linux-kernel - [PATCH 04/11] mempool: add error injection support

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Message-ID: <20251113084022.1255121-5-hch@lst.de>
Date: Thu, 13 Nov 2025 09:39:45 +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 04/11] mempool: add error injection support

Add a call to should_fail_ex that forces mempool to actually allocate
from the pool to stress the mempool implementation when enabled through
debugfs.  By default should_fail{,_ex} prints a very verbose stack trace
that clutters the kernel log, slows down execution and triggers the
kernel bug detection in xfstests.  Pass FAULT_NOWARN and print a
single-line message notating the caller instead so that full tests
can be run with fault injection.

Signed-off-by: Christoph Hellwig <hch@....de>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/mempool.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/mm/mempool.c b/mm/mempool.c
index 1f4701713203..5cf59779cc3d 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -9,7 +9,7 @@
  *  started by Ingo Molnar, Copyright (C) 2001
  *  debugging by David Rientjes, Copyright (C) 2015
  */
-
+#include <linux/fault-inject.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/highmem.h>
@@ -20,6 +20,15 @@
 #include <linux/writeback.h>
 #include "slab.h"
 
+static DECLARE_FAULT_ATTR(fail_mempool_alloc);
+
+static int __init mempool_faul_inject_init(void)
+{
+	return PTR_ERR_OR_ZERO(fault_create_debugfs_attr("fail_mempool_alloc",
+			NULL, &fail_mempool_alloc));
+}
+late_initcall(mempool_faul_inject_init);
+
 #ifdef CONFIG_SLUB_DEBUG_ON
 static void poison_error(mempool_t *pool, void *element, size_t size,
 			 size_t byte)
@@ -404,9 +413,15 @@ void *mempool_alloc_noprof(mempool_t *pool, gfp_t gfp_mask)
 	gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO);
 
 repeat_alloc:
+	if (should_fail_ex(&fail_mempool_alloc, 1, FAULT_NOWARN)) {
+		pr_info("forcing mempool usage for %pS\n",
+				(void *)_RET_IP_);
+		element = NULL;
+	} else {
+		element = pool->alloc(gfp_temp, pool->pool_data);
+	}
 
-	element = pool->alloc(gfp_temp, pool->pool_data);
-	if (likely(element != NULL))
+	if (likely(element))
 		return element;
 
 	spin_lock_irqsave(&pool->lock, flags);
-- 
2.47.3