[PATCH v19 07/15] splice: Do splice read from a file without using ITER_PIPE

[David Howells <dhowells@redhat.com>]

Make generic_file_splice_read() use filemap_splice_read() and
direct_splice_read() rather than using an ITER_PIPE and call_read_iter().

With this, ITER_PIPE is no longer used.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
cc: Jens Axboe <axboe@kernel.dk>
cc: Steve French <smfrench@gmail.com>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: David Hildenbrand <david@redhat.com>
cc: John Hubbard <jhubbard@nvidia.com>
cc: linux-mm@kvack.org
cc: linux-block@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
---

Notes:
    ver #18)
     - Split out the change to cifs to make it use generic_file_splice_read().
     - Split out the unexport of filemap_splice_read() (still needed by cifs).

 fs/splice.c | 30 +++++++-----------------------
 1 file changed, 7 insertions(+), 23 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 90ccd3666dca..f46dd1fb367b 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -387,29 +387,13 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 				 struct pipe_inode_info *pipe, size_t len,
 				 unsigned int flags)
 {
-	struct iov_iter to;
-	struct kiocb kiocb;
-	int ret;
-
-	iov_iter_pipe(&to, ITER_DEST, pipe, len);
-	init_sync_kiocb(&kiocb, in);
-	kiocb.ki_pos = *ppos;
-	ret = call_read_iter(in, &kiocb, &to);
-	if (ret > 0) {
-		*ppos = kiocb.ki_pos;
-		file_accessed(in);
-	} else if (ret < 0) {
-		/* free what was emitted */
-		pipe_discard_from(pipe, to.start_head);
-		/*
-		 * callers of ->splice_read() expect -EAGAIN on
-		 * "can't put anything in there", rather than -EFAULT.
-		 */
-		if (ret == -EFAULT)
-			ret = -EAGAIN;
-	}
-
-	return ret;
+	if (unlikely(*ppos >= file_inode(in)->i_sb->s_maxbytes))
+		return 0;
+	if (unlikely(!len))
+		return 0;
+	if (in->f_flags & O_DIRECT)
+		return direct_splice_read(in, ppos, pipe, len, flags);
+	return filemap_splice_read(in, ppos, pipe, len, flags);
 }
 EXPORT_SYMBOL(generic_file_splice_read);