Created attachment 816584 [details]
Patch implementing the proposed solution

Description:

I've determined that mlocate's cronjob (/etc/cron.daily/mlocate.cron) doesn't index any ZFS filesystems. 

The reason for this is that the cronjob builds a list of all "nodev" filesystem types listed in /proc/filesystems, which unfortunately includes ZFS.

I can understand mlocate's rationale for doing that (so as to avoid indexing obviously pseudo filesystems like /proc, /sys, etc), but in ZFS case, it's wrong. Also, I can understand ZFS' rationale for listing itself as "nodev": a ZFS filesystem is not directly connected to a device, it's connected to a ZFS pool (which in turn is connected to a device). 

So, it seems we have an unintentional side-effect of the two rationales above. 

To fix it, I patched the cronjob to source a config file (/etc/sysconfig/mlocate) which defines a single env var called NODEV_FS_TO_SCAN_REGEXP; this should be an awk regexp matching every filesystem which should be indexed by mlocate *even* if it's listed as "nodev" in /proc/filesystems; this way, we have a generic fix which can be used for other filesystem types, in case others in the future fall in the same category as ZFS.

Version-Release number of selected component (if applicable): 0.22.2-4.el6 on RHEL 6.4.


How reproducible: 100%


Steps to Reproduce:
1. Run "/etc/cron.daily/mlocate" with a mounted ZFS filesystem;
2. Wait for it to finish;
3. Try to locate any file in the ZFS filesystem using "locate filename"

Actual results:
Files in ZFS filesystem aren't shown by "locate".

Expected results:
Files in ZFS filesystem should be shown by "locate".

Additional info:
Problem originally reported in the zfs-discuss mailing list (see my post here: https://groups.google.com/a/zfsonlinux.org/forum/#!msg/zfs-discuss/nxlya9MNmYc/2u9jZTr2W4oJ); I've fixed the issue and determined that "upstream" in this case is Redhat EL6, so I'm reporting it here along with my patch.