[PATCH 2/9] mempool: add error injection support

Christoph Hellwig
2025-10-31T09:35:34Z

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@lst.de>
---
mm/mempool.c | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/mm/mempool.c b/mm/mempool.c
index d7c55a98c2be..15581179c8b9 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)
@@ -399,10 +408,15 @@ void *mempool_alloc_noprof(mempool_t *pool, gfp_t gfp_mask)
gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO);

repeat_alloc:
-
- element = pool->alloc(gfp_temp, pool->pool_data);
- if (likely(element != NULL))
- return element;
+ if (should_fail_ex(&fail_mempool_alloc, 1, FAULT_NOWARN)) {
+ pr_info("forcing mempool usage for pool %pS\n",
+ (void *)_RET_IP_);
+ element = NULL;
+ } else {
+ element = pool->alloc(gfp_temp, pool->pool_data);
+ if (likely(element != NULL))
+ return element;
+ }

spin_lock_irqsave(&pool->lock, flags);
if (likely(pool->curr_nr)) {
--
2.47.3