On Wed, Oct 31, 2012 at 2:24 AM, <chrubis@xxxxxxx> wrote: > Hi! > I'm currently revisiting mmap related tests in LTP (Linux Test Project) > and I've came to the tests testing that writes to the partially > mapped page (at the end of mapping) are carried out correctly. > > These tests fails because even after the object is unmapped and the > file-descriptor closed the pages still stays in the page cache so if > (possibly another process) opens and maps the file again the whole > content of the partial page is preserved. > > Strictly speaking this is not a bug at least when sticking to regular > files as POSIX which says that the change is not written out. In this > case the file content is correct and forcing the data to be written out > by msync() makes the test pass. The SHM mappings seems to preserve the > content even after calling msync() which is, in my opinion, POSIX > violation although a minor one. > fsync implemented in SHM is noop_fsync. May be we should extend it if needed. > Looking at the test results I have, the file based mmap test worked fine > on 2.6.5 (or perhaps the page cache was working/setup differently and > the test succeeded by accidend). > > Attached is a stripped down LTP test for the problem, uncommenting the > msync() makes the test succeed. > > I would like to hear your opinions on this problems. > > -- > Cyril Hrubis > chrubis@xxxxxxx -- Regards, --Bob -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>