Re: [PATCH 01/10] db: increase metadump's default overly long extent discard threshold

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

On Thu, Oct 26, 2017 at 07:03:15PM -0500, Eric Sandeen wrote:
> On 10/26/17 5:14 PM, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > 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>
> > Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
> 
> Thanks, I'll pull this in.
> 
> Should we fix the noisiness so it doesn't require -w for 
> warnings as well?

Yeah.  Seeing as we can't have an extent that long anyway we could
possibly promote it to a flat out error message, at least if it's
set to 2097151.

--D

> -Eric
> 
> > ---
> >  db/metadump.c           |    2 +-
> >  man/man8/xfs_metadump.8 |    2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > 
> > diff --git a/db/metadump.c b/db/metadump.c
> > index 6dd06c3..8ffb90f 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
> > diff --git a/man/man8/xfs_metadump.8 b/man/man8/xfs_metadump.8
> > index 3731d6a..7207c20 100644
> > --- a/man/man8/xfs_metadump.8
> > +++ b/man/man8/xfs_metadump.8
> > @@ -114,7 +114,7 @@ copied.
> >  .B \-m
> >  Set the maximum size of an allowed metadata extent.  Extremely large metadata
> >  extents are likely to be corrupt, and will be skipped if they exceed
> > -this value.  The default size is 1000 blocks.
> > +this value.  The default size is 2097151 blocks.
> >  .TP
> >  .B \-o
> >  Disables obfuscation of file names and extended attributes.
> > 
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