Pass mp to kmem_alloc and friends?

[Dave Chinner]

On Wed, Jan 20, 2016 at 11:53:54AM -0800, Darrick J. Wong wrote:
> On Wed, Jan 20, 2016 at 11:59:09AM -0600, Eric Sandeen wrote:
> > I had a request for the kmem_alloc deadlock warning to print the
> > filesystem involved.
> > 
> > Any objections to passing mp into kmem_alloc() and friends whenever
> > it's reasonably available from the caller?
> > 
> > It'd be a big mechanical change, don't want to embark on that unless
> > it seems acceptable & useful.
> > 
> > I think we generally know the root causes of the most common deadlock
> > warnings, but it's a warm fuzzy to give as much info as possible.
> > 
> > Heck, I almost wonder if passing a descriptive string in, for at
> > least the problematic cases we know about, i.e. "extent map realloc"
> > so we'd get something like:
> > 
> > XFS (sdb1): myprocess(123) possible memory allocation deadlock size 12345 during extent map realloc in kmem_alloc (mode:0x250)
> > 
> > I dunno ... too much? :)
> 
> Not enough?  What about putting in just enough macro madness to report
> the name & line number of the calling function in the message?
> 
> XFS (sdb1): myprocess(123) possible kmem_alloc deadlock in
> xfs_eat_my_data.c:5135 (size:12345 mode:0x250)

Problem with that is the the return address will often just point to
a higher level wrapper function, and we are still without any
caller context. e.g. if we find the caller is xfs_buf_alloc_maps(),
what operation was being performed that needed a new buffer
allocated?

IMO, the only thing that will actually be useful for debugging at
this point is a full stack dump....

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com