ocfs2: Provide a splice-read wrapper

ocfs2: Provide a splice-read wrapper

Provide a splice_read wrapper for ocfs2.  This emits trace lines and does
an atime lock/update before calling filemap_splice_read().  Splicing from
direct I/O is handled by the caller.

A couple of new tracepoints are added for this purpose.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
cc: Christoph Hellwig <hch@lst.de>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Mark Fasheh <mark@fasheh.com>
cc: Joel Becker <jlbec@evilplan.org>
cc: ocfs2-devel@oss.oracle.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-block@vger.kernel.org
cc: linux-mm@kvack.org
Link: https://lore.kernel.org/r/20230522135018.2742245-23-dhowells@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>