Re: [PATCH] db: increase metadump's default overly long extent discard threshold

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

On Tue, Sep 26, 2017 at 09:21:37PM -0500, Eric Sandeen wrote:
> On 9/26/17 8:02 PM, Darrick J. Wong wrote:
> > Back in 88b8e1d6d7 ("Make xfs_metadump more robust against bad data"),
> > metadump grew the ability to ignore a directory extent if it was longer
> > than 20 blocks.  Presumably this was to protect metadump from dumping
> > absurdly long extents resulting from bmbt corruption, but it's certainly
> > possible to create a directory with an extent longer than 20 blocks.
> > Hilariously, the discards happen with no warning unless the caller
> > explicitly set -w.
> > 
> > This was raised to 1000 blocks in 7431d134fe8 ("Increase default maximum
> > extent size for xfs_metadump when copying..."), but it's still possible
> > to create a directory with an extent longer than 1000 blocks.
> > 
> > Increase the threshold to MAXEXTLEN blocks because it's totally valid
> > for the filesystem to create extents up to that length.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> 
> This is documented in the manpage as being 1000, so that needs an update
> as well.  

Ok.

> And should the warning be made unconditional, if that's what burned
> you?

Nah, since most of the other warnings in metadump are about things that
look like bad metadata.

--D

> 
> -Eric
> 
> > ---
> >  db/metadump.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/db/metadump.c b/db/metadump.c
> > index c179480..c8eb8f0 100644
> > --- a/db/metadump.c
> > +++ b/db/metadump.c
> > @@ -32,7 +32,7 @@
> >  #include "field.h"
> >  #include "dir2.h"
> >  
> > -#define DEFAULT_MAX_EXT_SIZE	1000
> > +#define DEFAULT_MAX_EXT_SIZE	MAXEXTLEN
> >  
> >  /*
> >   * It's possible that multiple files in a directory (or attributes
> > 
> 
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