linux-kernel - Re: [PATCH 2/3] xfs: add kmem_alloc

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Message-ID: <20190822075948.GA31346@infradead.org>
Date:   Thu, 22 Aug 2019 00:59:48 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Dave Chinner <david@...morbit.com>
Cc:     linux-xfs@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2/3] xfs: add kmem_alloc_io()

On Thu, Aug 22, 2019 at 10:31:32AM +1000, Dave Chinner wrote:
> > Btw, I think we should eventually kill off KM_NOFS and just use
> > PF_MEMALLOC_NOFS in XFS, as the interface makes so much more sense.
> > But that's something for the future.
> 
> Yeah, and it's not quite as simple as just using PF_MEMALLOC_NOFS
> at high levels - we'll still need to annotate callers that use KM_NOFS
> to avoid lockdep false positives. i.e. any code that can be called from
> GFP_KERNEL and reclaim context will throw false positives from
> lockdep if we don't annotate tehm correctly....

Oh well.  For now we have the XFS kmem_wrappers to turn that into
GFP_NOFS so we shouldn't be too worried, but I think that is something
we should fix in lockdep to ensure it is generally useful.  I've added
the maintainers and relevant lists to kick off a discussion.