[LTP] [PATCH COMMITTED] tst_device: do sync() before reading test block device stat file

[Cyril Hrubis]

Hi!
> > > To avoid FS deferred IO metadata/cache interferes test result, so we
> > > do sync simply before the tst_dev_bytes_written invocation.
> >
> > Can we do fsync() on the fd instead of full sync()? That should be
> > slightly faster.
> >
> 
> Probably you miss the previous discussed [1], we use sync() here because we
> do want to make sure all FS metadata/cache being written back before the
> testing since there is no obtainable file descriptor 'fd' for the ext4
> deferred IO (e.g. initialize the journal and inode tables).

Ah, right, we measure I/O to the whole device, so we would have to sync
the device in question. Then syncfs() on the fd we got should work
right? And it should avoid syncing unrelated filesystems as well.

-- 
Cyril Hrubis
chrubis@suse.cz