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Date:   Fri, 8 Mar 2019 09:18:07 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     Matthew Wilcox <willy@infradead.org>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        Ming Lei <ming.lei@redhat.com>,
        Ming Lei <tom.leiming@gmail.com>,
        Dave Chinner <david@fromorbit.com>,
        "open list:XFS FILESYSTEM" <linux-xfs@vger.kernel.org>,
        Jens Axboe <axboe@kernel.dk>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Dave Chinner <dchinner@redhat.com>,
        Christoph Hellwig <hch@lst.de>,
        Alexander Duyck <alexander.h.duyck@linux.intel.com>,
        Aaron Lu <aaron.lu@intel.com>,
        Christopher Lameter <cl@linux.com>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        linux-block <linux-block@vger.kernel.org>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH] xfs: allocate sector sized IO buffer via
 page_frag_alloc
Message-ID: <20190308081807.GB12909@lst.de>
References: <a641feb8-ceb2-2dac-27aa-7b1df10f5ae5@suse.cz> <CACVXFVMX=WpTRBbDTSibfXkTZxckk3ootetbE+rkJtHhsZkRAw@mail.gmail.com> <20190226121209.GC11592@bombadil.infradead.org> <20190226123545.GA6163@ming.t460p> <20190226130230.GD11592@bombadil.infradead.org> <20190226134247.GA30942@ming.t460p> <20190226140440.GF11592@bombadil.infradead.org> <20190226161433.GH21626@magnolia> <20190226161912.GG11592@bombadil.infradead.org> <095ae112-f98e-9516-910a-43b49ea5bf0d@suse.cz>
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On Wed, Feb 27, 2019 at 08:07:31AM +0100, Vlastimil Babka wrote:
> > I don't know _what_ Ming Lei is saying.  I thought the problem was
> > with slab redzones, which need to be before and after each object,
> > but apparently the problem is with KASAN as well.
> 
> That's what I thought as well. But if we can solve it for caches created
> by kmem_cache_create(..., align, ...) then IMHO we could guarantee
> natural alignment for power-of-two kmalloc caches as well.

Yes, having a version of kmalloc that guarantees power of two alignment
would be extremely helpful and avoid a lot of pointless boilerplate code.