 	.open		= generic_file_open,
 	.release	= btrfs_release_file,