This cleanup patch gives several improvements:

 - Moving all kmem_cache_{create_destroy} calls into one place, which removes
 some small function calls, cleans up error check code and clarify the logic.

 - Mark all initial code in __init section.

 - Remove some very obvious comments.

 - Adjust some declarations.

 - Fix some space-tab issues.
Signed-off-by: NLi Hong <lihong.hi@gmail.com>
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This moves out checksum routines in log writer to segbuf.c for
cleanup.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This moves a pointer to buffer storing super root block to each log
buffer from nilfs_sc_info struct for simplicity.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This moves iterator to submit write requests for a series of logs into
segbuf.c, and hides nilfs_segbuf_write() and nilfs_segbuf_wait() in
the file.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This separates wait function for submitted logs from the write
function nilfs_segctor_write().  A new list of segment buffers
"sc_write_logs" is added to hold logs under writing, and double
buffering is partially applied to hide io latency.

At this point, the double buffering is disabled for blocksize <
pagesize because page dirty flag is turned off during write and dirty
buffers are not properly collected for pages crossing over segments.

To receive full benefit of the double buffering, further refinement is
needed to move the io wait outside the lock section of log writer.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This adds a few iterator functions for segment buffers to make it easy
to handle multiple series of logs.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Hides nilfs_write_info struct and nilfs_segbuf_prepare_write function
in segbuf.c to simplify the interface of nilfs_segbuf_write function.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This moves io status variables in nilfs_write_info struct to
nilfs_segment_buffer struct.

This is a preparation to hide nilfs_write_info in segment buffer code.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

will reduce some lines of segment constructor.  Previously, the state was
complexly controlled through a list of segments in order to keep
consistency in meta data of usage state of segments.  Instead, this
presents ``calculated'' active flags to userland cleaner program and stop
maintaining its real flag on disk.

Only by this fake flag, the cleaner cannot exactly know if each segment is
reclaimable or not.  However, the recent extension of nilfs_sustat ioctl
struct (nilfs2-extend-nilfs_sustat-ioctl-struct.patch) can prevent the
cleaner from reclaiming in-use segment wrongly.

So, now I can apply this for simplification.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This adds the segment buffer which is used to constuct logs.

[akpm@linux-foundation.org: BIO_RW_SYNC got removed]
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>