writeback: avoid touching dirtied_when on blocked inodes

Hi,

This tries to keep dirtied_when for blocked inodes by converting some redirty_tail() calls to requeue_io_wait(). The possibly blocked inodes will be moved to b_more_io_wait. The b_more_io_wait inodes will now be retried as dillegent as b_more_io inodes, except when the latter goes empty, b_more_io_wait will be retried by the kupdate work on increasing intervals until exceeding dirty_writeback_interval.

Christoph Hellwig (1):

      writeback: avoid redirtying when ->write_inode failed to clear I_DIRTY

Jan Kara (2):
writeback: update wb->last_active on written pages/inodes
writeback: Retry kupdate work early if we need to retry some inode writeback

Wu Fengguang (4):
writeback: introduce queue b_more_io_wait
writeback: requeue_io_wait() on pages_skipped inode
writeback: requeue_io_wait() on blocked inode
writeback: requeue_io_wait() when failed to grab superblock

 fs/fs-writeback.c           |   62 ++++++++++++++++++++++++++++++++++---------
 include/linux/backing-dev.h |    8 +++--
 mm/backing-dev.c            |   10 +++++-
 3 files changed, 62 insertions(+), 18 deletions(-)

Thanks,
Fengguang