Dear Maintainer, On CephFS, creating a snapshot is done suchly: $ mkdir .snap/snapshot-name
This creates a directory which contains a view of the current directory at the time the snapshot was created, and is therefore non-empty if the current directory was non-empty at that time. Its contents are immutable. Removing a snapshot is done suchly: $ rmdir .snap/snapshot-name This works fine even if .snap/snapshot-name is non-empty, as rmdir calls rmdir(2) directly without trying to be smart, and the Ceph filesystem understands what rmdir on a snapshot directory means: remove the snapshot. One would naturally expect rm -d to behave *exactly the same* as rmdir, but this isn't the case, because rm -d first does a getdents on the directory, observes it is non-empty, and refuses to perform the removal. >From what I understand, this is non-compliant behavior per XCU rm 2.a. and 4. and XSH remove(): https://pubs.opengroup.org/onlinepubs/9799919799/utilities/rm.html > 2. If file is of type directory, the following steps shall be taken: > a. If neither the -R option nor the -r option is specified, but -d > is specified, rm shall proceed with step 3 for the current file. > 4. rm shall perform actions equivalent to the remove() function defined > in the System Interfaces volume of POSIX.1-2024 called with a > pathname of the current file used as the path argument. https://pubs.opengroup.org/onlinepubs/9799919799/functions/remove.html > If path names a directory, remove(path) shall be equivalent to rmdir(path) In short: rm -d .snap/snapshot-name shall be equivalent to: remove(".snap/snapshot-name") which in turn shall be equivalent to: rmdir(".snap/snapshot-name") Moreover other coreutils rm implementations (such as uutils or voreutils) do not exhibit this bug and correctly remove non-empty directories. Regards, Yannick Le Pennec
