linux-kernel - [PATCH 08/11] mempool: legitimize the io_schedule_timeout in mempool_alloc_from

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Message-ID: <20251113084022.1255121-9-hch@lst.de>
Date: Thu, 13 Nov 2025 09:39:49 +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: [PATCH 08/11] mempool: legitimize the io_schedule_timeout in mempool_alloc_from_pool

The timeout here is and old workaround with a Fixme comment.  But
thinking about it, it makes sense to keep it, so reword the comment.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 mm/mempool.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/mempool.c b/mm/mempool.c
index 88b9a8476d31..ea2f4f9bcfa1 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -427,10 +427,10 @@ static unsigned int mempool_alloc_from_pool(struct mempool *pool, void **elems,
 		spin_unlock_irqrestore(&pool->lock, flags);
 
 		/*
-		 * Wait for someone else to return an element to @pool.
-		 *
-		 * FIXME: this should be io_schedule().  The timeout is there as
-		 * a workaround for some DM problems in 2.6.18.
+		 * Wait for someone else to return an element to @pool, but wake
+		 * up occasionally as memory pressure might have reduced even
+		 * and the normal allocation in alloc_fn could succeed even if
+		 * no element was returned.
 		 */
 		io_schedule_timeout(5 * HZ);
 		finish_wait(&pool->wait, &wait);
-- 
2.47.3