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Date: Wed, 11 May 2022 13:28:53 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
akinobu.mita@...il.com, vbabka@...e.cz, gregkh@...uxfoundation.org,
jirislaby@...nel.org, rostedt@...dmis.org
Subject: Re: [PATCH 1/2] mm: fix missing handler for __GFP_NOWARN
On 2022/5/11 1:12 PM, Qi Zheng wrote:
>
>
> On 2022/5/10 7:38 PM, Qi Zheng wrote:
>> We expect no warnings to be issued when we specify __GFP_NOWARN, but
>> currently in paths like alloc_pages() and kmalloc(), there are still
>> some warnings printed, fix it.
>
> Hi Andrew,
>
> Maybe we only need to deal with memory allocation failures, such as
> should_fail() (This leads to deadlock in PATCH[2/2]). These
> WARN_ON_ONCE()s report usage problems and should not be printed. If they
such as WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1),
gfp_flags).
> are printed, we should fix these usage problems.
>
> Thanks,
> Qi
>
>
>>
>> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
>> ---
>> include/linux/fault-inject.h | 2 ++
>> lib/fault-inject.c | 3 +++
>> mm/failslab.c | 3 +++
>> mm/internal.h | 11 +++++++++++
>> mm/page_alloc.c | 22 ++++++++++++----------
>> 5 files changed, 31 insertions(+), 10 deletions(-)
>>
>> diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h
>> index 2d04f6448cde..9f6e25467844 100644
>> --- a/include/linux/fault-inject.h
>> +++ b/include/linux/fault-inject.h
>> @@ -20,6 +20,7 @@ struct fault_attr {
>> atomic_t space;
>> unsigned long verbose;
>> bool task_filter;
>> + bool no_warn;
>> unsigned long stacktrace_depth;
>> unsigned long require_start;
>> unsigned long require_end;
>> @@ -39,6 +40,7 @@ struct fault_attr {
>> .ratelimit_state = RATELIMIT_STATE_INIT_DISABLED, \
>> .verbose = 2, \
>> .dname = NULL, \
>> + .no_warn = false, \
>> }
>> #define DECLARE_FAULT_ATTR(name) struct fault_attr name =
>> FAULT_ATTR_INITIALIZER
>> diff --git a/lib/fault-inject.c b/lib/fault-inject.c
>> index ce12621b4275..423784d9c058 100644
>> --- a/lib/fault-inject.c
>> +++ b/lib/fault-inject.c
>> @@ -41,6 +41,9 @@ EXPORT_SYMBOL_GPL(setup_fault_attr);
>> static void fail_dump(struct fault_attr *attr)
>> {
>> + if (attr->no_warn)
>> + return;
>> +
>> if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
>> printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
>> "name %pd, interval %lu, probability %lu, "
>> diff --git a/mm/failslab.c b/mm/failslab.c
>> index f92fed91ac23..58df9789f1d2 100644
>> --- a/mm/failslab.c
>> +++ b/mm/failslab.c
>> @@ -30,6 +30,9 @@ bool __should_failslab(struct kmem_cache *s, gfp_t
>> gfpflags)
>> if (failslab.cache_filter && !(s->flags & SLAB_FAILSLAB))
>> return false;
>> + if (gfpflags & __GFP_NOWARN)
>> + failslab.attr.no_warn = true;
>> +
>> return should_fail(&failslab.attr, s->object_size);
>> }
>> diff --git a/mm/internal.h b/mm/internal.h
>> index cf16280ce132..7a268fac6559 100644
>> --- a/mm/internal.h
>> +++ b/mm/internal.h
>> @@ -35,6 +35,17 @@ struct folio_batch;
>> /* Do not use these with a slab allocator */
>> #define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK)
>> +#define WARN_ON_ONCE_GFP(cond, gfp) ({ \
>> + static bool __section(".data.once") __warned; \
>> + int __ret_warn_once = !!(cond); \
>> + \
>> + if (unlikely(!(gfp & __GFP_NOWARN) && __ret_warn_once &&
>> !__warned)) { \
>> + __warned = true; \
>> + WARN_ON(1); \
>> + } \
>> + unlikely(__ret_warn_once); \
>> +})
>> +
>> void page_writeback_init(void);
>> static inline void *folio_raw_mapping(struct folio *folio)
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 0e42038382c1..2bf4ce4d0e2f 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -3722,7 +3722,7 @@ struct page *rmqueue(struct zone *preferred_zone,
>> * We most definitely don't want callers attempting to
>> * allocate greater than order-1 page units with __GFP_NOFAIL.
>> */
>> - WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
>> + WARN_ON_ONCE_GFP((gfp_flags & __GFP_NOFAIL) && (order > 1),
>> gfp_flags);
>> do {
>> page = NULL;
>> @@ -3799,6 +3799,9 @@ static bool __should_fail_alloc_page(gfp_t
>> gfp_mask, unsigned int order)
>> (gfp_mask & __GFP_DIRECT_RECLAIM))
>> return false;
>> + if (gfp_mask & __GFP_NOWARN)
>> + fail_page_alloc.attr.no_warn = true;
>> +
>> return should_fail(&fail_page_alloc.attr, 1 << order);
>> }
>> @@ -4346,7 +4349,8 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned
>> int order,
>> */
>> /* Exhausted what can be done so it's blame time */
>> - if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
>> + if (out_of_memory(&oc) ||
>> + WARN_ON_ONCE_GFP(gfp_mask & __GFP_NOFAIL, gfp_mask)) {
>> *did_some_progress = 1;
>> /*
>> @@ -4902,8 +4906,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned
>> int order,
>> * We also sanity check to catch abuse of atomic reserves being
>> used by
>> * callers that are not in atomic context.
>> */
>> - if (WARN_ON_ONCE((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) ==
>> - (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
>> + if (WARN_ON_ONCE_GFP((gfp_mask &
>> (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) ==
>> + (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM), gfp_mask))
>> gfp_mask &= ~__GFP_ATOMIC;
>> retry_cpuset:
>> @@ -5117,7 +5121,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned
>> int order,
>> * All existing users of the __GFP_NOFAIL are blockable, so
>> warn
>> * of any new users that actually require GFP_NOWAIT
>> */
>> - if (WARN_ON_ONCE(!can_direct_reclaim))
>> + if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask))
>> goto fail;
>> /*
>> @@ -5125,7 +5129,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned
>> int order,
>> * because we cannot reclaim anything and only can loop waiting
>> * for somebody to do a work for us
>> */
>> - WARN_ON_ONCE(current->flags & PF_MEMALLOC);
>> + WARN_ON_ONCE_GFP(current->flags & PF_MEMALLOC, gfp_mask);
>> /*
>> * non failing costly orders are a hard requirement which we
>> @@ -5133,7 +5137,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned
>> int order,
>> * so that we can identify them and convert them to something
>> * else.
>> */
>> - WARN_ON_ONCE(order > PAGE_ALLOC_COSTLY_ORDER);
>> + WARN_ON_ONCE_GFP(order > PAGE_ALLOC_COSTLY_ORDER, gfp_mask);
>> /*
>> * Help non-failing allocations by giving them access to memory
>> @@ -5379,10 +5383,8 @@ struct page *__alloc_pages(gfp_t gfp, unsigned
>> int order, int preferred_nid,
>> * There are several places where we assume that the order value
>> is sane
>> * so bail out early if the request is out of bound.
>> */
>> - if (unlikely(order >= MAX_ORDER)) {
>> - WARN_ON_ONCE(!(gfp & __GFP_NOWARN));
>> + if (WARN_ON_ONCE_GFP(order >= MAX_ORDER, gfp))
>> return NULL;
>> - }
>> gfp &= gfp_allowed_mask;
>> /*
>
--
Thanks,
Qi
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