[RFC][PATCH 0/3] mm: introduce fincore()

[Naoya Horiguchi]

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(-)
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