bug#58205: reconfiguration stuck unless using '--no-grafts'

[Maxim Cournoyer]

Hi,

While working on Berlin today from a chroot, and with --no-substitutes
used for guix-daemon, I wasn't able to complete the 'guix system
reconfigure' step; it'd hand on a read call (seen using strace):

--8<---------------cut here---------------start------------->8---
statfs("/gnu/store", {f_type=BTRFS_SUPER_MAGIC, f_bsize=4096, 
f_blocks=26843282944, f_bfree=14069128626, f_bavail=14067391234, f_files=0, 
f_ffree=0, f_fsid={val=[0x4f5822b0, 0xf74cbbd4]}, f_namelen=255, f_frsize=4096, 
f_flags=ST_VALID|ST_RELATIME}) = 0
write(14, "\t\0\0\0\0\0\0\0\2\0\0\0\0\0\0\0006\0\0\0\0\0\0\0/gnu/sto"..., 152) 
= 152
read(14, "gmlo\0\0\0\0", 8)             = 8
read(14, "\276\0\0\0\0\0\0\0", 8)       = 8
read(14, "@ build-started /gnu/store/kv1gh"..., 192) = 192
)     = 12
write(2, "applying 3 grafts for guix-1.3.0"..., 48applying 3 grafts for 
guix-1.3.0-29.9e46320 ...
) = 48
read(14, "gmlo\0\0\0\0", 8)             = 8
read(14, "\255\0\0\0\0\0\0\0", 8)       = 8
read(14, "@ build-log 17291 151\ngrafting '"..., 176) = 176
\)                = 5
read(14,
--8<---------------cut here---------------end--------------->8---

After passing --no-grafts to 'guix system reconfigure', it could
complete without any error.

-- 
Thanks,
Maxim