GNU bug report logs - #43062
--expose in vm does not reflect file modifications in guest

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Message #8 received at 43062 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: 43062 <at> debbugs.gnu.org,  elaexuotee <at> wilsonb.com
Cc: Christopher Baines <mail <at> cbaines.net>
Subject: Re: bug#43062: --expose in vm does not reflect file modifications in
 guest
Date: Fri, 28 Aug 2020 16:11:26 +0200

[Message part 1 (text/plain, inline)]

Hi,

elaexuotee--- via Bug reports for GNU Guix <bug-guix <at> gnu.org> skribis:

> When using --expose to mirror a path between host and guest, the guest mirror
> fails to reflect file modifications from the host. However, file creation and
> deletion are correctly propogated.
>
> To pick up file modifications in the guest, it is sufficient to remount
> mirroring 9p filesystem.
>
> Is this behaviour expected?

I believe this comes from the “cache=loose” 9p mount option added in
commit e0d96774dd48c29ccc4c90fea1f8f71850ab0879.

Does the patch below help?

Chris, what do you think?  How would this affect the performance issues
that led to e0d96774dd48c29ccc4c90fea1f8f71850ab0879?

Thanks,
Ludo’.

[Message part 2 (text/x-patch, inline)]

diff --git a/gnu/system/vm.scm b/gnu/system/vm.scm
index 861f2a427a..80a8618729 100644
--- a/gnu/system/vm.scm
+++ b/gnu/system/vm.scm
@@ -699,7 +699,8 @@ of the GNU system as described by OS."
        (device (file-system->mount-tag source))
        (type "9p")
        (flags (if writable? '() '(read-only)))
-       (options "trans=virtio,cache=loose")
+       (options (string-append "trans=virtio"
+                               (if writable? "" ",cache=loose")))
        (check? #f)
        (create-mount-point? #t)))))
 

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