intermittent rsync errors

[Joseph Maher]

FYI: I'm using rsync with target s3ql 3.7.3 running on the google storage
backend. When I'm rsyncing a reasonably large directory tree, I'll get a
couple of files that won't transfer:

rsync -av --delete-after --inplace --exclude=ariadne/home/untrusted/.cache/spotify/Data/* --exclude=ariadne/home/**/cache2/* --exclude=ariadne/home/maher/.cache/chromium/Default/Cache/* /mnt/backup/snapshots/monthly/current-20210301/ /mnt/s3ql/snapshots/monthly/current-20210301/
building file list ... done
ariadne/var/spool/cups/tmp/cups-dbus-notifier-lockfile
beanhead3/var/spool/cups/tmp/cups-dbus-notifier-lockfile
chekhov/tmp/.X1024-lock
chekhov/tmp/.X1025-lock
rsync: [receiver] open
"/mnt/s3ql/snapshots/monthly/current-20210301/ariadne/var/spool/cups/tmp/cups-dbus-notifier-lockfile"
failed: Permission denied (13)
linode/var/lib/php/sessions/sess_vpl18qhja9q86aainhvr5ppnaa
rsync: [receiver] open
"/mnt/s3ql/snapshots/monthly/current-20210301/beanhead3/var/spool/cups/tmp/cups-dbus-notifier-lockfile"
failed: Permission denied (13)
rsync: [receiver] open
"/mnt/s3ql/snapshots/monthly/current-20210301/chekhov/tmp/.X1024-lock"
failed: Permission denied (13)
rsync: [receiver] open
"/mnt/s3ql/snapshots/monthly/current-20210301/chekhov/tmp/.X1025-lock"
failed: Permission denied (13)
rsync: [receiver] open
"/mnt/s3ql/snapshots/monthly/current-20210301/linode/var/lib/php/sessions/sess_vpl18qhja9q86aainhvr5ppnaa"
failed: Permission denied (13)

sent 161,650,264 bytes received 138 bytes 100,000.25 bytes/sec
total size is 1,106,293,117,551 speedup is 6,843.74
rsync error: some files/attrs were not transferred (see previous errors)
(code 23) at main.c(1330) [sender=3.2.3]


However, if I then rsync each individual directory:

rsync -av --delete /mnt/backup/snapshots/monthly/current-20210301/ariadne/var/spool/cups/tmp/ /mnt/s3ql/snapshots/monthly/current-20210301/ariadne/var/spool/cups/tmp/

[didn't keep the output for this one but it worked]

then rsync works fine to copy / update the new files. I'm not seeing
anything in mount.log...

Joseph