linux-kernel - mempool_alloc_bulk and various mempool improvements v3

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Message-ID: <20251113084022.1255121-1-hch@lst.de>
Date: Thu, 13 Nov 2025 09:39:41 +0100
From: Christoph Hellwig <hch@....de>
To: Vlastimil Babka <vbabka@...e.cz>,
	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>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	Brendan Jackman <jackmanb@...gle.com>,
	Zi Yan <ziy@...dia.com>,
	Eric Biggers <ebiggers@...nel.org>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: mempool_alloc_bulk and various mempool improvements v3

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.

Changes since v2:
 - improve the alloc_pages_bulk documentation a bit
 - drop the not needed race fix again
 - drop the gfp_mask argument to mempool_alloc_bulk to reduce misuse
   potential
 - add an allocated argument to mempool_alloc_bulk
 - drop the caller_ip handling that was already not required since the
   last version
 - add a few more mempool cleanups

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      |   58 ++----
 mm/mempool.c                 |  401 ++++++++++++++++++++++++++-----------------
 mm/page_alloc.c              |   15 +
 4 files changed, 289 insertions(+), 193 deletions(-)