[systemd-devel] consider dropping defrag of journals on btrfs

[Phillip Susi]

Phillip Susi writes:

> Wait, what do you mean the inode nr changes?  I thought the whole point
> of the block donating thing was that you get a contiguous set of blocks
> in the new file, then transfer those blocks back to the old inode so
> that the inode number and timestamps of the file don't change.

I just tested this with e4defrag and the inode nr does not change.
Oddly, it refused to improve my archived journals which had 12-15
fragments.  I finally found /var/log/btmp.1 which despite being less
than 8mb had several hundred fragments.  e4defrag got it down to 1
fragment, but for some reason, it is still described by 3 separate
entries in the extent tree.

Looking at the archived journals though, I wonder why am I seeing so
many unwritten areas?  Just the last extent of this file has nearly 4 mb
that were never written to.  This system has never had an unexpected
shutdown.  Attached is the extent map.

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