Re-starting a gjournal provider

[Anthony Chavez]

Hello freebsd-fs,

I'm trying to get gjournal working on a "removable" hard disk.  I use
the term loosely, because I'm using a very simple eSATA enclosure: an
AMS Venus DS5 [1].

If I swap out disks, atacontrol cap ad0 seems sufficient enough to
detect the new drive: the reported device model, serial number, firmware
revision, and CHS values change as one would expect.

My interpretation of [2] section 5.3 and gjournal(8) is that the
following sequence of commands should ensure me that all write buffers
have been flushed and bring the system to a point where it is safe to
remove a disk.

sync; sync; sync
gjournal sync
umount /dev/ad0s1.journal
gjournal stop ad0s1.journal

However, once they are executed, /dev/ad0s1.journal disappears and when
I swap out the disk it doesn't come back.  The only way I've found to
bring it back is atacontrol detach ata0; atacontrol attach ata0, which
doesn't seem like a wise thing to do if I have another device on the
same channel.

My question is, do I need to issue gjournal stop before I swap disks?
And if so, is there any way that I can avoid the atacontrol
detach/attach cycle that would need to take place before any mount is
attempted so that /dev/ad0s1.journal appears (if in the drive inserted
at the time does in fact utilize gjournal; I may want to experiment with
having disks with either gjournal or soft updates)?

And while I'm on the subject, are the (gjournal) syncs commands
preceeding umount absolutely necessary in the case of removable media?

[1] http://www.american-media.com/product/external/ds/ds.html

[2] http://www.freebsd.org/doc/en/articles/gjournal-desktop/article.html

-- 
Anthony Chavez                                  http://hexadecagram.org/
mailto:acc at hexadecagram.org                    xmpp:acc at hexadecagram.org

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