bug#40447:

[Tobias Geerinckx-Rice]

Brendan,

Brendan Tildesley 写道：
> Closing since it seems to unrelated. Sorry for wasting your 
> time. I
> think it may have been my ext4 having too many files. i deleted 
> all my
> system generations and gc'd a lot of stuff, and it seems to be 
> miss
> behaving. perhaps it is a different kind of guix bug that it 
> doesnt
> cope with this issue:

Worse: it's an ext4 bug (well, behaviour).

> [ 7862.196231] EXT4-fs warning (device sdb1): 
> ext4_dx_add_entry:2343:
> Directory (ino: 24903688) index full, reach max htree level :2

This happens when a directory, almost certainly /gnu/store/.links, 
contains more entries than can fit in ext4's ‘dir_index’ hash 
table.  The file system simply punts.

You can disable this optimisation with tune2fs -O ^dir_index …. 
You'll lose some theoretical performance but I haven't heard 
complaints in practice.  You're not the first one to encounter 
this problem.

If that's unacceptable, you can reconfigure your guix-daemon with 
‘--disable-deduplication’ in exchange for more storage space for 
newer generations.

Or switch to btrfs for a newer, shinier set of pathological 
gotchas but not this one :-)

One could work around this in Guix if one were motivated:
- Ignore file system failure instead of making it fatal, falling 
 back to ‘--disable-deduplication’ behaviour, which is probably 
 the right thing to do; or
- store .links in ./n/e/sted directories, which will degrade 
 performance on file systems that handle collisions properly and 
 is probably not worth the headache.

Kind regards,

T G-R

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