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Re: [PATCH 00/30] xfsprogs: Initial CRC support

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 00/30] xfsprogs: Initial CRC support
From: "Michael L. Semon" <mlsemon35@xxxxxxxxx>
Date: Sat, 18 May 2013 01:40:39 -0400
Cc: xfs@xxxxxxxxxxx
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On 05/17/2013 11:25 PM, Dave Chinner wrote:
On Fri, May 17, 2013 at 04:54:47PM -0400, Michael L. Semon wrote:
On 05/17/2013 07:12 AM, Dave Chinner wrote:
Hi Folks,

This is the first real "works ok" CRC patchset for xfsprogs. It
provides full support for mkfs.xfs and xfs_repair, and partial
read-only support for xfs_db.

For mkfs.xfs, it does everything properly, and filesystems that are
freshly made also run cleanly through xfs_repair and mount and run
just fine.

For xfs_repair, it reads and writes all metadata with CRC checks,
calculations and validation just like the kernel code does, but it
currently silently ignores the validation done in the IO layer.
Enabling that is future work - it involves adding buffer error checking to
every libxfs_readbuf() call that is made, and we do none of that
right now. It does, however, fully validate all the non-CRC format
metadata just as it does for non-CRC filesystems, and so the
coverage it has is the same for both CRC and non-CRC filesystems.

For xfs_db, there is read-only support for looking at the filesystem
as the xfs_db IO stack does not support CRCs at all. We need to
convert xfs_db to use the libxfs infrastructure to enable that.
Apart from that, xfs_db has partial support for the extended
metadata fields - the directory/attribute blocks don't have extended
support yet, but everything else does.

xfs_check is made special. It currently detects a version 5
superblock, and immediately exits with success. Hence it always says
CRC enabled filesystems are OK. This is a temporary change that
enables running xfstests without full support in xfs_db for all the
new metadata structures (like headers in remote symlink and
attribute blocks). Depending on if we want to keep xfs-check useful
for xfstests, we can revisit this bypass hack once xfs_db has been
converted to use the libxfs IO engine.

Overall, xfstests is now running enough to start to find bugs in the
kernel CRC code - I'm mainly hitting remote attribute block bugs
right now (generic/117!) but there's certainly less problems being
reported than I expected.

Oh, and I've tested it with external log devices and real time
devices, too.

Comments, thoughts, flames, and testing all welcome!



OK.  The basics look good so far.  The patchset applied without need
for additional work with vi and patch.  Whitespace errors were
reported for Patches 8, 14, 16, 17, 24, 25, and 27.  xfsprogs built
with no additional errors over a normal xfsprogs build.

Can you send me the output indicating where the whitespace errors
are? I don't get any warnings from guilt about them when I apply the
patchset here...

If it makes any difference at all, I'm saving these patches using Thunderbird...

The pre-patchset xfsprogs has been saved as a tarball, so I can provide a non-git patch session if necessary. Sorry so vague last time: I was overjoyed that everything went through git so cleanly.

This is the result of the patches about which `git am` complained:


Applying: libxfs: add support for crc headers on remote symlinks
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:282: new blank line at EOF.


Applying: xfs: add CRCs to dir2/da node blocks
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:61: trailing whitespace.
                                        nodehdr.level, id->ino,
warning: 1 line adds whitespace errors.


Applying: xfs: split remote attribute code out
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:722: new blank line at EOF.
warning: 1 line adds whitespace errors.


Applying: xfs: add CRC protection to remote attributes
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:340: trailing whitespace.
         * allocating the blocks below.
warning: 1 line adds whitespace errors.


Applying: xfsprogs: add crc format support to repair
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:574: trailing whitespace.
if (scan_lbtree(be64_to_cpu(pp[i]), level, scan_bmapbt, type,
warning: 1 line adds whitespace errors.


Applying: xfs_repair: update for dir/attr crc format changes.
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:128: trailing whitespace.
                if ((leafhdr.holes == 0 &&
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:130: space before tab in indent.
                                leafhdr.firstused > firstb)  {
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:136: trailing whitespace.
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:146: trailing whitespace.
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:158: trailing whitespace.
warning: squelched 1 whitespace error
warning: 6 lines add whitespace errors.


Applying: xfs_db: disable modification for CRC enabled filessytems.
/usr/src/xfs/xfsprogs/.git/rebase-apply/patch:20: trailing whitespace.
warning: 1 line adds whitespace errors.

That all stated, the `tar -xvf qt-source.tar.xz` still fails on a
CRC-enabled filesystem.

Not surprising - I haven't got a crc enabled filesystem all the way
through xfstests yet. remote attributes are the current piece I'm
working on getting fixed.

Worse, until I return home, I won't be able
to do serial-console capture of hard oopses.  However, the initial
oops I got was a soft one, so it is included after my closing.  The
kernel is this...

last night's kernel git

last night's xfs-oss/master

some of your recent patches (didn't apply your 6_5 patch yet)

J. Liu's most recent patchset + 2 older bitness patches

Chandra's v8 pquota/gquota patchset + one E-mail fix

Shaggy's JFS patch to make it through the old xfstests #068 on JFS

an NILFS2 patch to address broken bmap handling, lurked from the
NILFS2 mailing list

one local removed assert to make it through the old xfstests #111

maybe one or two XFS patches beyond this

...all on a 32-bit Pentium 4.

And reporting bugs :)

What I'm trying to state is that a lot is in there, but the PC is
spinning like a top, and xfstests results are really good right now.
However, if I feel the need to provide a fresh environment, patch
management is taking some time.

How are you managing patches right now? When taking in a new
patchset from a mailing list, I save them all in a mbox file,
then use git-am to apply them to a temporary git branch. I then move
to my real working branch, and do a 'guilt import-commit x..y' to
convert the commits in the temporary branch to a set of guilt
patches, and then go from there....

The patches themselves are stored as individual files, in case they need to be applied again. Separate git branches are used for kernel patches, but for the XFS suite, I keep backup tarballs and work directly off of master.

A new branch is started at strategic points. If you mention "this is based on 3.9.2 + xfsdev", kernel 3.9.2 is checked out into a new branch, xfs-oss/master is updated and merged, and the patches are reapplied. It takes time but is the best way, until I can find the `git --backout-this-patch-cleanly --i-really-mean-it-this-time --do-not-bother-to-suggest-git-am-resolved-if-it-cannot-be-done` command.

The trick is to remember which patches to apply, so I might have a directory that has five great patches and one that no longer applies.

The worst step for me is, by far, the git-am step. Resolving patch
conflicts is painful because you have to manually apply the patch,
then remember to git add all the files modified by the patch, etc.

I don't know how to use git to properly back out a patch that was made at some time in the past. Disaster management in particular has left me to backup at strategic points. On these older PCs, restore operations can be much faster than git recovery attempts.

`git am` is hard because that diagnostic "Patch does not apply" is not helpful, and the --ignore-whitespace option can cause trouble very quickly.

Any patches that don't apply by `git am` are reduced from E-mail to ordinary diffs and sent through `git apply`. If that doesn't work, they go through patch; vimdiff is used to help splice the patches in by hand. `git add` is then used to add the files.

It'd be really cool if guilt could do the import directly from the
mbox file without applying the patches, so the normal guilt
force-push-fix-and-refresh method of solving patch conflicts could
be used instead of git-am.

/me wonders if #jeffpc is listening here....

Great job on a fine patchset so far, and good luck!

Keep the bug reports rolling in, Michael. ;)

Thanks!  It's all good fun :-)


[ 6188.126012] XFS: Assertion failed: first <= last && last <
BBTOB(bp->b_length), file: fs/xfs/xfs_trans_buf.c, line: 569

Hmmm - that seems familiar - I thought I'd already fixed a bug like
that previously...

You may have fixed it already. If there's a patch, either I don't have it, or it's stuck on my main xfstests PC at home. Was this the issue that was triggered easily by xfstests xfs/017?

[ 6188.147632]  [<c11c6d67>] xfs_trans_log_buf+0x64/0x11b
[ 6188.147632]  [<c11a0653>] xfs_dir2_data_log_unused+0x7b/0x83
[ 6188.147632]  [<c11a0e45>] xfs_dir2_data_use_free+0x1bf/0x41a
[ 6188.147632]  [<c11a308b>] xfs_dir2_leaf_addname+0x307/0x6f2
[ 6188.147632]  [<c119d32f>] xfs_dir_createname+0x113/0x129
[ 6188.147632]  [<c1174633>] xfs_create+0x3e0/0x4fb

I'll look into that further - it's a different problem to what I'm
stuck on at the moment...



No worries. It will take a while to compile an initial xfstests report with CRC-enabled filesystems.

Thanks again!


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