Re: [PATCH 08/12] xfs: remove xfs_ifork_ops

Darrick J. Wong
2020-05-16T17:48:11Z

On Sat, May 09, 2020 at 07:13:44AM -0400, Brian Foster wrote:
> On Sat, May 09, 2020 at 10:17:15AM +0200, Christoph Hellwig wrote:
> > On Fri, May 08, 2020 at 11:05:43AM -0400, Brian Foster wrote:
> > > On Fri, May 08, 2020 at 08:34:19AM +0200, Christoph Hellwig wrote:
> > > > xfs_ifork_ops add up to two indirect calls per inode read and flush,
> > > > despite just having a single instance in the kernel. In xfsprogs
> > > > phase6 in xfs_repair overrides the verify_dir method to deal with inodes
> > > > that do not have a valid parent, but that can be fixed pretty easily
> > > > by ensuring they always have a valid looking parent.
> > > >
> > > > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > > > ---
> > >
> > > Code looks fine, but I assume we'll want a repair fix completed and
> > > merged before wiping this out:
> >
> > With the xfsprogs merge delays I'm not sure merged will work, but I'll
> > happily take your patch and get it in shape for submission.
> >
>
> The critical bit is that repair is fixed before this lands in xfsprogs,
> otherwise we just reintroduce the regression the callback mechanism was
> designed to fix. The repair change is not huge, but it's not necessarily
> trivial so it's probably worth making sure the repair change is at least
> reviewed before putting this into the kernel pipeline.
>
> BTW, I played with this a bit more yesterday and made some tweaks that I
> think make it a little cleaner. Namely instead of processing the parent
> bits in phases 3 and 4 and setting the parent in the internal structures
> in phase 4, to do everything in phase 3 and skip the repeat checks in
> phase 4. This has the side effect of eliminating some duplicate error
> messages where repair complains about the original bogus value in phase
> 3, sets it to zero, and then complains about the zero value again in
> phase 4. This still needs some auditing to assess whether we're losing
> any extra verification by setting the parent in phase 3, however. It
> also might be worth looking at giving the other dir formats the same
> treatment. Squashed diff of my local tree below...
>
> Brian
>
> diff --git a/repair/dino_chunks.c b/repair/dino_chunks.c
> index 6685a4d2..96ed6a5b 100644
> --- a/repair/dino_chunks.c
> +++ b/repair/dino_chunks.c
> @@ -859,14 +859,7 @@ next_readbuf:
> */
> if (isa_dir) {
> set_inode_isadir(ino_rec, irec_offset);
> - /*
> - * we always set the parent but
> - * we may as well wait until
> - * phase 4 (no inode discovery)
> - * because the parent info will
> - * be solid then.
> - */
> - if (!ino_discovery) {
> + if (ino_discovery) {
> ASSERT(parent != 0);
> set_inode_parent(ino_rec, irec_offset, parent);
> ASSERT(parent ==
> diff --git a/repair/dir2.c b/repair/dir2.c
> index cbbce601..9c789b4a 100644
> --- a/repair/dir2.c
> +++ b/repair/dir2.c
> @@ -165,7 +165,6 @@ process_sf_dir2(
> int tmp_elen;
> int tmp_len;
> xfs_dir2_sf_entry_t *tmp_sfep;
> - xfs_ino_t zero = 0;
>
> sfp = (struct xfs_dir2_sf_hdr *)XFS_DFORK_DPTR(dip);
> max_size = XFS_DFORK_DSIZE(dip, mp);
> @@ -480,6 +479,9 @@ _("corrected entry offsets in directory %" PRIu64 "\n"),
> * check parent (..) entry
> */
> *parent = libxfs_dir2_sf_get_parent_ino(sfp);
> + if (!ino_discovery)
> + return 0;
> +
>
> /*
> * if parent entry is bogus, null it out. we'll fix it later .
> @@ -494,7 +496,7 @@ _("bogus .. inode number (%" PRIu64 ") in directory inode %" PRIu64 ", "),
> if (!no_modify) {
> do_warn(_("clearing inode number\n"));
>
> - libxfs_dir2_sf_put_parent_ino(sfp, zero);
> + libxfs_dir2_sf_put_parent_ino(sfp, mp->m_sb.sb_rootino);
> *dino_dirty = 1;
> *repair = 1;
> } else {
> @@ -529,7 +531,7 @@ _("bad .. entry in directory inode %" PRIu64 ", points to self, "),
> if (!no_modify) {
> do_warn(_("clearing inode number\n"));
>
> - libxfs_dir2_sf_put_parent_ino(sfp, zero);
> + libxfs_dir2_sf_put_parent_ino(sfp, mp->m_sb.sb_rootino);
> *dino_dirty = 1;
> *repair = 1;
> } else {
> diff --git a/repair/phase6.c b/repair/phase6.c
> index beceea9a..43bcea50 100644
> --- a/repair/phase6.c
> +++ b/repair/phase6.c
> @@ -26,58 +26,6 @@ static struct xfs_name xfs_name_dot = {(unsigned char *)".",
> 1,
> XFS_DIR3_FT_DIR};
>
> -/*
> - * When we're checking directory inodes, we're allowed to set a directory's
> - * dotdot entry to zero to signal that the parent needs to be reconnected
> - * during phase 6. If we're handling a shortform directory the ifork
> - * verifiers will fail, so temporarily patch out this canary so that we can
> - * verify the rest of the fork and move on to fixing the dir.
> - */
> -static xfs_failaddr_t
> -phase6_verify_dir(
> - struct xfs_inode *ip)
> -{
> - struct xfs_mount *mp = ip->i_mount;
> - struct xfs_ifork *ifp;
> - struct xfs_dir2_sf_hdr *sfp;
> - xfs_failaddr_t fa;
> - xfs_ino_t old_parent;
> - bool parent_bypass = false;
> - int size;
> -
> - ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
> - sfp = (struct xfs_dir2_sf_hdr *)ifp->if_u1.if_data;
> - size = ifp->if_bytes;
> -
> - /*
> - * If this is a shortform directory, phase4 may have set the parent
> - * inode to zero to indicate that it must be fixed. Temporarily
> - * set a valid parent so that the directory verifier will pass.
> - */
> - if (size > offsetof(struct xfs_dir2_sf_hdr, parent) &&
> - size >= xfs_dir2_sf_hdr_size(sfp->i8count)) {
> - old_parent = libxfs_dir2_sf_get_parent_ino(sfp);
> - if (old_parent == 0) {
> - libxfs_dir2_sf_put_parent_ino(sfp, mp->m_sb.sb_rootino);
> - parent_bypass = true;
> - }
> - }
> -
> - fa = libxfs_default_ifork_ops.verify_dir(ip);
> -
> - /* Put it back. */
> - if (parent_bypass)
> - libxfs_dir2_sf_put_parent_ino(sfp, old_parent);
> -
> - return fa;
> -}
> -
> -static struct xfs_ifork_ops phase6_ifork_ops = {
> - .verify_attr = xfs_attr_shortform_verify,
> - .verify_dir = phase6_verify_dir,
> - .verify_symlink = xfs_symlink_shortform_verify,
> -};
> -
> /*
> * Data structures used to keep track of directories where the ".."
> * entries are updated. These must be rebuilt after the initial pass
> @@ -1104,7 +1052,7 @@ mv_orphanage(
> (unsigned long long)ino, ++incr);
>
> /* Orphans may not have a proper parent, so use custom ops here */
> - err = -libxfs_iget(mp, NULL, ino, 0, &ino_p, &phase6_ifork_ops);
> + err = -libxfs_iget(mp, NULL, ino, 0, &ino_p, &xfs_default_ifork_ops);

Hmm. I'll have to look at this more thoroughly on a non-weekend, but I
think I like this approach, since it removes the weird quirk that if
repair fails after writing out a sf directory with parent==0, we'll have
transformed an fs with bad directory parent pointers to an fs with a
directory that totally fails the verifier.

So for the kernel patch, provisionally:
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> if (err)
> do_error(_("%d - couldn't iget disconnected inode\n"), err);
>
> @@ -2875,7 +2823,7 @@ process_dir_inode(
>
> ASSERT(!is_inode_refchecked(irec, ino_offset) || dotdot_update);
>
> - error = -libxfs_iget(mp, NULL, ino, 0, &ip, &phase6_ifork_ops);
> + error = -libxfs_iget(mp, NULL, ino, 0, &ip, &xfs_default_ifork_ops);
> if (error) {
> if (!no_modify)
> do_error(
>