Re: [PATCH 2/3] xfs_scrub: perform media scans of entire devices

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Wed, Nov 06, 2019 at 02:15:43PM -0600, Eric Sandeen wrote:
> On 10/22/19 1:50 PM, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Add a new feature to xfs_scrub where specifying multiple -x will cause
> > it to perform a media scan of the entire disk, not just the file data
> > areas.
> 
> Hm.... convince me why this is useful?  It's likely that any such block
> will get remapped when it's used anyway, right?  What does this help?

It's really only useful as a general media scan, which anyone can do
with ddrescue.  It could potentially be useful if storage reverts to the
old days where writes don't actually remap (flooppies!)....

...eh, let's drop this and the next patch.  I don't even think pmem
behaves like that.

> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > Reviewed-by: Allison Collins <allison.henderson@oracle.com>
> > ---
> >  man/man8/xfs_scrub.8 |    3 +++
> >  scrub/phase6.c       |   60 ++++++++++++++++++++++++++++++++++++++++++++++----
> >  scrub/phase7.c       |    5 ++++
> >  scrub/xfs_scrub.c    |    4 ++-
> >  scrub/xfs_scrub.h    |    1 +
> >  5 files changed, 66 insertions(+), 7 deletions(-)
> > 
> > 
> > diff --git a/man/man8/xfs_scrub.8 b/man/man8/xfs_scrub.8
> > index e881ae76..2cdec380 100644
> > --- a/man/man8/xfs_scrub.8
> > +++ b/man/man8/xfs_scrub.8
> > @@ -97,6 +97,9 @@ Prints the version number and exits.
> >  .TP
> >  .B \-x
> >  Read all file data extents to look for disk errors.
> > +If this option is given more than once, scrub all disk contents.
> 
> This addition doesn't really make clear what -xx does, IMHO.  Something
> more explicit like "look for errors even in freespace?"

Yeah.

> > +If this option is given more than twice, report errors even if they have not
> > +yet caused data loss.
> 
> sooo w/ -xx it'll read freespace but not report errors, with -xxx it will?

The same as -xx.

--D

> 
> -Eric