On 2016-08-15 08:19, Martin wrote:
I'm not sure what Arch does any differently to their kernels from
kernel.org kernels. But bugzilla.kernel.org offers a Mainline and
Fedora drop down for identifying the kernel source tree.

IIRC, they're pretty close to mainline kernels.  I don't think they have any
patches in the filesystem or block layer code at least, but I may be wrong,
it's been a long time since I looked at an Arch kernel.

Perhaps I should use Arch then, as Fedora rawhide kernel wouldn't boot
on my hw, so I am running the stock Fedora 24 kernel right now for the
tests...

If I want to compile a mainline kernel. Are there anything I need to
tune?


Fedora kernels do not have these options set.

# CONFIG_BTRFS_FS_CHECK_INTEGRITY is not set
# CONFIG_BTRFS_FS_RUN_SANITY_TESTS is not set
# CONFIG_BTRFS_DEBUG is not set
# CONFIG_BTRFS_ASSERT is not set

The sanity and integrity tests are both compile time and mount time
options, i.e. it has to be compiled enabled for the mount option to do
anything. I can't recall any thread where a developer asked a user to
set any of these options for testing though.

FWIW, I actually have the integrity checking code built in on most kernels I
build.  I don't often use it, but it has near zero overhead when not
enabled, and it's helped me track down lower-level storage configuration
issues on occasion.

I'll give that a shot tomorrow.

When I do the tests, how do I log the info you would like to see, if I
find a bug?


bugzilla.kernel.org for tracking, and then reference the URL for the
bug with a summary in an email to list is how I usually do it. The
main thing is going to be the exact reproduce steps. It's also better,
I think, to have complete dmesg (or journalctl -k) attached to the bug
report because not all problems are directly related to Btrfs, they
can have contributing factors elsewhere. And various MTAs, or more
commonly MUAs, have a tendancy to wrap such wide text as found in
kernel or journald messages.

Aside from kernel messages, the other general stuff you want to have is:
1. Kernel version and userspace tools version (`uname -a` and `btrfs
--version`)
2. Any underlying storage configuration if it's not just plain a SSD/HDD or
partitions (for example, usage of dm-crypt, LVM, mdadm, and similar things).
3. Output from `btrfs filesystem show` (this can be trimmed to the
filesystem that's having the issue).
4. If you can still mount the filesystem, `btrfs filesystem df` output can
be helpful.
5. If you can't mount the filesystem, output from `btrfs check` run without
any options will usually be asked for.

I have now had the first crash, can you take a look if I have provided
the needed info?

https://bugzilla.kernel.org/show_bug.cgi?id=153141

How long should I keep the host untouched? Or is all interesting idea provided?

Looking at the kernel log itself, you've got a ton of write errors on /dev/sdap. I would suggest checking that particular disk with smartctl, and possibly checking the other hardware involved (the storage controller and cabling).

I would kind of expect BTRFS to crash with that many write errors regardless of what profile is being used, but we really should get better about reporting errors to user space in a sane way (making people dig through kernel logs to figure out their having issues like this is not particularly user friendly).
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