Due to the previous discussion[1], I learned that you people have discussed this system call a few times (but not conclusion) and it can solve my problem about pagecache scanning (see[2] for my motivation.) So I try it now. The main patch of this patchset is patch 2, and this is based on Johannes's previous version[3], so I CCed people who joined that discussion. While there might be controversies about the format of data copied from kernel to userspace, I take the Kirill's suggestion[4] which uses a flag to choose the data format, which is extensible and flexible (you can cut off some info if you don't need it.) And I added simple tests at patch 3, and patch 2 passes all the tests. Any comments are welcomed. [1] http://marc.info/?l=linux-kernel&m=140072606903894&w=2 [2] http://marc.info/?l=linux-mm&m=140072522603776&w=2 [3] http://thread.gmane.org/gmane.linux.kernel/1439212/focus=1441919 [4] http://marc.info/?l=linux-kernel&m=140075509611532&w=2 Thanks, Naoya Horiguchi --- Summary: Naoya Horiguchi (3): replace PAGECACHE_TAG_* definition with enumeration mm: introduce fincore() selftest: add test code for fincore() arch/x86/syscalls/syscall_64.tbl | 1 + include/linux/fs.h | 9 +- include/linux/syscalls.h | 2 + mm/Makefile | 2 +- mm/fincore.c | 362 +++++++++++++++++++++ tools/testing/selftests/Makefile | 1 + tools/testing/selftests/fincore/Makefile | 31 ++ .../selftests/fincore/create_hugetlbfs_file.c | 49 +++ tools/testing/selftests/fincore/fincore.c | 153 +++++++++ tools/testing/selftests/fincore/run_fincoretests | 355 ++++++++++++++++++++ 10 files changed, 961 insertions(+), 4 deletions(-) -- 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>