Re: [PATCH 6/9] xfs: inode scrubber shouldn't bother with raw checks

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

On Wed, Mar 21, 2018 at 01:42:39PM -0400, Brian Foster wrote:
> On Wed, Mar 14, 2018 at 05:30:07PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > The inode scrubber tries to _iget the inode prior to running checks.
> > If that _iget call fails with corruption errors that's an automatic
> > fail, regardless of whether it was the inode buffer read verifier,
> > the ifork verifier, or the ifork formatter that errored out.
> > 
> > Therefore, get rid of the raw mode scrub code because it's not needed.
> > Found by trying to fix some test failures in xfs/379 and xfs/415.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  fs/xfs/scrub/inode.c |   98 +++++---------------------------------------------
> >  1 file changed, 9 insertions(+), 89 deletions(-)
> > 
> > 
> > diff --git a/fs/xfs/scrub/inode.c b/fs/xfs/scrub/inode.c
> > index 21297be..0332a01 100644
> > --- a/fs/xfs/scrub/inode.c
> > +++ b/fs/xfs/scrub/inode.c
> > @@ -515,72 +515,6 @@ xfs_scrub_dinode(
> >  	}
> >  }
> >  
> > -/* Map and read a raw inode. */
> > -STATIC int
> > -xfs_scrub_inode_map_raw(
> > -	struct xfs_scrub_context	*sc,
> > -	xfs_ino_t			ino,
> > -	struct xfs_buf			**bpp,
> > -	struct xfs_dinode		**dipp)
> > -{
> > -	struct xfs_imap			imap;
> > -	struct xfs_mount		*mp = sc->mp;
> > -	struct xfs_buf			*bp = NULL;
> > -	struct xfs_dinode		*dip;
> > -	int				error;
> > -
> > -	error = xfs_imap(mp, sc->tp, ino, &imap, XFS_IGET_UNTRUSTED);
> > -	if (error == -EINVAL) {
> > -		/*
> > -		 * Inode could have gotten deleted out from under us;
> > -		 * just forget about it.
> > -		 */
> > -		error = -ENOENT;
> > -		goto out;
> > -	}
> > -	if (!xfs_scrub_process_error(sc, XFS_INO_TO_AGNO(mp, ino),
> > -			XFS_INO_TO_AGBNO(mp, ino), &error))
> > -		goto out;
> > -
> > -	error = xfs_trans_read_buf(mp, sc->tp, mp->m_ddev_targp,
> > -			imap.im_blkno, imap.im_len, XBF_UNMAPPED, &bp,
> > -			NULL);
> > -	if (!xfs_scrub_process_error(sc, XFS_INO_TO_AGNO(mp, ino),
> > -			XFS_INO_TO_AGBNO(mp, ino), &error))
> > -		goto out;
> > -
> > -	/*
> > -	 * Is this really an inode?  We disabled verifiers in the above
> > -	 * xfs_trans_read_buf call because the inode buffer verifier
> > -	 * fails on /any/ inode record in the inode cluster with a bad
> > -	 * magic or version number, not just the one that we're
> > -	 * checking.  Therefore, grab the buffer unconditionally, attach
> > -	 * the inode verifiers by hand, and run the inode verifier only
> > -	 * on the one inode we want.
> > -	 */
> > -	bp->b_ops = &xfs_inode_buf_ops;
> > -	dip = xfs_buf_offset(bp, imap.im_boffset);
> > -	if (xfs_dinode_verify(mp, ino, dip) != NULL ||
> > -	    !xfs_dinode_good_version(mp, dip->di_version)) {
> > -		xfs_scrub_ino_set_corrupt(sc, ino, bp);
> > -		goto out_buf;
> > -	}
> > -
> > -	/* ...and is it the one we asked for? */
> > -	if (be32_to_cpu(dip->di_gen) != sc->sm->sm_gen) {
> > -		error = -ENOENT;
> > -		goto out_buf;
> > -	}
> > -
> > -	*dipp = dip;
> > -	*bpp = bp;
> > -out:
> > -	return error;
> > -out_buf:
> > -	xfs_trans_brelse(sc->tp, bp);
> > -	return error;
> > -}
> > -
> >  /*
> >   * Make sure the finobt doesn't think this inode is free.
> >   * We don't have to check the inobt ourselves because we got the inode via
> > @@ -727,43 +661,29 @@ xfs_scrub_inode(
> >  	struct xfs_scrub_context	*sc)
> >  {
> >  	struct xfs_dinode		di;
> > -	struct xfs_buf			*bp = NULL;
> > -	struct xfs_dinode		*dip;
> > -	xfs_ino_t			ino;
> >  	int				error = 0;
> >  
> > -	/* Did we get the in-core inode, or are we doing this manually? */
> > -	if (sc->ip) {
> > -		ino = sc->ip->i_ino;
> > -		xfs_inode_to_disk(sc->ip, &di, 0);
> > -		dip = &di;
> > -	} else {
> > -		/* Map & read inode. */
> > -		ino = sc->sm->sm_ino;
> > -		error = xfs_scrub_inode_map_raw(sc, ino, &bp, &dip);
> > -		if (error || !bp)
> > -			goto out;
> > +	/* iget failed means automatic fail. */
> > +	if (!sc->ip) {
> > +		xfs_scrub_ino_set_corrupt(sc, sc->sm->sm_ino, NULL);
> > +		return 0;
> >  	}
> 
> Ok, so the setup function will attempt to lookup the inode number that's
> passed in. If the lookup fails with a corruption error, we'd have ip ==
> NULL but return 0 from that setup call because it's not a scrub
> operational error. Hence, we get here without an inode and call it an fs
> corruption. Seems fine as long as I'm following this correctly:

Correct.  I'll change the comment to read:

/*
 * If sc->ip is NULL, that means that the setup function called xfs_iget
 * to look up the inode.  xfs_iget returned a EFSCORRUPTED and a NULL
 * inode, so flag the corruption error and return.
 */

--D

> Reviewed-by: Brian Foster <bfoster@redhat.com>
> 
> >  
> > -	xfs_scrub_dinode(sc, bp, dip, ino);
> > +	/* Scrub the inode core. */
> > +	xfs_inode_to_disk(sc->ip, &di, 0);
> > +	xfs_scrub_dinode(sc, NULL, &di, sc->ip->i_ino);
> >  	if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
> >  		goto out;
> >  
> > -	/* Now let's do the things that require a live inode. */
> > -	if (!sc->ip)
> > -		goto out;
> > -
> >  	/*
> >  	 * Look for discrepancies between file's data blocks and the reflink
> >  	 * iflag.  We already checked the iflag against the file mode when
> >  	 * we scrubbed the dinode.
> >  	 */
> >  	if (S_ISREG(VFS_I(sc->ip)->i_mode))
> > -		xfs_scrub_inode_check_reflink_iflag(sc, ino, bp);
> > +		xfs_scrub_inode_check_reflink_iflag(sc, sc->ip->i_ino, NULL);
> >  
> > -	xfs_scrub_inode_xref(sc, ino, dip);
> > +	xfs_scrub_inode_xref(sc, sc->ip->i_ino, &di);
> >  out:
> > -	if (bp)
> > -		xfs_trans_brelse(sc->tp, bp);
> >  	return error;
> >  }
> > 
> > --
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