btrfs: add a btrfs_dio_rw wrapper

Add a wrapper around iomap_dio_rw that keeps the direct I/O internals
isolated in inode.c.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -3359,9 +3359,9 @@ ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter,
 ssize_t btrfs_do_encoded_write(struct kiocb *iocb, struct iov_iter *from,
 			     const struct btrfs_ioctl_encoded_io_args *encoded);
 
+ssize_t btrfs_dio_rw(struct kiocb *iocb, struct iov_iter *iter, size_t done_before);
+
 extern const struct dentry_operations btrfs_dentry_operations;
-extern const struct iomap_ops btrfs_dio_iomap_ops;
-extern const struct iomap_dio_ops btrfs_dio_ops;
 
 /* Inode locking type flags, by default the exclusive lock is taken */
 #define BTRFS_ILOCK_SHARED	(1U << 0)

fs/btrfs/file.c

@@ -1929,8 +1929,7 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
 	 */
 again:
 	from->nofault = true;
-	err = iomap_dio_rw(iocb, from, &btrfs_dio_iomap_ops, &btrfs_dio_ops,
-			   IOMAP_DIO_PARTIAL, written);
+	err = btrfs_dio_rw(iocb, from, written);
 	from->nofault = false;
 
 	/* No increment (+=) because iomap returns a cumulative value. */
@@ -3693,8 +3692,7 @@ static ssize_t btrfs_direct_read(struct kiocb *iocb, struct iov_iter *to)
 	 */
 	pagefault_disable();
 	to->nofault = true;
-	ret = iomap_dio_rw(iocb, to, &btrfs_dio_iomap_ops, &btrfs_dio_ops,
-			   IOMAP_DIO_PARTIAL, read);
+	ret = btrfs_dio_rw(iocb, to, read);
 	to->nofault = false;
 	pagefault_enable();
 

fs/btrfs/inode.c

@@ -8155,15 +8155,21 @@ static void btrfs_submit_direct(const struct iomap_iter *iter,
 	btrfs_dio_private_put(dip);
 }
 
-const struct iomap_ops btrfs_dio_iomap_ops = {
+static const struct iomap_ops btrfs_dio_iomap_ops = {
 	.iomap_begin            = btrfs_dio_iomap_begin,
 	.iomap_end              = btrfs_dio_iomap_end,
 };
 
-const struct iomap_dio_ops btrfs_dio_ops = {
+static const struct iomap_dio_ops btrfs_dio_ops = {
 	.submit_io		= btrfs_submit_direct,
 };
 
+ssize_t btrfs_dio_rw(struct kiocb *iocb, struct iov_iter *iter, size_t done_before)
+{
+	return iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops, &btrfs_dio_ops,
+			    IOMAP_DIO_PARTIAL, done_before);
+}
+
 static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 			u64 start, u64 len)
 {