Re: [PATCH 1/2] mm: fix missing handler for __GFP_NOWARN
From: Qi Zheng
Date: Wed May 11 2022 - 01:29:25 EST
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@xxxxxxxxxxxxx>
---
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