[PATCH v2 0/3] f2fs: support passing down write hints to block layer

[Hyunchul Lee <hyc.lee@gmail.com>]

From: Hyunchul Lee <cheol.lee@lge.com>

Changes since version 1:
 - Set 'whint_mode' to off if 'active_logs' is two or four 
 - Minor fixes suggested by Chao

This set implements passing down write hints to block layer with the
following mapping. This mapping equals the conclusion from discussion in
the link, https://sourceforge.net/p/linux-f2fs/mailman/message/36170969/

But there are two exceptions. (1) the 'iohint_mode' mount option is changed
to 'whint_mode'. (2) in "user-based" mode, WRITE_LIFE_EXTREME is passed
down instead of WRITE_LIFE_NOT_SET for files flagged with ioctl(COLD) and 
extension list.

1) whint_mode=off. F2FS only passes down WRITE_LIFE_NOT_SET.

2) whint_mode=user-based. F2FS tries to pass down hints given by
users.

User                  F2FS                     Block
----                  ----                     -----
                      META                     WRITE_LIFE_NOT_SET
                      HOT_NODE                 "
                      WARM_NODE                "
                      COLD_NODE                "
*ioctl(COLD)           COLD_DATA                WRITE_LIFE_EXTREME
*extension list        "                        "

-- buffered io
WRITE_LIFE_EXTREME    COLD_DATA                WRITE_LIFE_EXTREME
WRITE_LIFE_SHORT      HOT_DATA                 WRITE_LIFE_SHORT
WRITE_LIFE_NOT_SET    WARM_DATA                WRITE_LIFE_NOT_SET
WRITE_LIFE_NONE       "                        "
WRITE_LIFE_MEDIUM     "                        "
WRITE_LIFE_LONG       "                        "

-- direct io
WRITE_LIFE_EXTREME    COLD_DATA                WRITE_LIFE_EXTREME
WRITE_LIFE_SHORT      HOT_DATA                 WRITE_LIFE_SHORT
WRITE_LIFE_NOT_SET    WARM_DATA                WRITE_LIFE_NOT_SET
WRITE_LIFE_NONE       "                        WRITE_LIFE_NONE
WRITE_LIFE_MEDIUM     "                        WRITE_LIFE_MEDIUM
WRITE_LIFE_LONG       "                        WRITE_LIFE_LONG

3) whint_mode=fs-based. F2FS passes down hints with its policy.

User                  F2FS                     Block
----                  ----                     -----
                      META                     WRITE_LIFE_MEDIUM;
                      HOT_NODE                 WRITE_LIFE_NOT_SET
                      WARM_NODE                "
                      COLD_NODE                WRITE_LIFE_NONE
ioctl(COLD)           COLD_DATA                WRITE_LIFE_EXTREME
extension list        "                        "

-- buffered io
WRITE_LIFE_EXTREME    COLD_DATA                WRITE_LIFE_EXTREME
WRITE_LIFE_SHORT      HOT_DATA                 WRITE_LIFE_SHORT
WRITE_LIFE_NOT_SET    WARM_DATA                WRITE_LIFE_LONG
WRITE_LIFE_NONE       "                        "
WRITE_LIFE_MEDIUM     "                        "
WRITE_LIFE_LONG       "                        "

-- direct io
WRITE_LIFE_EXTREME    COLD_DATA                WRITE_LIFE_EXTREME
WRITE_LIFE_SHORT      HOT_DATA                 WRITE_LIFE_SHORT
WRITE_LIFE_NOT_SET    WARM_DATA                WRITE_LIFE_NOT_SET
WRITE_LIFE_NONE       "                        WRITE_LIFE_NONE
WRITE_LIFE_MEDIUM     "                        WRITE_LIFE_MEDIUM
WRITE_LIFE_LONG       "                        WRITE_LIFE_LONG

Hyunchul Lee (3):
  f2fs: support passing down write hints given by users to block layer
  f2fs: support passing down write hints to block layer with F2FS policy
  f2fs: Add the 'whint_mode' mount option to f2fs documentation

 Documentation/filesystems/f2fs.txt |  6 +++
 fs/f2fs/data.c                     | 28 +++++++++--
 fs/f2fs/f2fs.h                     | 10 ++++
 fs/f2fs/segment.c                  | 98 ++++++++++++++++++++++++++++++++++++++
 fs/f2fs/super.c                    | 35 +++++++++++++-
 5 files changed, 171 insertions(+), 6 deletions(-)

-- 
1.9.1