On 8/18/23 15:11, songmuhan@xxxxxxxxxxxxxx wrote:
I apologize for any inconvenience, but I have encountered a challenging situation while analyzing the Ceph filesystem's behavior during concurrent rename operations across directories. Specifically, my concern revolves around the potential for directory loops when two clients initiate renames simultaneously.
In the VFS, there's a filesystem-specific vfs_rename_mutex that serializes the rename operation. In Ceph, I noticed the presence of a global client lock. However, I'm uncertain if the MDS serializes rename requests.
Consider the following scenario:
a
/ \
b c
/ \
d e
/ \
f g
If Client 1 attempts to rename "c" to "f" while Client 2 tries to rename "b" to "g" concurrently, and both succeed, we could end up with a loop in the directory structure.
Do you mean 'move' here ? If yes, then the second rename request should
fail, please see:
https://github.com/ceph/ceph/blob/main/src/mds/Server.cc#L8810-L8816
BTW, have hit any issue about this or have you reproduced it ? If so
then it should be a bug.
Thanks
- Xiubo
Could you please provide clarity on how CephFS handles such situations? Your insights would be invaluable.
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