On Fri, 27 Mar 2015 09:30:46 -0700 Andrew Morton [off-list ref] wrote:

I expect that this situation (first part in cache, latter part not in
cache) is rare - for reasonably small requests the common cases will be
"all cached" and "nothing cached".  So perhaps the best approach here
is for samba to add special handling for the short read, to work out
the reason for its occurrence.

Alternatively we could add another flag to pread2() to select this
"throw away my data and return -EAGAIN" behaviour.  Presumably
implemented with an i_size check, but it's gonna be racy.

Here's a better way:

	nr_read = pread2(buf, len);
	if (nr_read < len)
		nr_read += pread(buf + nr_read, len - nr_read);
	if (nr_read < len)
		we_hit_eof();