[Ocfs2-devel] [PATCH] ocfs2: improve fsync efficiency and fix deadlock between aio_write and sync_file

[Mark Fasheh]

On Wed, Jan 29, 2014 at 07:48:48PM -0800, Darrick J. Wong wrote:
> Currently, ocfs2_sync_file grabs i_mutex and forces the current
> journal transaction to complete.  This isn't terribly efficient, since
> sync_file really only needs to wait for the last transaction involving
> that inode to complete, and this doesn't require i_mutex.
> 
> Therefore, implement the necessary bits to track the newest tid
> associated with an inode, and teach sync_file to wait for that instead
> of waiting for everything in the journal to commit.  Furthermore, only
> issue the flush request to the drive if jbd2 hasn't already done so.
> 
> This also eliminates the deadlock between ocfs2_file_aio_write() and
> ocfs2_sync_file().  aio_write takes i_mutex then calls
> ocfs2_aiodio_wait() to wait for unaligned dio writes to finish.
> However, if that dio completion involves calling fsync, then we can
> get into trouble when some ocfs2_sync_file tries to take i_mutex.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>

Ok, I can see what the patch is doing, but I have a silly question - where
exactly are we marking the latest transaction id during a write system call?
	--Mark

--
Mark Fasheh