* [David Arendt]
> I received the message: btrfs: unlinked 34 orphans
>
> Just out of couriosity: what does it mean ?
Ooh, ooh! I think I know this one :)
When a file is unlinked/deleted while an application has it open, it is
kept around allocated on disk so that the app has access to the data in
the file. When the file is closed or the app exits, it is deallocated
(disk space is freed). This is a quite normal way of handling temporary
files.
Now, if there is an unclean shutdown while a file is in this "deleted,
but not freed" state, you get an orphaned file or inode -- that is,
allocated data with no directory entry pointing to it. When btrfs
unlinks these orphans during mount, it''s just completing what would
have
happened once the unlinked files were closed. If this happened after an
unclean shutdown (crash or power loss), the message is just btrfs
bragging about working properly.
None of this is actually specific to btrfs. I believe posix filesystems
are more or less required (or at least expected) to behave like this.
(interestingly, Microsoft Windows has a different take on this issue by
simply not letting you delete open files).
Øystein
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