26 Mar
2020
26 Mar
'20
1:48 p.m.
Some time ago I made a surprising observation. I reorganised a directory structure and
needed to move a folder one level up with a command like
mv A/B/ B
B contained something like 9TB in very large files. To my surprise, this command
didn't return for a couple of minutes and I started to look what was going on. What I
discovered was, that the mv command actually performed a full copy with a subsequent
remove. I had to wait for several hours for the move to complete.
I tried to reproduce this today to collect further information. However, this behaviour
seems not reproducible. No matter what I try, mv completes almost instantly.
I was running the original mv on mimic 13.2.2 and retried now with mimic 13.2.8. In
addition, there was an OS upgrade from Centos 7.6 to 7.7. I'm using the kernel-ml
versions (5.xxx). Only one cephfs mount was present at all times.
My questions are:
1) Was there a change from 13.2.2 to 13.2.8 explaining this?
2) Are there (rare) conditions under which an mv on cephfs becomes a cp+rm?
3) Am I seeing ghosts?
Thanks for clues and best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
26 Mar
26 Mar
3:12 p.m.
On Thu, Mar 26, 2020 at 5:49 AM Frank Schilder <frans(a)dtu.dk> wrote:
Some time ago I made a surprising observation. I reorganised a directory structure and
needed to move a folder one level up with a command like
mv A/B/ B
B contained something like 9TB in very large files. To my surprise, this command
didn't return for a couple of minutes and I started to look what was going on. What I
discovered was, that the mv command actually performed a full copy with a subsequent
remove. I had to wait for several hours for the move to complete.
I tried to reproduce this today to collect further information. However, this behaviour
seems not reproducible. No matter what I try, mv completes almost instantly.
I was running the original mv on mimic 13.2.2 and retried now with mimic 13.2.8. In
addition, there was an OS upgrade from Centos 7.6 to 7.7. I'm using the kernel-ml
versions (5.xxx). Only one cephfs mount was present at all times.
My questions are:
1) Was there a change from 13.2.2 to 13.2.8 explaining this?
No.
2) Are there (rare) conditions under which an mv on
cephfs becomes a cp+rm?
Not as part of CephFS.
3) Am I seeing ghosts?
The only way I can imagine this happening is if you had separate
CephFS mounts for cephfs/A/B and cephfs/ and you did the move between
them, instead of within the cephfs/ mount. :/
-Greg
Thanks for clues and best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io
3:17 p.m.
Is there is a possibility that there was a quota involved? I've seen
moves between quota zones to cause a copy then delete.
--
Adam
On Thu, Mar 26, 2020 at 9:14 AM Gregory Farnum <gfarnum(a)redhat.com> wrote:
>
> On Thu, Mar 26, 2020 at 5:49 AM Frank Schilder <frans(a)dtu.dk> wrote:
> >
> > Some time ago I made a surprising observation. I reorganised a directory
structure and needed to move a folder one level up with a command like
> >
> > mv A/B/ B
> >
> > B contained something like 9TB in very large files. To my surprise, this command
didn't return for a couple of minutes and I started to look what was going on. What I
discovered was, that the mv command actually performed a full copy with a subsequent
remove. I had to wait for several hours for the move to complete.
> >
> > I tried to reproduce this today to collect further information. However, this
behaviour seems not reproducible. No matter what I try, mv completes almost instantly.
> >
> > I was running the original mv on mimic 13.2.2 and retried now with mimic 13.2.8.
In addition, there was an OS upgrade from Centos 7.6 to 7.7. I'm using the kernel-ml
versions (5.xxx). Only one cephfs mount was present at all times.
> >
> > My questions are:
> >
> > 1) Was there a change from 13.2.2 to 13.2.8 explaining this?
>
> No.
>
> > 2) Are there (rare) conditions under which an mv on cephfs becomes a cp+rm?
>
> Not as part of CephFS.
>
> > 3) Am I seeing ghosts?
>
> The only way I can imagine this happening is if you had separate
> CephFS mounts for cephfs/A/B and cephfs/ and you did the move between
> them, instead of within the cephfs/ mount. :/
> -Greg
>
> >
> > Thanks for clues and best regards,
> >
> > =================
> > Frank Schilder
> > AIT Risø Campus
> > Bygning 109, rum S14
> > _______________________________________________
> > ceph-users mailing list -- ceph-users(a)ceph.io
> > To unsubscribe send an email to ceph-users-leave(a)ceph.io
> >
> _______________________________________________
> ceph-users mailing list -- ceph-users(a)ceph.io
> To unsubscribe send an email to ceph-users-leave(a)ceph.io
3:20 p.m.
I was wondering that but at least in the userspace client the quotas
will just throw EXDEV or EDQUOT if it will exceed quotas...
...and EXDEV might trigger the kernel to do a copy-and-delete, I
guess? Not sure.
On Thu, Mar 26, 2020 at 7:18 AM Adam Tygart <mozes(a)ksu.edu> wrote:
Is there is a possibility that there was a quota involved? I've seen
moves between quota zones to cause a copy then delete.
--
Adam
On Thu, Mar 26, 2020 at 9:14 AM Gregory Farnum <gfarnum(a)redhat.com> wrote:
On Thu, Mar 26, 2020 at 5:49 AM Frank Schilder <frans(a)dtu.dk> wrote:
Some time ago I made a surprising observation. I reorganised a directory structure and
needed to move a folder one level up with a command like
mv A/B/ B
B contained something like 9TB in very large files. To my surprise, this command
didn't return for a couple of minutes and I started to look what was going on. What I
discovered was, that the mv command actually performed a full copy with a subsequent
remove. I had to wait for several hours for the move to complete.
I tried to reproduce this today to collect further information. However, this behaviour
seems not reproducible. No matter what I try, mv completes almost instantly.
I was running the original mv on mimic 13.2.2 and retried now with mimic 13.2.8. In
addition, there was an OS upgrade from Centos 7.6 to 7.7. I'm using the kernel-ml
versions (5.xxx). Only one cephfs mount was present at all times.
My questions are:
1) Was there a change from 13.2.2 to 13.2.8 explaining this?
No.
2) Are there (rare) conditions under which an mv
on cephfs becomes a cp+rm?
Not as part of CephFS.
3) Am I seeing ghosts?
The only way I can imagine this happening is if you had separate
CephFS mounts for cephfs/A/B and cephfs/ and you did the move between
them, instead of within the cephfs/ mount. :/
-Greg
Thanks for clues and best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io
4:35 p.m.
Dear all, thanks for the hints. I was afraid I see ghosts.
Yes, we have quotas on many directories. I'm not entirely sure if there were different
quotas involved. I believe it was set only on the highest level, but now that you mention
it ...
I will try with quotas again, didn't include this in my scenario.
This information is really important, because it will affect how I as an admin can move
data between folders with quotas on them, which are typically used for sub-directory
mounts. For a user this would look like a magical move between file systems.
I will get back. Thanks!
Best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
________________________________________
From: Gregory Farnum <gfarnum(a)redhat.com>
Sent: 26 March 2020 15:20:51
To: Beocat KSU
Cc: ceph-users; Frank Schilder
Subject: Re: [ceph-users] Re: Move on cephfs not O(1)?
I was wondering that but at least in the userspace client the quotas
will just throw EXDEV or EDQUOT if it will exceed quotas...
...and EXDEV might trigger the kernel to do a copy-and-delete, I
guess? Not sure.
On Thu, Mar 26, 2020 at 7:18 AM Adam Tygart <mozes(a)ksu.edu> wrote:
Is there is a possibility that there was a quota involved? I've seen
moves between quota zones to cause a copy then delete.
--
Adam
On Thu, Mar 26, 2020 at 9:14 AM Gregory Farnum <gfarnum(a)redhat.com> wrote:
On Thu, Mar 26, 2020 at 5:49 AM Frank Schilder <frans(a)dtu.dk> wrote:
Some time ago I made a surprising observation. I reorganised a directory structure and
needed to move a folder one level up with a command like
mv A/B/ B
B contained something like 9TB in very large files. To my surprise, this command
didn't return for a couple of minutes and I started to look what was going on. What I
discovered was, that the mv command actually performed a full copy with a subsequent
remove. I had to wait for several hours for the move to complete.
I tried to reproduce this today to collect further information. However, this behaviour
seems not reproducible. No matter what I try, mv completes almost instantly.
I was running the original mv on mimic 13.2.2 and retried now with mimic 13.2.8. In
addition, there was an OS upgrade from Centos 7.6 to 7.7. I'm using the kernel-ml
versions (5.xxx). Only one cephfs mount was present at all times.
My questions are:
1) Was there a change from 13.2.2 to 13.2.8 explaining this?
No.
2) Are there (rare) conditions under which an mv
on cephfs becomes a cp+rm?
Not as part of CephFS.
3) Am I seeing ghosts?
The only way I can imagine this happening is if you had separate
CephFS mounts for cephfs/A/B and cephfs/ and you did the move between
them, instead of within the cephfs/ mount. :/
-Greg
Thanks for clues and best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io
5:13 p.m.
Dear all,
yes, this is it, quotas. In the structure A/B/ there was a quota set on A. Hence, B was
moved out of this zone and this does indeed change mv to be a cp+rm.
The obvious follow-up. What is the procedure for properly moving data as an administrator?
Do I really need to unset quotas, do the move and set quotas back again?
Best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
________________________________________
From: Frank Schilder <frans(a)dtu.dk>
Sent: 26 March 2020 16:35:07
To: Gregory Farnum; Beocat KSU
Cc: ceph-users
Subject: [ceph-users] Re: Move on cephfs not O(1)?
Dear all, thanks for the hints. I was afraid I see ghosts.
Yes, we have quotas on many directories. I'm not entirely sure if there were different
quotas involved. I believe it was set only on the highest level, but now that you mention
it ...
I will try with quotas again, didn't include this in my scenario.
This information is really important, because it will affect how I as an admin can move
data between folders with quotas on them, which are typically used for sub-directory
mounts. For a user this would look like a magical move between file systems.
I will get back. Thanks!
Best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
________________________________________
From: Gregory Farnum <gfarnum(a)redhat.com>
Sent: 26 March 2020 15:20:51
To: Beocat KSU
Cc: ceph-users; Frank Schilder
Subject: Re: [ceph-users] Re: Move on cephfs not O(1)?
I was wondering that but at least in the userspace client the quotas
will just throw EXDEV or EDQUOT if it will exceed quotas...
...and EXDEV might trigger the kernel to do a copy-and-delete, I
guess? Not sure.
On Thu, Mar 26, 2020 at 7:18 AM Adam Tygart <mozes(a)ksu.edu> wrote:
Is there is a possibility that there was a quota involved? I've seen
moves between quota zones to cause a copy then delete.
--
Adam
On Thu, Mar 26, 2020 at 9:14 AM Gregory Farnum <gfarnum(a)redhat.com> wrote:
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io
On Thu, Mar 26, 2020 at 5:49 AM Frank Schilder <frans(a)dtu.dk> wrote:
Some time ago I made a surprising observation. I reorganised a directory structure and
needed to move a folder one level up with a command like
mv A/B/ B
B contained something like 9TB in very large files. To my surprise, this command
didn't return for a couple of minutes and I started to look what was going on. What I
discovered was, that the mv command actually performed a full copy with a subsequent
remove. I had to wait for several hours for the move to complete.
I tried to reproduce this today to collect further information. However, this behaviour
seems not reproducible. No matter what I try, mv completes almost instantly.
I was running the original mv on mimic 13.2.2 and retried now with mimic 13.2.8. In
addition, there was an OS upgrade from Centos 7.6 to 7.7. I'm using the kernel-ml
versions (5.xxx). Only one cephfs mount was present at all times.
My questions are:
1) Was there a change from 13.2.2 to 13.2.8 explaining this?
No.
2) Are there (rare) conditions under which an mv
on cephfs becomes a cp+rm?
Not as part of CephFS.
3) Am I seeing ghosts?
The only way I can imagine this happening is if you had separate
CephFS mounts for cephfs/A/B and cephfs/ and you did the move between
them, instead of within the cephfs/ mount. :/
-Greg
Thanks for clues and best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io
6:32 p.m.
On Thu, Mar 26, 2020 at 9:13 AM Frank Schilder <frans(a)dtu.dk> wrote:
Dear all,
yes, this is it, quotas. In the structure A/B/ there was a quota set on A. Hence, B was
moved out of this zone and this does indeed change mv to be a cp+rm.
The obvious follow-up. What is the procedure for properly moving data as an
administrator? Do I really need to unset quotas, do the move and set quotas back again?
Ah-ha, this is a difference between the userspace and kernel clients.
:( The kernel client always returns EXDEV if crossing "quota realms"
(different quota roots). I'm not sure why it behaves that way as
userspace is different:
* If fhere is a quota in the target directory, and
* If the target directory's existing data, plus the file(s) being
moved, exceed the target directory's quota,
then userspace returns EXDEV/EDQUOT. This seems like the right kernel
behavior as well...
Jeff, is that a known issue for some reason? Should we make a new bug? :)
-Greg
Best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
________________________________________
From: Frank Schilder <frans(a)dtu.dk>
Sent: 26 March 2020 16:35:07
To: Gregory Farnum; Beocat KSU
Cc: ceph-users
Subject: [ceph-users] Re: Move on cephfs not O(1)?
Dear all, thanks for the hints. I was afraid I see ghosts.
Yes, we have quotas on many directories. I'm not entirely sure if there were
different quotas involved. I believe it was set only on the highest level, but now that
you mention it ...
I will try with quotas again, didn't include this in my scenario.
This information is really important, because it will affect how I as an admin can move
data between folders with quotas on them, which are typically used for sub-directory
mounts. For a user this would look like a magical move between file systems.
I will get back. Thanks!
Best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
________________________________________
From: Gregory Farnum <gfarnum(a)redhat.com>
Sent: 26 March 2020 15:20:51
To: Beocat KSU
Cc: ceph-users; Frank Schilder
Subject: Re: [ceph-users] Re: Move on cephfs not O(1)?
I was wondering that but at least in the userspace client the quotas
will just throw EXDEV or EDQUOT if it will exceed quotas...
...and EXDEV might trigger the kernel to do a copy-and-delete, I
guess? Not sure.
On Thu, Mar 26, 2020 at 7:18 AM Adam Tygart <mozes(a)ksu.edu> wrote:
Is there is a possibility that there was a quota involved? I've seen
moves between quota zones to cause a copy then delete.
--
Adam
On Thu, Mar 26, 2020 at 9:14 AM Gregory Farnum <gfarnum(a)redhat.com> wrote:
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io
On Thu, Mar 26, 2020 at 5:49 AM Frank Schilder <frans(a)dtu.dk> wrote:
Some time ago I made a surprising observation. I reorganised a directory structure and
needed to move a folder one level up with a command like
mv A/B/ B
B contained something like 9TB in very large files. To my surprise, this command
didn't return for a couple of minutes and I started to look what was going on. What I
discovered was, that the mv command actually performed a full copy with a subsequent
remove. I had to wait for several hours for the move to complete.
I tried to reproduce this today to collect further information. However, this behaviour
seems not reproducible. No matter what I try, mv completes almost instantly.
I was running the original mv on mimic 13.2.2 and retried now with mimic 13.2.8. In
addition, there was an OS upgrade from Centos 7.6 to 7.7. I'm using the kernel-ml
versions (5.xxx). Only one cephfs mount was present at all times.
My questions are:
1) Was there a change from 13.2.2 to 13.2.8 explaining this?
No.
2) Are there (rare) conditions under which an mv
on cephfs becomes a cp+rm?
Not as part of CephFS.
3) Am I seeing ghosts?
The only way I can imagine this happening is if you had separate
CephFS mounts for cephfs/A/B and cephfs/ and you did the move between
them, instead of within the cephfs/ mount. :/
-Greg
Thanks for clues and best regards,
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io
_______________________________________________
ceph-users mailing list -- ceph-users(a)ceph.io
To unsubscribe send an email to ceph-users-leave(a)ceph.io 
27 Mar
27 Mar
12:36 p.m.
On Thu, 2020-03-26 at 10:32 -0700, Gregory Farnum wrote:
On Thu, Mar 26, 2020 at 9:13 AM Frank Schilder
<frans(a)dtu.dk> wrote:
(cc'ing Luis since he wrote cafe21a4fb3075, which added this check)
In ceph_rename, we have this, which is probably what you're hitting:
/* don't allow cross-quota renames */
if ((old_dir != new_dir) &&
(!ceph_quota_is_same_realm(old_dir, new_dir)))
return -EXDEV;
That does seem to just check whether the realms are the same and doesn't
actually check the space in them.
I haven't studied this in detail, but it may be hard to ensure that we
won't exceed the quota in a race-free way. How do you ensure that
another thread doesn't do something that would exceed the quota just as
you issue the rename request?
This is fairly trivial in the userland client since it does everything
under the BCM (Big Client Mutex), but won't be in the kernel client.
Opening a bug for this won't hurt, but it may not be simple to
implement.
--
Jeff Layton <jlayton(a)redhat.com>
Dear all,
yes, this is it, quotas. In the structure A/B/ there was a quota set on A. Hence, B was
moved out of this zone and this does indeed change mv to be a cp+rm.
The obvious follow-up. What is the procedure for properly moving data as an
administrator? Do I really need to unset quotas, do the move and set quotas back again?
Ah-ha, this is a difference between the userspace and kernel clients.
:( The kernel client always returns EXDEV if crossing "quota realms"
(different quota roots). I'm not sure why it behaves that way as
userspace is different:
* If fhere is a quota in the target directory, and
* If the target directory's existing data, plus the file(s) being
moved, exceed the target directory's quota,
then userspace returns EXDEV/EDQUOT. This seems like the right kernel
behavior as well...
Jeff, is that a known issue for some reason? Should we make a new bug? :)
3:34 p.m.
On Fri, 2020-03-27 at 07:36 -0400, Jeff Layton wrote:
On Thu, 2020-03-26 at 10:32 -0700, Gregory Farnum
wrote:
Ok, I gave it a harder look and it doesn't look too bad, given that
quotas are sort of "sloppy" anyway. We could just do a check that we
won't exceed quota on the destination directory. The catch is that there
may be other details to deal with too in moving an existing inode under
a different snaprealm.
You're welcome to open a tracker bug for this, but I'm not sure who will
take on that project and when.
Thanks,
--
Jeff Layton <jlayton(a)redhat.com>
On Thu, Mar 26, 2020 at 9:13 AM Frank Schilder
<frans(a)dtu.dk> wrote:
(cc'ing Luis since he wrote cafe21a4fb3075, which added this check)
In ceph_rename, we have this, which is probably what you're hitting:
/* don't allow cross-quota renames */
if ((old_dir != new_dir) &&
(!ceph_quota_is_same_realm(old_dir, new_dir)))
return -EXDEV;
That does seem to just check whether the realms are the same and doesn't
actually check the space in them.
I haven't studied this in detail, but it may be hard to ensure that we
won't exceed the quota in a race-free way. How do you ensure that
another thread doesn't do something that would exceed the quota just as
you issue the rename request?
This is fairly trivial in the userland client since it does everything
under the BCM (Big Client Mutex), but won't be in the kernel client.
Opening a bug for this won't hurt, but it may not be simple to
implement. Dear all,
yes, this is it, quotas. In the structure A/B/ there was a quota set on A. Hence, B was
moved out of this zone and this does indeed change mv to be a cp+rm.
The obvious follow-up. What is the procedure for properly moving data as an
administrator? Do I really need to unset quotas, do the move and set quotas back again?
Ah-ha, this is a difference between the userspace and kernel clients.
:( The kernel client always returns EXDEV if crossing "quota realms"
(different quota roots). I'm not sure why it behaves that way as
userspace is different:
* If fhere is a quota in the target directory, and
* If the target directory's existing data, plus the file(s) being
moved, exceed the target directory's quota,
then userspace returns EXDEV/EDQUOT. This seems like the right kernel
behavior as well...
Jeff, is that a known issue for some reason? Should we make a new bug? :)
9:18 p.m.
Made a ticket in the Linux Kernel Client tracker:
https://tracker.ceph.com/issues/44791
I naively don't think this should be very complicated at all, except
that I recall hearing something about locking issues with quota realms
in the kclient? But the userspace client definitely doesn't have to do
anything tricky with moving things, it's pretty much a normal move
with some glue to point at a different quota realm.
-Greg
On Fri, Mar 27, 2020 at 7:34 AM Jeff Layton <jlayton(a)redhat.com> wrote:
On Fri, 2020-03-27 at 07:36 -0400, Jeff Layton wrote:
On Thu, 2020-03-26 at 10:32 -0700, Gregory Farnum
wrote:
Ok, I gave it a harder look and it doesn't look too bad, given that
quotas are sort of "sloppy" anyway. We could just do a check that we
won't exceed quota on the destination directory. The catch is that there
may be other details to deal with too in moving an existing inode under
a different snaprealm.
You're welcome to open a tracker bug for this, but I'm not sure who will
take on that project and when.
Thanks,
--
Jeff Layton <jlayton(a)redhat.com>
On Thu, Mar 26, 2020 at 9:13 AM Frank Schilder
<frans(a)dtu.dk> wrote:
(cc'ing Luis since he wrote cafe21a4fb3075, which added this check)
In ceph_rename, we have this, which is probably what you're hitting:
/* don't allow cross-quota renames */
if ((old_dir != new_dir) &&
(!ceph_quota_is_same_realm(old_dir, new_dir)))
return -EXDEV;
That does seem to just check whether the realms are the same and doesn't
actually check the space in them.
I haven't studied this in detail, but it may be hard to ensure that we
won't exceed the quota in a race-free way. How do you ensure that
another thread doesn't do something that would exceed the quota just as
you issue the rename request?
This is fairly trivial in the userland client since it does everything
under the BCM (Big Client Mutex), but won't be in the kernel client.
Opening a bug for this won't hurt, but it may not be simple to
implement. Dear all,
yes, this is it, quotas. In the structure A/B/ there was a quota set on A. Hence, B was
moved out of this zone and this does indeed change mv to be a cp+rm.
The obvious follow-up. What is the procedure for properly moving data as an
administrator? Do I really need to unset quotas, do the move and set quotas back again?
Ah-ha, this is a difference between the userspace and kernel clients.
:( The kernel client always returns EXDEV if crossing "quota realms"
(different quota roots). I'm not sure why it behaves that way as
userspace is different:
* If fhere is a quota in the target directory, and
* If the target directory's existing data, plus the file(s) being
moved, exceed the target directory's quota,
then userspace returns EXDEV/EDQUOT. This seems like the right kernel
behavior as well...
Jeff, is that a known issue for some reason? Should we make a new bug? :)
9:22 p.m.
Thanks a lot! Have a good weekend.
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
________________________________________
From: Gregory Farnum <gfarnum(a)redhat.com>
Sent: 27 March 2020 21:18:37
To: Jeff Layton
Cc: Frank Schilder; Zheng Yan; ceph-users; Luis Henriques
Subject: Re: [ceph-users] Re: Move on cephfs not O(1)?
Made a ticket in the Linux Kernel Client tracker:
https://tracker.ceph.com/issues/44791
I naively don't think this should be very complicated at all, except
that I recall hearing something about locking issues with quota realms
in the kclient? But the userspace client definitely doesn't have to do
anything tricky with moving things, it's pretty much a normal move
with some glue to point at a different quota realm.
-Greg
On Fri, Mar 27, 2020 at 7:34 AM Jeff Layton <jlayton(a)redhat.com> wrote:
On Fri, 2020-03-27 at 07:36 -0400, Jeff Layton wrote:
On Thu, 2020-03-26 at 10:32 -0700, Gregory Farnum
wrote:
Ok, I gave it a harder look and it doesn't look too bad, given that
quotas are sort of "sloppy" anyway. We could just do a check that we
won't exceed quota on the destination directory. The catch is that there
may be other details to deal with too in moving an existing inode under
a different snaprealm.
You're welcome to open a tracker bug for this, but I'm not sure who will
take on that project and when.
Thanks,
--
Jeff Layton <jlayton(a)redhat.com>
On Thu, Mar 26, 2020 at 9:13 AM Frank Schilder
<frans(a)dtu.dk> wrote:
(cc'ing Luis since he wrote cafe21a4fb3075, which added this check)
In ceph_rename, we have this, which is probably what you're hitting:
/* don't allow cross-quota renames */
if ((old_dir != new_dir) &&
(!ceph_quota_is_same_realm(old_dir, new_dir)))
return -EXDEV;
That does seem to just check whether the realms are the same and doesn't
actually check the space in them.
I haven't studied this in detail, but it may be hard to ensure that we
won't exceed the quota in a race-free way. How do you ensure that
another thread doesn't do something that would exceed the quota just as
you issue the rename request?
This is fairly trivial in the userland client since it does everything
under the BCM (Big Client Mutex), but won't be in the kernel client.
Opening a bug for this won't hurt, but it may not be simple to
implement. Dear all,
yes, this is it, quotas. In the structure A/B/ there was a quota set on A. Hence, B was
moved out of this zone and this does indeed change mv to be a cp+rm.
The obvious follow-up. What is the procedure for properly moving data as an
administrator? Do I really need to unset quotas, do the move and set quotas back again?
Ah-ha, this is a difference between the userspace and kernel clients.
:( The kernel client always returns EXDEV if crossing "quota realms"
(different quota roots). I'm not sure why it behaves that way as
userspace is different:
* If fhere is a quota in the target directory, and
* If the target directory's existing data, plus the file(s) being
moved, exceed the target directory's quota,
then userspace returns EXDEV/EDQUOT. This seems like the right kernel
behavior as well...
Jeff, is that a known issue for some reason? Should we make a new bug? :)
30 Mar
30 Mar
12:13 p.m.
On Fri, Mar 27, 2020 at 07:36:15AM -0400, Jeff Layton wrote:
On Thu, 2020-03-26 at 10:32 -0700, Gregory Farnum
wrote:
(Sorry for the delay replying.)
So, I did a bit of digging (it has been a while since last time I looked
at this code) and the reason for this -EXDEV was to actually mimic the
code in the userspace client code (see bbfeaaea53f1 ("client: Forbid
moving files across quota trees")).
In the meantime, it seems like this restriction has been removed from the
userspace client in commit b8954e5734b3 ("client: optimize rename
operation under different quota root"). I'll try to have a look at this
in the next few days and see how this could be included in the kernel
client as well.
Cheers,
--
Luis
>
> I haven't studied this in detail, but it may be hard to ensure that we
> won't exceed the quota in a race-free way. How do you ensure that
> another thread doesn't do something that would exceed the quota just as
> you issue the rename request?
>
> This is fairly trivial in the userland client since it does everything
> under the BCM (Big Client Mutex), but won't be in the kernel client.
>
> Opening a bug for this won't hurt, but it may not be simple to
> implement.
> --
> Jeff Layton <jlayton(a)redhat.com>
> _______________________________________________
> ceph-users mailing list -- ceph-users(a)ceph.io
> To unsubscribe send an email to ceph-users-leave(a)ceph.io
On Thu, Mar 26, 2020 at 9:13 AM Frank Schilder
<frans(a)dtu.dk> wrote:
(cc'ing Luis since he wrote cafe21a4fb3075, which added this check)
In ceph_rename, we have this, which is probably what you're hitting:
/* don't allow cross-quota renames */
if ((old_dir != new_dir) &&
(!ceph_quota_is_same_realm(old_dir, new_dir)))
return -EXDEV;
That does seem to just check whether the realms are the same and doesn't
actually check the space in them. Dear all,
yes, this is it, quotas. In the structure A/B/ there was a quota set on A. Hence, B was
moved out of this zone and this does indeed change mv to be a cp+rm.
The obvious follow-up. What is the procedure for properly moving data as an
administrator? Do I really need to unset quotas, do the move and set quotas back again?
Ah-ha, this is a difference between the userspace and kernel clients.
:( The kernel client always returns EXDEV if crossing "quota realms"
(different quota roots). I'm not sure why it behaves that way as
userspace is different:
* If fhere is a quota in the target directory, and
* If the target directory's existing data, plus the file(s) being
moved, exceed the target directory's quota,
then userspace returns EXDEV/EDQUOT. This seems like the right kernel
behavior as well...
Jeff, is that a known issue for some reason? Should we make a new bug? :)
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participants (5)
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Gregory Farnum -
Jeff Layton -
Luis Henriques