[PATCH v6 0/1] nilfs2: add missing blkdev_issue_flush() to nilfs_sync_fs()

[Andreas Rohner]

Hi,

I have looked a bit more into the semantics of the various flags
concerning block device caching behaviour. According to
"Documentation/block/writeback_cache_control.txt" a call to
blkdev_issue_flush() is equivalent to an empty bio with the
REQ_FLUSH flag set. So there is no need to call blkdev_issue_flush()
after a call to nilfs_commit_super(). But if there is no need to write
the super block an additional call to blkdev_issue_flush() is necessary.

To avoid an overhead I introduced the nilfs->ns_flushed_device flag,
which is set to 0 whenever new logs are written and set to 1 whenever
the block device is flushed. If the super block was written during
segment construction or in nilfs_sync_fs(), then blkdev_issue_flush() is
not called.

br,
Andreas Rohner

v5->v6 (review by Ryusuke Konishi)
* Remove special handling of EIO error state from nilfs_ioctl_sync()

v4->v5 (review by Ryusuke Konishi)
* Move device flushing logic into separate function
* Fix invalid comment
* Move clearing of the flag to nilfs_segctor_complete_write() and
nilfs_construct_dsync_segment()

v3->v4 (review by Ryusuke Konishi)
* Replace atomic_t with int for ns_flushed_device
* Use smp_wmb() to guarantee correct ordering

v2->v3 (review of Ryusuke Konishi)
* Use separate atomic flag for ns_flushed_device instead of a bit flag
in ns_flags
* Use smp_mb__after_atomic() after setting ns_flushed_device

v1->v2
* Add new flag THE_NILFS_FLUSHED

Andreas Rohner (1):
nilfs2: add missing blkdev_issue_flush() to nilfs_sync_fs()

fs/nilfs2/file.c | 8 +++-----
fs/nilfs2/ioctl.c | 8 +++-----
fs/nilfs2/segment.c | 3 +++
fs/nilfs2/super.c | 6 ++++++
fs/nilfs2/the_nilfs.h | 22 ++++++++++++++++++++++
5 files changed, 37 insertions(+), 10 deletions(-)