Re: [RFC PATCH V3] xfsrestore: fix rootdir due to xfsdump bulkstat misuse

[Carlos Maiolino <cem@kernel.org>]

Hi Darrick.

> > >> This patch adds a '-x' option (another awkward thing is that
> > >> the codebase doesn't support long options) to address
> > >> problamatic images by searching for the real dir, the reason
> > >> that I don't enable it by default is that I'm not very confident
> > >> with the xfsrestore codebase and xfsdump bulkstat issue will
> > >> also be fixed immediately as well, so this function might be
> > >> optional and only useful for pre-exist corrupted dumps.
> > >
> > > As far as fixing xfsdump -- wasn't XFS_BULK_IREQ_SPECIAL_ROOT supposed
> > > to solve that problem by enabling dump to discover it it's really been
> > > passed the fs root directory?
> >
> > Yes, but as I understand it this patch is to allow the user to recover
> > from an already corrupted dump, at restore time, right?
> 
> Right, though I still haven't seen any patches to dump to employ
> XFS_BULK_IREQ_SPECIAL_ROOT to avoid spitting out bad dumps in the first
> place.  I think the heuristic that we applied is probably good enough,
> but we might as well query the kernel when possible.
> 
> > This still feels like deep magic in xfsdump that most people struggle
> > to understand, but it seems clear to me that the changes here are truly
> > isolated to the new "-x" option - IOWs if "-x" is not specified, there is
> > no behavior change at all.
> >
> > Since this is intended to attempt recovery from an already-corrupted
> > dump image as a last resort, and given that there are already some xfstests
> > in place to validate the behavior, I feel reasonably comfortable with
> > merging this.
> 
> Documentation nit: Can restore detect that it's been given a corrupt
> dump, and if so, should it warn the user to rerun with -x?
> 
> --D

I am assuming that even though you have concerns about not having
XFS_BULK_IREQ_SPECIAL_ROOT employed in dump yet (and the documentation nit :),
you are not opposed to have this patch merged?


-- 
Carlos Maiolino