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Date: Fri, 15 Dec 2017 10:42:56 -0800
From: Matthew Wilcox <willy@infradead.org>
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Subject: Re: [Qemu-devel] [PATCH v19 3/7] xbitmap: add more operations
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To: Wei Wang <wei.w.wang@intel.com>
Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, mst@redhat.com, mhocko@kernel.org, akpm@linux-foundation.org, mawilcox@microsoft.com, david@redhat.com, penguin-kernel@I-love.SAKURA.ne.jp, cornelia.huck@de.ibm.com, mgorman@techsingularity.net, aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, liliang.opensource@gmail.com, yang.zhang.wz@gmail.com, quan.xu@aliyun.com, nilal@redhat.com, riel@redhat.com

On Tue, Dec 12, 2017 at 07:55:55PM +0800, Wei Wang wrote:
> +int xb_preload_and_set_bit(struct xb *xb, unsigned long bit, gfp_t gfp);

I'm struggling to understand when one would use this.  The xb_ API
requires you to handle your own locking.  But specifying GFP flags
here implies you can sleep.  So ... um ... there's no locking?

> +void xb_clear_bit_range(struct xb *xb, unsigned long start, unsigned long end);

That's xb_zero() which you deleted with the previous patch ... remember,
keep things as close as possible to the bitmap API.