linux-kernel - Re: mempool_alloc_bulk and various mempool improvements

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Message-ID: <48e45106-f76a-421d-8f9c-645469076ad4@suse.cz>
Date: Wed, 12 Nov 2025 13:22:01 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Christoph Hellwig <hch@....de>, Andrew Morton <akpm@...ux-foundation.org>
Cc: Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>,
 Roman Gushchin <roman.gushchin@...ux.dev>, Harry Yoo <harry.yoo@...cle.com>,
 Eric Biggers <ebiggers@...nel.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: mempool_alloc_bulk and various mempool improvements

On 11/11/25 14:52, Christoph Hellwig wrote:
> Hi all,
> 
> this series adds a bulk version of mempool_alloc that makes allocating
> multiple objects deadlock safe.
> 
> The initial users is the blk-crypto-fallback code:
> 
>   https://lore.kernel.org/linux-block/20251031093517.1603379-1-hch@lst.de/
> 
> with which v1 was posted, but I also have a few other users in mind.

How do we handle this then once it's settled?

> Changes since v1:
>  - fix build for !CONFIG_FAULT_INJECTION
>  - improve the kerneldoc comments further
>  - refactor the code so that the mempool_alloc fastpath does not
>    have to deal with arrays
>  - don't support !__GFP_DIRECT_RECLAIM for bulk allocations
>  - do poll allocations even if not all elements are available
>  - s/elem/elems/
>  - use a separate failure injection know for the bulk allocator
> 
> diffstat:
>  include/linux/fault-inject.h |    8 -
>  include/linux/mempool.h      |    7 
>  mm/mempool.c                 |  341 ++++++++++++++++++++++++++++---------------
>  3 files changed, 240 insertions(+), 116 deletions(-)