Pass1c is responsible for analyzing extended attributes, and
it works off a linked list of items built in pass1. I see no
reason why we can't eliminate the linked list and have pass1
do the analysis while it's checking each dinode. It seems logical
to assume that it was moved to follow pass1b (duplicate reference
processing) for a reason, so we need to determine if that's still
necessary, given today's improved pass1 logic.

I'm going to investigate whether we can eliminate pass1c altogether.
Between pass1 and pass1b, I think we do almost everything necessary
from pass1c with regard to extended attributes.

I plan to do a detailed examination of pass1c to see if it does
anything important, and if so, whether that can be safely moved
to pass1.

Reassigning to myself.

I've done a thorough examination of pass1c. In my opinion, there's
no reason not to perform its checks inside of pass1. That saves
us from building the linked list, chewing up all that memory and
time to make another pass through the file system.

I've coded a patch that completely eliminates pass1c from fsck
and moves its checks to the appropriate places in pass1c.c.
I'm testing it now against my latest collection of metadata.

Created attachment 1071846 [details]
Early prototype #1

This prototype eliminates pass1c in favor of simple checks
added to pass1.

I'm making good progress, but this turns out to be a bigger project
than I anticipated. I'm finding some nasty bugs in fsck.gfs2 related
to extended attributes and how we deal with them. I'm testing a new
prototype now. I'll attach it when it gets further along in testing.

Created attachment 1077949 [details]
Set of 20 RHEL7 patches - posted and tested

This tarball contains a set of 20 patches that I posted today:

0000-cover-letter.patch
0001-libgfs2-Check-block-range-when-inserting-into-rgrp-t.patch
0002-libgfs2-Check-rgd-bits-before-referencing-it.patch
0003-fsck.gfs2-Add-check-for-gfs1-invalid-inode-refs-in-d.patch
0004-fsck.gfs2-Make-debug-messages-more-succinct-wrt-exte.patch
0005-fsck.gfs2-Break-up-funtion-handle_dup_blk.patch
0006-fsck.gfs2-Only-preserve-the-_first_-acceptable-inode.patch
0007-fsck.gfs2-Don-t-just-assume-the-remaining-EA-referen.patch
0008-fsck.gfs2-Don-t-delete-inode-for-duplicate-reference.patch
0009-fsck.gfs2-Don-t-traverse-EAs-that-belong-to-another-.patch
0010-fsck.gfs2-Refactor-function-check_indirect_eattr.patch
0011-fsck.gfs2-Once-an-indirect-ea-error-is-found-flag-al.patch
0012-fsck.gfs2-Always-restore-saved-value-for-di_eattr.patch
0013-fsck.gfs2-Remove-redundancy-in-add_duplicate_ref.patch
0014-fsck.gfs2-Don-t-remove-duplicate-eattr-blocks.patch
0015-fsck.gfs2-Refactor-check_eattr_entries-and-add-error.patch
0016-fsck.gfs2-remove-bad-EAs-at-the-end-not-as-you-go.patch
0017-fsck.gfs2-Combine-remove_inode_eattr-with-its-only-c.patch
0018-fsck.gfs2-Print-debug-message-to-dilineate-metadata-.patch
0019-fsck.gfs2-Remove-pass1c-in-favor-of-processing-in-pa.patch
0020-fsck.gfs2-Clone-duplicate-data-block-pointers.patch

Bumping to 7.3.

Changing status to POST. These patches were tested against my entire
metadata collection. They were posted to cluster-devel, and then
pushed to the gfs2-utils master branch. Our current plan is to
rebase RHEL7.3 from master, as per a discussion I had with Andy Price
this morning. Therefore I'm setting this to POST and we'll make it
dependent on the rebase bz.

This bug was accidentally moved from POST to MODIFIED via an error in automation, please see mmccune with any questions

https://brewweb.engineering.redhat.com/brew/buildinfo?buildID=498444

pass1c was removed and testing on gfs2-utils-3.1.9-3.el7.x86_64 shows that pass1 is scaling nearly linear from 256GB to 8TB.

256G fsck80: elapsed =  0:29:24.42, pass1 =   1760, pass1b = 0, pass2 =   2, pass3 = 0, pass4 = 0, maxresident = 0.02GB
512G fsck80: elapsed =  0:56:01.83, pass1 =   3353, pass1b = 0, pass2 =   4, pass3 = 0, pass4 = 0, maxresident = 0.04GB
  1T fsck80: elapsed =  2:31:13.00, pass1 =   9055, pass1b = 0, pass2 =  11, pass3 = 0, pass4 = 0, maxresident = 0.09GB
  2T fsck80: elapsed =  6:25:06.00, pass1 =  23068, pass1b = 0, pass2 =  22, pass3 = 0, pass4 = 1, maxresident = 0.18GB
  4T fsck80: elapsed = 14:52:42.00, pass1 =  53481, pass1b = 0, pass2 =  53, pass3 = 0, pass4 = 2, maxresident = 0.35GB
  8T fsck80: elapsed = 29:20:49.00, pass1 = 105445, pass1b = 0, pass2 = 169, pass3 = 0, pass4 = 5, maxresident = 0.68GB

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-2438.html