System deadlock when using mksnap_ffs

[Greg Byshenk]

On Wed, Nov 12, 2008 at 08:42:00PM -0800, Jeremy Chadwick wrote:
 
> The rest of the below information is good -- but I'm confused about
> something: is there anyone out there who can use mksnap_ffs on a
> filesystem (/usr is a good test source) and NOT experience this
> deadlocking problem?  Literally *every* FreeBSD box I have root access
> to suffers from this problem, so I'm a little baffled why we end-users
> need to keep providing debugging output when it should be easy as pie
> for a developer to do "dump -0 -L -a -f /path/fs.dump /usr" and watch
> their system wedge.

As an answer to the question (and additional information), I am 
experiencing the problem, but not on all filesystems. 

This is under FreeBSD 7.1-PRERELEASE #7: Thu Nov  6 11:29:52 CET 2008,
amd64 (from sources csup'ed immediately prior to the build).

I have four filesystems used for data storage:

/dev/da1p1    96850470   7866026   81236408     9%    /export/mail
/dev/da1p2  1937058312 972070320  810023328    55%    /export/home
/dev/da1p3  1937058312  79027008 1703066640     4%    /export/misc
/dev/da1p4  2598991534 271980564 2119091648    11%    /export/spare

I can successfully mksnap_ffs the first (smaller) partition, but an
attempt to do so on any of the others causes a lock.

Note: this is a lockup, not a "slow".  The system becomes unresponsive
to any input, and there is no hard drive activity, and this does not
change over a period of more than 12 hours.

-- 
greg byshenk  -  gbyshenk at byshenk.net  -  Leiden, NL