Don't use atomic kmap for mapping userspace buffers in device
read/write/splice.
This is necessary because the next patch (adding store notify)
requires that caller of fuse_copy_page() may sleep between
invocations. The simplest way to ensure this is to change the atomic
kmaps to non-atomic ones.
Thankfully architectures where kmap() is not a no-op are going out of
fashion, so we can ignore the (probably negligible) performance impact
of this change.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
7909b1c640