On Mon, Oct 16, 2017 at 01:55:59PM +1100, Dave Chinner wrote:
> On Wed, Oct 11, 2017 at 06:42:41PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > Check the records of the inode btrees to make sure that the values
> > make sense given the inode records themselves.
>
> .....
>
> I think maybe I missed this first time around...
>
> > +/* Check a particular inode with ir_free. */
> > +STATIC int
> > +xfs_scrub_iallocbt_check_cluster_freemask(
> > + struct xfs_scrub_btree *bs,
> > + xfs_ino_t fsino,
> > + xfs_agino_t chunkino,
> > + xfs_agino_t clusterino,
> > + struct xfs_inobt_rec_incore *irec,
> > + struct xfs_buf *bp)
> > +{
> > + struct xfs_dinode *dip;
> > + struct xfs_mount *mp = bs->cur->bc_mp;
> > + bool freemask_ok;
> > + bool inuse;
> > + int error;
> > +
> > + dip = xfs_buf_offset(bp, clusterino * mp->m_sb.sb_inodesize);
> > + if (be16_to_cpu(dip->di_magic) != XFS_DINODE_MAGIC ||
> > + (dip->di_version >= 3 &&
> > + be64_to_cpu(dip->di_ino) != fsino + clusterino)) {
> > + xfs_scrub_btree_set_corrupt(bs->sc, bs->cur, 0);
> > + goto out;
> > + }
> > +
> > + freemask_ok = (irec->ir_free & XFS_INOBT_MASK(chunkino + clusterino));
>
> Ok, so if the inode if free, the corresponding bit in the mask
> will be set....
>
> > + error = xfs_icache_inode_is_allocated(mp, bs->cur->bc_tp,
> > + fsino + clusterino, &inuse);
> > + if (error == -ENODATA) {
> > + /* Not cached, just read the disk buffer */
> > + freemask_ok ^= !!(dip->di_mode);
>
> And this uses the lowest bit of the mask? How does that work?
>
> /me spends 10 minutes trying to work out this function before he
> realises that freemask_ok is a boolean, so the initial freemask
> bit is collapsed down to a single bit.
>
> Ok, that's definitely unexpected and not obvious from the code or
> comments. The name "freemask_ok" is misleading the way it's used.
> The first time it is set is means "inode is free", then after this
> operation it means "inode matches free mask"....
Ugh, sorry. Thank you for complaining about this!
>
> > + if (!bs->sc->try_harder && !freemask_ok)
> > + return -EDEADLOCK;
> > + } else if (error < 0) {
> > + /*
> > + * Inode is only half assembled, or there was an IO error,
> > + * or the verifier failed, so don't bother trying to check.
> > + * The inode scrubber can deal with this.
> > + */
> > + freemask_ok = true;
>
> And here it means "we didn't check the free mask"
>
> > + } else {
> > + /* Inode is all there. */
> > + freemask_ok ^= inuse;
>
> And here is means "inode matches free mask" again....
>
> > + }
> > + if (!freemask_ok)
> > + xfs_scrub_btree_set_corrupt(bs->sc, bs->cur, 0);
> > +out:
> > + return 0;
>
> Can we rewrite this to be a little more obvious?
>
> bool inode_is_free = false;
> bool freemask_ok;
> ....
> if (irec->ir_free & XFS_INOBT_MASK(chunkino + clusterino))
> inode_is_free = true;
> ....
> if (error == -ENODATA) {
> freemask_ok = inode_is_free ^ !!(dip->di_mode);
> ....
> else if (error < 0) {
> /*
> * Inode is only half assembled, .....
> */
> goto out;
> } else {
> freemask_ok = inode_is_free ^ inuse;
> }
>
> That's a lot more obvious what the code is checking...
Done.
>
> > +/* Scrub an inobt/finobt record. */
> > +STATIC int
> > +xfs_scrub_iallocbt_helper(
>
> s/helper/rec/
Done.
--D
>
> -Dave.
> --
> Dave Chinner
> david@xxxxxxxxxxxxx
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