Ceph » CephFS

What kernel version are you running this on? Is this something easily reproducible, or does it take a while?

There are two different modes when you do a setxattr or removexattr:

If you have the exclusive xattr cap (aka Xx) then the set or removexattr will be done locally and the cap dirtied so the new xattr blob would eventually get sent to the MDS. If you don't have the Xx cap, then it does a synchronous SETXATTR call to the MDS.

So, it's one (or possibly a combination) of three things:

1. the client did the change locally and never flushed the updated xattr blob to the MDS for some reason
2. the client did flush the blob to the MDS, but it dropped the update onto the floor or reverted it for some reason
3. the client did a synchronous SETXATTR call and it didn't stick for some reason

Given that you saw the change in a getxattr after it happened, #3 seems less likely than the others.

Hi Jeff,

thanks for looking into this!

Jeff Layton wrote:

What kernel version are you running this on?

1. uname -r
   3.10.0-1062.18.1.el7.x86_64

Is this something easily reproducible, or does it take a while?

It's reliably reproducible.

There are two different modes when you do a setxattr or removexattr:

If you have the exclusive xattr cap (aka Xx) then the set or removexattr will be done locally and the cap dirtied so the new xattr blob would eventually get sent to the MDS. If you don't have the Xx cap, then it does a synchronous SETXATTR call to the MDS.

So, it's one (or possibly a combination) of three things:

1. the client did the change locally and never flushed the updated xattr blob to the MDS for some reason
2. the client did flush the blob to the MDS, but it dropped the update onto the floor or reverted it for some reason
3. the client did a synchronous SETXATTR call and it didn't stick for some reason

Given that you saw the change in a getxattr after it happened, #3 seems less likely than the others.

Any suggestion how to diagnose this further?

Thanks!
-slow

Ralph Böhme wrote:

What kernel version are you running this on?

1. uname -r
   3.10.0-1062.18.1.el7.x86_64

Ok. RHEL7's kcephfs client is quite old. It's possible that this is something fixed in a more recent kernel version. It might be good to test something closer to mainline (a RHEL8.4-ish kernel is probably close enough here too).

It's reliably reproducible.

Good. Is it reproducible without samba? A standalone reproducer would be nice if possible.

There are two different modes when you do a setxattr or removexattr:

If you have the exclusive xattr cap (aka Xx) then the set or removexattr will be done locally and the cap dirtied so the new xattr blob would eventually get sent to the MDS. If you don't have the Xx cap, then it does a synchronous SETXATTR call to the MDS.

So, it's one (or possibly a combination) of three things:

1. the client did the change locally and never flushed the updated xattr blob to the MDS for some reason
2. the client did flush the blob to the MDS, but it dropped the update onto the floor or reverted it for some reason
3. the client did a synchronous SETXATTR call and it didn't stick for some reason

Given that you saw the change in a getxattr after it happened, #3 seems less likely than the others.

Any suggestion how to diagnose this further?

I think trying to first reproduce this on a newer kernel would be the best thing. That would tell us whether we're looking at something that is still broken upstream or whether it's already fixed. Depending on the results of that, we'll need to do more to track down the actual bug, of course.

Jeff Layton wrote:

Ok. RHEL7's kcephfs client is quite old. It's possible that this is something fixed in a more recent kernel version. It might be good to test something closer to mainline (a RHEL8.4-ish kernel is probably close enough here too).

Ok. Will try to get some systems with newer kernels and see if the problems reproduces there.

Is it reproducible without samba? A standalone reproducer would be nice if possible.

If it still reproduces on newer kernel I'll prepare a simple program that repeats the pattern.

Thanks!
-slow

Ralph, ping? Were you ever able to determine whether this was fixed in later kernels?

Jeff Layton wrote:

Ralph, ping? Were you ever able to determine whether this was fixed in later kernels?

At first the problem seemed to have been solved after updating to newer kernel and ceph versions. But then a few days later it came back, worse then before. I'm going to work on trying to reproduce this with a local simple test program in the next days.

Ralph Böhme wrote:

I'm going to work on trying to reproduce this with a local simple test program in the next days.

No luck. :/ I tried several time with a C program modelled closely after the strace I have from an smbd where at the end, after a few hours of waiting, the "xattr returns from the dead" problem was seen.

Current versions:

Ceph Server: 14.2.21
Ceph Client: # uname -r -> 4.18.0-310.el8.x86_64

The servers will b updated in a few months, I'll report back if anything changes then.

Hi Jeff!

Just wanted to let you know that this issue is still relevant and severe with more recent versions of both Ceph and Linux. We run Ceph 16.2.11 and Linux 5.13.19 with samba 4.17.6, on metadata-servers we run Linux 6.2.9. We can easily reproduce this issue by copying a handfull (50+) of files from a macOS workstation to a samba share with vfs_fruit. About 5% of files have the brokMACS xattr sequence still set after copying is finished.

Another interesting find is that it only seems to affect files that have a known format to macOS like pdf, png, wav, txt etc. If I copy a set of files that have no or unknown extension the brokMACS sequence is not seen on those files.

See recent discussion on the samba mailing list: https://lists.samba.org/archive/samba/2023-May/245150.html

Hi Jeff,

we're also affected by this issue and can confirm the behaviour Thomas described.

Versions here:

Ceph 17.2.6 with kernel 5.10.0-23-amd64 on Debian Bullseye
Samba 4.18.2 (sernet packages) with kernel 5.10.0-23-amd64 on Debian Bullseye

Would be great if this issue can be reopened and investigate further.

Thanks!

Tobias Hachmer wrote:

Hi Jeff,

we're also affected by this issue and can confirm the behaviour Thomas described.

Versions here:

Ceph 17.2.6 with kernel 5.10.0-23-amd64 on Debian Bullseye
Samba 4.18.2 (sernet packages) with kernel 5.10.0-23-amd64 on Debian Bullseye

Would be great if this issue can be reopened and investigate further.

Thanks!

Hi Tobias

Could you reproduce it by enabling the mds debug logs ?

For the MDS daemons, set:

debug_mds = 25
debug_ms = 1

And also if possible please enable the kclient debug log:

echo "module ceph +p" | sudo tee /sys/kernel/debug/dynamic_debug/control

If you can provide the above logs I can find the root cause soon.

Thanks
- Xiubo

Hi Xiubo,

thanks for taking care of this issue and the debug info.

We have here only a production system. Can you please describe the impact of the two debug options a bit more in detail. Will this lead to higher/heavy load of the MDS, decreased performance, big load of log file, etc.?

Thanks
Tobias

Tobias Hachmer wrote:

Hi Xiubo,

thanks for taking care of this issue and the debug info.

We have here only a production system. Can you please describe the impact of the two debug options a bit more in detail. Will this lead to higher/heavy load of the MDS, decreased performance, big load of log file, etc.?

For production system this certainly will lead to heavy load and perf issues in both kclient and MDSs.

But if you can reproduce this always, then this should be okay IMO, you can just catch the logs and then disable the debug logs in both side after that.

Thanks
Tobias

Hello,

I've come across this Ceph issue and noticed it hasn't been updated in 9 months. I aim to shed light on this bug again, hoping to contribute to finding a resolution. Please let me know what information I can provide to expedite the process. Thank you.

Austin Axworthy wrote:

Hello,

I've come across this Ceph issue and noticed it hasn't been updated in 9 months. I aim to shed light on this bug again, hoping to contribute to finding a resolution. Please let me know what information I can provide to expedite the process. Thank you.

Hi Austin,

If you can also reproduce it, then could you help provide the debug logs as I mentioned in comment#12 ?

Thanks.

We are currently working on recreating this issue internally as this was a customer cluster that was having the issue Austin mentioned.

As a workaround to resolve this issue for our customer, we added "vfs_streams_depot" to our SMB shares so that it does not put the attr on the individual files and instead makes a single depot file which contains them all

Once I have recreated this issue I will be able to provide the logs from comment #12

Matthew Hutchinson wrote:

We are currently working on recreating this issue internally as this was a customer cluster that was having the issue Austin mentioned.

As a workaround to resolve this issue for our customer, we added "vfs_streams_depot" to our SMB shares so that it does not put the attr on the individual files and instead makes a single depot file which contains them all

Once I have recreated this issue I will be able to provide the logs from comment #12

Sounds good. Thanks!

Is there anything in the logs you saw that could be causing this issue? I am eager to get this resolved for all of our MAC clients using cephfs

Matthew Hutchinson wrote:

Is there anything in the logs you saw that could be causing this issue? I am eager to get this resolved for all of our MAC clients using cephfs

Sorry, I missed you last comments, I will check it tomorrow.

Matthew Hutchinson wrote:

Is there anything in the logs you saw that could be causing this issue? I am eager to get this resolved for all of our MAC clients using cephfs

BTW, which xattr you were using ? Still user.DosStream.AFP_AfpInfo ? Why I couldn't see any logs in the log files you uploaded ?

The mds log file is too short and I didn't see any logs about this.

Matthew Hutchinson wrote:

We are currently using "streams_xattr" "acl_xattr"

Hi Mathew,

BTW, do you have the full logs or you can just upload it somewhere I can access? This is still the same. I need to whole logs from beginning you to remove the xattr to when this happens.

And if possible if you could enable the kernel ceph's debug logs will be better.

Thanks

Those MDs logs would be everything. they are from the moment I built the MDS services until you requested the logs which should have the issue.

This is a VM cluster so I can spin it back up and gather any additional info you may need

HI, Can I get an update on this?