prealloc failed: operation not supported about gocryptfs

[rfjakob]

Apparently ZFS does not support fallocate ( openzfs/zfs#326 ). gocryptfs uses fallocate to allocate space before it uses it, to prevent running out of space in the middle of an operation, leaving a broken file behind.
I'm not sure how to handle this best.

[v03]

Would it be possible to just check if we have enough space (+some to be safe)? At least under ZFS and simillar, to support it at all.

[rfjakob]

Ok I am checking now if fallocate is not supported at all. In this case, gocrypts will print a warning (only once) and continue working.

Now if the disk runs out of space while writing to a file, the incompletely written block (max 4kB) will be unreadable (it will report an I/O error if you try to read it). But you can still truncate or delete the file.

[rfjakob]

Ok I guess this is resolved. Closing the ticket.