Re: [PATCH 1/2] xfs: assert that xattr inactivation never reaches a hole

[Brian Foster <bfoster@redhat.com>]

On Tue, Oct 10, 2017 at 09:55:46AM -0700, Darrick J. Wong wrote:
> On Tue, Oct 10, 2017 at 12:47:55PM -0400, Brian Foster wrote:
> > The child buffer read in xfs_attr3_node_inactive() should never
> > reach a hole in the attr fork. If this occurs, it is likely due to a
> > bug. Prior to commit cd87d867 ("xfs: don't crash on unexpected holes
> > in dir/attr btrees"), this would result in a crash. Now that the
> > crash has been fixed, this is a silent failure.
> > 
> > Add an assert in this codepath to detect this particular condition.
> > Note that the right fix here may be to pass -1 to
> > xfs_da3_node_read() such that a hole returns an error. This is a
> > cautious first step in that direction.
> > 
> > Signed-off-by: Brian Foster <bfoster@redhat.com>
> > ---
> >  fs/xfs/xfs_attr_inactive.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/fs/xfs/xfs_attr_inactive.c b/fs/xfs/xfs_attr_inactive.c
> > index ebd66b1..6b4f5c6 100644
> > --- a/fs/xfs/xfs_attr_inactive.c
> > +++ b/fs/xfs/xfs_attr_inactive.c
> > @@ -255,6 +255,7 @@ xfs_attr3_node_inactive(
> >  						XFS_ATTR_FORK);
> >  		if (error)
> >  			return error;
> > +		ASSERT(child_bp);
> 
> xfs_dabuf_map will log an error message and return -EFSCORRUPTED if
> mappedbno == -1, so (afaict) you might as well do that instead of adding
> the ASSERT.  We'll still see the dmesg report.
> 

Yep, noted above. I wasn't sure if we wanted to fail the broader
inactivate, but I'm Ok with it if you are. :) I'll run some tests with
that change instead.

Brian

> --D
> 
> >  		if (child_bp) {
> >  						/* save for re-read later */
> >  			child_blkno = XFS_BUF_ADDR(child_bp);
> > -- 
> > 2.9.5
> > 
> > --
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