Re: Trying to port data-logging to RH 2.4.18-19.7.x kernel

[Chris Mason <mason@suse.com>]

On Fri, 2003-01-31 at 10:43, John Dalbec wrote:
> Chris Mason wrote:
> > On Fri, 2003-01-31 at 09:41, John Dalbec wrote:
> > 
> >>I'm trying to port Chris's data-logging patches to the Red Hat 
> >>2.4.18-19.7.x kernel.  My first effort works fine on my workstation with 
> >>ReiserFS and NFS, but not on the production server:
> >>
> >>
> >>>Jan 31 05:47:28 mail03 kernel: search_by_key called without kernel lock held
> >>
> > 
> > This is a debugging check that shows our search_by_key function was
> > called without first taking the big kernel lock, and the trace below
> > shows it happened during a call to reiserfs_read_inode2.  So, what you
> > need to do is put lock_kernel() calls into reiserfs_read_inode2, or more
> > likely into reiserfs_lookup.
> 
> I don't see reiserfs_lookup in the stack trace, and it already calls 
> reiserfs_check_lock_depth.  Why would I need lock_kernel there?
> Red Hat's low-latency patch puts a conditional_schedule at the top of 
> search_by_key.  Would that cause the kernel lock to be dropped?  I see
> /* The function is NOT SCHEDULE-SAFE! */
> 

Must be the iget4 path then, probably triggered by nfs.  The locking
rules say the BKL is supposed to be held when you call read_inode.  The
fix would either to be finding the caller or just adding lock_kernel
calls to reiserfs_read_inode2.  It is safe to nest them, so adding them
won't cause problems.

The BKL is dropped during a schedule, but taken again before returning
control to the calling function, so that low latency patch probably
isn't causing problems.  I'm assuming they are using Andrew Morton's low
latency patch, which doesn't cause problems.

-chris