perf tools: Fine tune readn function
perf tools: Fine tune readn function

Added a 'left' variable to make the flow clearer, and added a debug
check for the return value - returning 'n' is more obvious.

Added small comment for readn.

Signed-off-by: Jiri Olsa <2c6594f608aa3d41e98d48846a6328831f7084ad@redhat.com>
Original-patch-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@kernel.org>
Cc: Adrian Hunter <41bb5944f244750b7cf0394140496972a3f1bee3@intel.com>
Cc: David Ahern <b80c1600f604d3b0d768f26f90a76757e76005dd@gmail.com>
Cc: Frederic Weisbecker <e8a1bf9163cb25e93cfd6540f223b3872ea7ee55@gmail.com>
Cc: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@kernel.org>
Cc: Mike Galbraith <3cfa3897b7f55b5396b7a47c83b66325184bc9b4@gmx.de>
Cc: Namhyung Kim <5c915a589b3ddf58cebf14bec41bcc143b37ac3c@kernel.org>
Cc: Peter Zijlstra <3fddac958924aef220f202ca567388ddab3f14a8@infradead.org>
Link: http://lkml.kernel.org/r/1385634619-8129-4-git-send-email-2c6594f608aa3d41e98d48846a6328831f7084ad@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <293abb6b76d7791c0732cc517d38c4b5c734b87f@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs