SERVER-7497 added the O_NOATIME flag to open() calls on Linux for files opened in read-only mode, but this generates errors for certain files:
http://buildlogs.mongodb.org/Linux%2064-bit%20DUR%20OFF/builds/1944/test/recent%20failures/sync2.js

Thu Dec 13 13:43:54.040 In File::open(), ::open for '/etc/lsb-release' failed with errno:1 Operation not permitted

The code should probably do what it did before, and only use O_NOATIME when opening files in read-write mode.