Am 15.01.25 um 11:50 schrieb Fabian Grünbichler: > >> Fiona Ebner <f.eb...@proxmox.com> hat am 15.01.2025 11:46 CET geschrieben: >> >> >> Am 15.01.25 um 11:15 schrieb Fabian Grünbichler: >>> >>>> Fiona Ebner <f.eb...@proxmox.com> hat am 15.01.2025 11:06 CET geschrieben: >>>> >>>> >>>> Am 15.01.25 um 10:51 schrieb Fabian Grünbichler: >>>>> >>>>> basically what we have is the following situation: >>>>> >>>>> - we have some input data (volid+snapname) >>>>> - we have a key derived from the input data (block node name) >>>>> - we have a value (block node) >>>>> - we need to be be able to map back the block node (name) to the input >>>>> data >>>> >>>> Oh, we need to map back too? But that can be done via filename in the >>>> block node, or not? >>> >>> but that filename is the result of PVE::Storage::path which is not stable, >>> so we can't compare that? >>> >>> for snapshot operations, we need to find out "which block node is the one >>> for the snapshot volume". we can't rely on the filename in the block graph >>> for that, because how we map from volid+snapname to that filename might >>> have changed on our end since that bock node was set up. so we need to find >>> a way to map using (parts of) the block node name, which means >>> - having a naming scheme that allows to map back from node name to >>> volid+snapname (i.e., the hashing scheme we are discussing ;)) >>> - never re-using a block node for something other than what is encoded in >>> its name (not sure if that possible?) >>> >>> while an operation is ongoing, we can have $prefix-$hash-1 and >>> $prefix-$hash-2 at the same time, and if we then end up with having just >>> $prefix-$hash-2 after the operation that doesn't matter since we can >>> reliably map that back via the $hash to volid+snapname. >> >> How would you map back from the hash? Wouldn't that require computing >> the hashes for all known volid+snapname and comparing which one matches? >> Or do you mean having a lookup-table, i.e. Perl hash keeping track of >> the hash => volid+snapname mappings? > > if you are looking for the block node currently referencing volid A in > snapshot X, you calculate the hash for them, and then look at the list of > block nodes which should only contain one block node named using that hash. > "mapping back" is a bit of a misnomer I guess ;) we just want to know which > node corresponds to a *known* input pair, not get the input pair from the > node alone.
Yes, I was confused by "mapping back". Thanks for the clarification! _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
