Re: [patch 1/2] raid6_end_write_request() spinlock fix

[Neil Brown <neilb@suse.de>]

On Tuesday April 25, qiyong@fc-cn.com wrote:
> On Tue, Apr 25, 2006 at 03:13:49PM +1000, Neil Brown wrote:
> > On Tuesday April 25, qiyong@fc-cn.com wrote:
> > > Hello,
> > > 
> > > Reduce the raid6_end_write_request() spinlock window.
> > 
> > Andrew: please don't include these in -mm.  This one and the
> > corresponding raid5 are wrong, and I'm not sure yet the unplug_device
> > changes.
> 
> I am sure with the unplug_device. Just look follow the path...
> 

What path?  There are probably several.  If I follow the path, will I
see the same things as you see?  Who knows, because you haven't
bothered to tell us what you see.

> 
> Yes. Let's fix the error(). In any case, the current code is broken. (see raid5/6_end_read_request)

What will I see in raidX_end_read_request.  Surely it isn't that hard
to write a few more sentences?


> Comments? Thanks.

conf->working_disks isn't atomic_t and so decrementing without a
spinlock isn't safe.  So lets just leave it all inside a spinlock.

Also I have a vague memory that clearing In_sync before Faulty is
important, but I'm not certain of that.

Remember: the code is there for a reason.  It might not be a good
reason, and the code could well be wrong.  But it would be worth your
effort trying to find out what the reason is before blithely changing
it (as I discovered recently with a change I suggested to
invalidate_mapping_pages).

NeilBrown
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