nix/store on btrfs compression: add workaround #4057
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Make archive preallocation (fallocate) optional because some filesystems like btrfs do not behave as expected with fallocate. See NixOS#3550.
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Thanks, I've merged it. We could add auto-detect later if there is interest. |
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See #3550.
As suggested for now I've added a "preallocate-contents" option, and tested by restarting
nix-daemonwith/path/to/output/derivation/bin/nix-daemon --option preallocate-contents falseThis works as a local fix but I definitely want to make this automatic for btrfs.
It's easy to call
statfs(realStoreDir.c_str(), &statfsbuf)and check ifstatfsbuf.f_type == BTRFS_SUPER_MAGIC; the question is how to make the setting "auto" ?I'm thinking of:
--optionswitch? (I'm not too comfortable about introducing such a new setting type...)localStorenext tomakeStoreWritable(e.g. some newcheckFsQuirksmethod?), and if btrfs force the option somehow..globalConfig.set? not really good with code compartimentization :/Needless to say I don't like what I just suggested very much, so suggestions or comments welcome.
This is at least a starting point and folks who care can set the option in their nix.conf until then (depending on timing on the 3.0 release I'd be greedy and ask if it'd be possible to backport in 2.3 maintenance branch, but let's discuss that after we agree on the auto part I guess!)
Thanks!