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"....
> + 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...
> +/* Scrub an inobt/finobt record. */
> +STATIC int
> +xfs_scrub_iallocbt_helper(
s/helper/rec/
-Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
--
To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
