Description of problem:
Services malfunction after some days of inactivity (for example mysql)

Version-Release number of selected component (if applicable):
systemd-44-23.fc17
tmpwatch-2.10.3-2.fc17

How reproducible:
always

Steps to Reproduce:
1. start mysqld (systemctl start mysqld.service)
2. wait 10 days - /tmp/systemd-namespace-xxxxx is deleted
3. try to run a mysql query which writes to /tmp:
"Can't create/write to file '/tmp/#sql_696_0.MYI' (Errcode: 2)"

strace -e trace=file:
[pid 15889] lstat("/tmp", {st_mode=S_IFDIR|S_ISVTX|0777, st_size=0, ...}) = 0
[pid 15889] lstat("/tmp/#sql_696_0.MYI", 0x7fb3579e07b0) = -1 ENOENT (No such file or directory)
[pid 15889] open("/tmp/#sql_696_0.MYI", O_RDWR|O_CREAT|O_EXCL|O_TRUNC|O_NOFOLLOW, 0660) = -1 ENOENT (No such file or directory)
[pid 15889] lstat("/tmp/#sql_696_0.MYI", 0x7fb3579e2e60) = -1 ENOENT (No such file or directory)
[pid 15889] unlink("/tmp/#sql_696_0.MYI") = -1 ENOENT (No such file or directory)

excerpt from /proc/<mysqld-pid>mountinfo:
121 86 253:1 /tmp/systemd-namespace-Ej9Z5G/private//deleted /tmp rw,relatime - ext4 /dev/mapper/ssdvg-rootlv rw,seclabel,data=ordered
122 86 253:1 /tmp/systemd-namespace-Ej9Z5G/private//deleted /var/tmp rw,relatime - ext4 /dev/mapper/ssdvg-rootlv rw,seclabel,data=ordered

So systemd and tmpwatch seem to not play well together.

A solution could be that systemd itself would touch all currently used namespace directories every day. That way tmpwatch could still remove old namespace directories.