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Date:   Wed, 19 Jan 2022 13:20:56 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     JeffleXu <jefflexu@linux.alibaba.com>
Cc:     dhowells@redhat.com, linux-cachefs@redhat.com, xiang@kernel.org,
        chao@kernel.org, linux-erofs@lists.ozlabs.org,
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        gerry@linux.alibaba.com, eguan@linux.alibaba.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 19/23] cachefiles: implement .demand_read() for demand
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On Wed, Jan 12, 2022 at 05:02:13PM +0800, JeffleXu wrote:
> I'm afraid IDR can't be replaced by xarray here. Because we need an 'ID'
> for each pending read request, so that after fetching data from remote,
> user daemon could notify kernel which read request has finished by this
> 'ID'.
> 
> Currently this 'ID' is get from idr_alloc(), and actually identifies the
> position of corresponding read request inside the IDR tree. I can't find
> similar API of xarray implementing similar function, i.e., returning an
> 'ID'.

xa_alloc().