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	Wed, 27 May 2026 13:23:43 +0000
Date: Wed, 27 May 2026 14:23:43 +0100
From: Matthew Wilcox <willy@infradead.org>
To: Christoph Hellwig <hch@lst.de>
Cc: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Michal Hocko <mhocko@suse.com>,
	Brendan Jackman <jackmanb@google.com>,
	Johannes Weiner <hannes@cmpxchg.org>, Zi Yan <ziy@nvidia.com>,
	Chuck Lever <chuck.lever@oracle.com>, linux-nfs@vger.kernel.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: revisiting alloc_pages_bulks semantics?
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References: <20260527071816.GA17632@lst.de>
 <df21e8b0-a67b-4b71-8178-91221b596949@kernel.org>
 <20260527121920.GB6079@lst.de>
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On Wed, May 27, 2026 at 02:19:20PM +0200, Christoph Hellwig wrote:
> > > There is one single user (svc_fill_pages in sunrpc) that relies on it.
> > > For everyone else it creates extra burden and is very error prone
> > > (speaking from experience).
> > 
> > Sounds good to me. Will sunrpc be easy to convert, or should it be another
> > flag to opt-in to the current behavior, that it would use?
> 
> I've added Chuck to the Cc list, but from memory sunrpc actually does
> make use of this feature and he objected to previous attempts to
> change it.  So a first step would be to have a lower-level helper
> that works as-is and a wrapper that zeroes the array, even if that
> doesn't feel as efficient as it could be.

I think the problem is that sunrpc uses the pages as a queue instead of
a stack.  If it consumed pages from the end instead of the beginning,
it could just refill the entire tail of the array.