[PATCHSET v3 0/4] Submit ->readpages() IO as read-ahead

[Jens Axboe <axboe@kernel.dk>]

The only caller of ->readpages() is from read-ahead, yet we don't
submit IO flagged with REQ_RAHEAD. This means we don't see it in
blktrace, for instance, which is a shame. We already make assumptions
about ->readpages() just being for read-ahead in the mpage
implementation, using readahead_gfp_mask(mapping) as out GFP mask of
choice.

This small series fixes up mpage_readpages() to submit with
REQ_RAHEAD, which takes care of file systems using mpage_readpages().
The first patch is a prep patch, that makes do_mpage_readpage() take
an argument structure.

Changes since v2:

- Get rid of 'gfp' passing once we have is_readahead
- Pack struct better, makes it 8 bytes smaller.

Changes since v1:

- Fix ext4_mpage_readpages() also being used for regular reads
- Add prep patch with struct arguments for do_mpage_readpage()

 fs/btrfs/extent_io.c |   2 +-
 fs/ext4/ext4.h       |   2 +-
 fs/ext4/inode.c      |   5 +-
 fs/ext4/readpage.c   |   5 +-
 fs/mpage.c           | 115 ++++++++++++++++++++++++-------------------
 5 files changed, 71 insertions(+), 58 deletions(-)