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Date: Wed, 11 May 2022 14:24:39 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: akpm@...ux-foundation.org, jirislaby@...nel.org,
akinobu.mita@...il.com, vbabka@...e.cz, gregkh@...uxfoundation.org,
rostedt@...dmis.org
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 1/2] mm: fix missing handler for __GFP_NOWARN
On 2022/5/11 2:19 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.
>
> But for some warnings that report usage problems, we don't deal with
> them. If such warnings are printed, then we should fix the usage
> problems. Such as the following case:
>
> WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
>
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
> ---
Changelog in v1 -> v2:
- add comment to WARN_ON_ONCE_GFP
- handle __alloc_contig_migrate_range() case
- do not deal with:
WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
> include/linux/fault-inject.h | 2 ++
> lib/fault-inject.c | 3 +++
> mm/failslab.c | 3 +++
> mm/internal.h | 15 +++++++++++++++
> mm/page_alloc.c | 18 ++++++++++--------
> 5 files changed, 33 insertions(+), 8 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 e3e50af20706..34fdedb9986f 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -35,6 +35,21 @@ struct folio_batch;
> /* Do not use these with a slab allocator */
> #define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK)
>
> +/*
> + * Different from WARN_ON_ONCE(), no warning will be issued
> + * when we specify __GFP_NOWARN.
> + */
> +#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 65f892af1d4f..f9f329403d76 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3789,6 +3789,9 @@ 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);
> }
>
> @@ -4337,7 +4340,8 @@ __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;
>
> /*
> @@ -5103,7 +5107,7 @@ __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;
>
> /*
> @@ -5111,7 +5115,7 @@ __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
> @@ -5119,7 +5123,7 @@ __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
> @@ -5365,10 +5369,8 @@ 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;
> /*
> @@ -9020,7 +9022,7 @@ int __alloc_contig_migrate_range(struct compact_control *cc,
>
> lru_cache_enable();
> if (ret < 0) {
> - if (ret == -EBUSY)
> + if (!(cc->gfp_mask & __GFP_NOWARN) && ret == -EBUSY)
> alloc_contig_dump_pages(&cc->migratepages);
> putback_movable_pages(&cc->migratepages);
> return ret;
--
Thanks,
Qi
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