netdev - Re: [PATCH v2] mm: alloc_pages_bulk: remove assumption of populating only NULL elements

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Message-id: <174173371062.33508.12685894810362310394@noble.neil.brown.name>
Date: Wed, 12 Mar 2025 09:55:10 +1100
From: "NeilBrown" <neilb@...e.de>
To: "Gao Xiang" <hsiangkao@...ux.alibaba.com>
Cc: "Yunsheng Lin" <linyunsheng@...wei.com>,
 "Yunsheng Lin" <yunshenglin0825@...il.com>,
 "Dave Chinner" <david@...morbit.com>, "Yishai Hadas" <yishaih@...dia.com>,
 "Jason Gunthorpe" <jgg@...pe.ca>,
 "Shameer Kolothum" <shameerali.kolothum.thodi@...wei.com>,
 "Kevin Tian" <kevin.tian@...el.com>,
 "Alex Williamson" <alex.williamson@...hat.com>, "Chris Mason" <clm@...com>,
 "Josef Bacik" <josef@...icpanda.com>, "David Sterba" <dsterba@...e.com>,
 "Gao Xiang" <xiang@...nel.org>, "Chao Yu" <chao@...nel.org>,
 "Yue Hu" <zbestahu@...il.com>, "Jeffle Xu" <jefflexu@...ux.alibaba.com>,
 "Sandeep Dhavale" <dhavale@...gle.com>, "Carlos Maiolino" <cem@...nel.org>,
 "Darrick J. Wong" <djwong@...nel.org>,
 "Andrew Morton" <akpm@...ux-foundation.org>,
 "Jesper Dangaard Brouer" <hawk@...nel.org>,
 "Ilias Apalodimas" <ilias.apalodimas@...aro.org>,
 "David S. Miller" <davem@...emloft.net>, "Eric Dumazet" <edumazet@...gle.com>,
 "Jakub Kicinski" <kuba@...nel.org>, "Paolo Abeni" <pabeni@...hat.com>,
 "Simon Horman" <horms@...nel.org>, "Trond Myklebust" <trondmy@...nel.org>,
 "Anna Schumaker" <anna@...nel.org>, "Chuck Lever" <chuck.lever@...cle.com>,
 "Jeff Layton" <jlayton@...nel.org>, "Olga Kornievskaia" <okorniev@...hat.com>,
 "Dai Ngo" <Dai.Ngo@...cle.com>, "Tom Talpey" <tom@...pey.com>,
 "Luiz Capitulino" <luizcap@...hat.com>,
 "Mel Gorman" <mgorman@...hsingularity.net>, kvm@...r.kernel.org,
 virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org,
 linux-btrfs@...r.kernel.org, linux-erofs@...ts.ozlabs.org,
 linux-xfs@...r.kernel.org, linux-mm@...ck.org, netdev@...r.kernel.org,
 linux-nfs@...r.kernel.org
Subject: Re: [PATCH v2] mm: alloc_pages_bulk: remove assumption of populating
 only NULL elements

On Mon, 10 Mar 2025, Gao Xiang wrote:
> 
>   - Your new api covers narrow cases compared to the existing
>     api, although all in-tree callers may be converted
>     properly, but it increases mental burden of all users.
>     And maybe complicate future potential users again which
>     really have to "check NULL elements in the middle of page
>     bulk allocating" again.

I think that the current API adds a mental burden for most users.  For
most users, their code would be much cleaner if the interface accepted
an uninitialised array with length, and were told how many pages had
been stored in that array.

A (very) few users benefit from the complexity.  So having two
interfaces, one simple and one full-featured, makes sense.

Thanks,
NeilBrown