[lustre-discuss] DNE v3 and directory inode changing

[Bertschinger, Thomas Andrew Hjorth]

Hello,

We've been experimenting with DNEv3 recently and have run into this issue: https://jira.whamcloud.com/browse/LU-7607 where the directory inode number changes after auto-split.

In addition to the problem noted with backups that track the inode number, we have found that file access through a previously open file descriptor is broken post migration. This can occur when a shell's CWD is the affected directory. For example:

mds0 # lctl get_param mdt.mylustre-MDT0000.{dir_split_count,enable_dir_auto_split}
mdt.mylustre-MDT0000.dir_split_count=100
mdt.mylustre-MDT0000.enable_dir_auto_split=1

client $ pwd
/mnt/mylustre/dnetest
client $ for i in {0..100}; do touch file$i; done
client $ ls
ls: cannot open directory '.': Operation not permitted
client $ ls file0
ls: cannot access 'file0': No such file or directory
client $ ls /mnt/mylustre/dnetest/file0
/mnt/mylustre/dnetest/file0

(This is from a build of the current master branch.)

We believe users will certainly encounter this, because users monitor output directories of jobs as they run. Therefore this issue is a dealbreaker with DNEv3 for us.

I wanted to ask about the status of the linked issue, since it looks like it hasn't been updated in a while. Would the resolution to LU-7607 be expected to fix the file access problem I've noted here or will this require additional changes to resolve? 

Thanks!

- Thomas Bertschinger