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

Vlastimil Babka
2025-11-05T14:04:59Z

On 10/31/25 10:34, Christoph Hellwig wrote:
> 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>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> 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)) {