filefrag and btrfs filesystem defragment and maybe snapshots

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While exploring some btrfs maintenance with respect to defragmenting I
ran the following commands:

# filefrag /path/to/34G.file /path/to/5.7G.file
/path/to/34G.file: 2406 extents found
/path/to/5.7G.file: 572 extents found

Thinking those mostly static files could be less fragmented I ran:
# btrfs filesystem defragment -c /path/to/34G.file
# btrfs filesystem defragment -c /path/to/5.7G.file

and to my surprise the number of fragments/extends doubled:

# filefrag /path/to/34G.file /path/to/5.7G.file
/path/to/34G.file: 6324 extents found
/path/to/5.7G.file: 1079 extents found

Did I actually improve these files?

I do have a number rolling readonly snapshots on the subvolume these
files are on. I can imagine how that might be related but I'm not
sure. When the pre-defrag snapshots are purged will the filefrag
extents count drop.

-- 
Sandy McArthur

"He who dares not offend cannot be honest."
- Thomas Paine
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