[lustre-discuss] Project quota and odd mv behavior

[Andreas Dilger]

Looking at the strace output, it appears in all cases that the *directory*
rename is returning EXDEV, as it should be the case (to preserve the projid
for that directory tree).  In the XFS case, it is refusing to do the file
rename across projects also (returning EXDEV and forcing userspace to do the
file copy, which is very inefficient), while Lustre allows the file rename
to succeed (just reassinging the project quota usage).

In the lustre-mv-copy case, it appears that "mv" is not trying to rename the
file again after it creates the target directory, as it does in the lustre-mv
case.  Instead it just copies the file, which seems like a bug in "mv".

It looks like the renameat2() flags have not been implemented yet:
https://jira.whamcloud.com/browse/LU-12272 - RENAME_NOREPLACE 
https://jira.whamcloud.com/browse/LU-11557 - RENAME_EXCHANGE
https://jira.whamcloud.com/browse/LU-19720 - RENAME_WHITEOUT

Probably implementing RENAME_NOREPLACE support would be the most important
and useful flag, since "mv" is always trying this first.  RENAME_EXCHANGE
could be useful for some applications, while RENAME_WHITEOUT is for overlayfs.

Cheers, Andreas

> On Dec 17, 2025, at 05:54, Hans Henrik Happe via lustre-discuss <lustre-discuss at lists.lustre.org> wrote:
> 
> To be more specific:
> 
> Server: 
> - Lustre 2.15.7
> - Rocky Linux 8.10 (4.18.0-553.53.1.el8_10.x86_64)
> 
> Client:
> - Lustre 2.15.7, but same outcome on 2.15.5
> - Rocky Linux 9.6 (5.14.0-570.42.2.el9_6.x86_64)
> - glibc-2.34-168.el9_6.23.x86_64
> - coreutils-8.32-39.el9.x86_64
> 
> 
> 
> On 17/12/2025 13.22, Hans Henrik Happe via lustre-discuss wrote:
>> It's 2.15.7.
>> 
>> On 17/12/2025 03.36, Andreas Dilger wrote:
>>> There have definitely been some fixes in this area. 
>>> What version of Lustre are you running?
>>> 
>>> 
>>>> On Dec 16, 2025, at 07:39, Hans Henrik Happe via lustre-discuss <lustre-discuss at lists.lustre.org> wrote:
>>>> 
>>>> Hi,
>>>> 
>>>> 
>>>> It seems like the inherited project quota issue [1] with mv has been resolved with XFS in RHEL9. However, Lustre is a bit strange.
>>>> 
>>>> Given a "src" and "dst"(empty) dir these two ways of calling mv behaves differently:
>>>> 
>>>> mv src dst/ (work: no copy)
>>>> mv src dst/src (copy, then delete)
>>>> 
>>>> I've attached an strace output for both Lustre and XFS. It seems like mv is handling the fact that Lustre don't have renameat2 a bit differently.
>>>> 
>>>> Before I dig further. Is this behavior known?
>>>> 
>>>> Cheers,
>>>> Hans Henrik
>>>> 
>>>> [1] http://lists.lustre.org/pipermail/lustre-discuss-lustre.org/2023-February/018511.html
>>>> <lustre-mv.strace><xfs-mv.strace><lustre-mv-copy.strace>_______________________________________________
>>>> lustre-discuss mailing list
>>>> lustre-discuss at lists.lustre.org
>>>> http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org
>>>> 
>>>> 
> Cheers,
> Hans Henrik
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Andreas Dilger
Principal Lustre Architect
adilger at thelustrecollective.com