Messages in this thread | | | Date | Tue, 8 Nov 2022 16:58:04 +0800 | Subject | Re: [PATCH v2] mm: fix unexpected changes to {failslab|fail_page_alloc}.attr | From | Qi Zheng <> |
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On 2022/11/8 16:44, Wei Yongjun wrote: > Hi Zheng Qi, > > On 2022/11/8 11:52, Qi Zheng wrote: >> When we specify __GFP_NOWARN, we only expect that no warnings >> will be issued for current caller. But in the __should_failslab() >> and __should_fail_alloc_page(), the local GFP flags alter the >> global {failslab|fail_page_alloc}.attr, which is persistent and >> shared by all tasks. This is not what we expected, let's fix it. >> >> Cc: stable@vger.kernel.org >> Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN") >> Reported-by: Dmitry Vyukov <dvyukov@google.com> >> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> >> --- >> v1: https://lore.kernel.org/lkml/20221107033109.59709-1-zhengqi.arch@bytedance.com/ >> >> Changelog in v1 -> v2: >> - add comment for __should_failslab() and __should_fail_alloc_page() >> (suggested by Jason) >> >> include/linux/fault-inject.h | 7 +++++-- >> lib/fault-inject.c | 14 +++++++++----- >> mm/failslab.c | 12 ++++++++++-- >> mm/page_alloc.c | 7 +++++-- >> 4 files changed, 29 insertions(+), 11 deletions(-) >> >> diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h >> index 9f6e25467844..444236dadcf0 100644 >> --- a/include/linux/fault-inject.h >> +++ b/include/linux/fault-inject.h >> @@ -20,7 +20,6 @@ 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; >> @@ -32,6 +31,10 @@ struct fault_attr { >> struct dentry *dname; >> }; >> >> +enum fault_flags { >> + FAULT_NOWARN = 1 << 0, >> +}; >> + >> #define FAULT_ATTR_INITIALIZER { \ >> .interval = 1, \ >> .times = ATOMIC_INIT(1), \ >> @@ -40,11 +43,11 @@ struct fault_attr { >> .ratelimit_state = RATELIMIT_STATE_INIT_DISABLED, \ >> .verbose = 2, \ >> .dname = NULL, \ >> - .no_warn = false, \ > > How about keep no_warn attr as it be, and export it to user? > > When testing with fault injection, and each fault will print an backtrace. > but not all of the testsuit can tell us which one is fault injection > message or other is a real warning/crash like syzkaller do. > > In my case, to make things simple, we usually used a regex to detect whether > wanring/error happend. So we disabled the slab/page fault warning message by > default, and only enable it when debug real issue.
So you want to set/clear this no_warn attr through the procfs or sysfs interface, so that you can easily disable/enable the slab/page fault warning message from the user mode. Right?
Seems reasonable to me. Anyone else has an opinion on this? If it is really needed, I can do it later.
Thanks, Qi
> > Regards, > > >> } >> >> #define DECLARE_FAULT_ATTR(name) struct fault_attr name = FAULT_ATTR_INITIALIZER >> int setup_fault_attr(struct fault_attr *attr, char *str); >> +bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags); >> bool should_fail(struct fault_attr *attr, ssize_t size); >> >> #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS >> diff --git a/lib/fault-inject.c b/lib/fault-inject.c >> index 4b8fafce415c..5971f7c3e49e 100644 >> --- a/lib/fault-inject.c >> +++ b/lib/fault-inject.c >> @@ -41,9 +41,6 @@ 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, " >> @@ -103,7 +100,7 @@ static inline bool fail_stacktrace(struct fault_attr *attr) >> * http://www.nongnu.org/failmalloc/ >> */ >> >> -bool should_fail(struct fault_attr *attr, ssize_t size) >> +bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags) >> { >> bool stack_checked = false; >> >> @@ -152,13 +149,20 @@ bool should_fail(struct fault_attr *attr, ssize_t size) >> return false; >> >> fail: >> - fail_dump(attr); >> + if (!(flags & FAULT_NOWARN)) >> + fail_dump(attr); >> >> if (atomic_read(&attr->times) != -1) >> atomic_dec_not_zero(&attr->times); >> >> return true; >> } >> +EXPORT_SYMBOL_GPL(should_fail_ex); >> + >> +bool should_fail(struct fault_attr *attr, ssize_t size) >> +{ >> + return should_fail_ex(attr, size, 0); >> +} >> EXPORT_SYMBOL_GPL(should_fail); >> >> #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS >> diff --git a/mm/failslab.c b/mm/failslab.c >> index 58df9789f1d2..ffc420c0e767 100644 >> --- a/mm/failslab.c >> +++ b/mm/failslab.c >> @@ -16,6 +16,8 @@ static struct { >> >> bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags) >> { >> + int flags = 0; >> + >> /* No fault-injection for bootstrap cache */ >> if (unlikely(s == kmem_cache)) >> return false; >> @@ -30,10 +32,16 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags) >> if (failslab.cache_filter && !(s->flags & SLAB_FAILSLAB)) >> return false; >> >> + /* >> + * In some cases, it expects to specify __GFP_NOWARN >> + * to avoid printing any information(not just a warning), >> + * thus avoiding deadlocks. See commit 6b9dbedbe349 for >> + * details. >> + */ >> if (gfpflags & __GFP_NOWARN) >> - failslab.attr.no_warn = true; >> + flags |= FAULT_NOWARN; >> >> - return should_fail(&failslab.attr, s->object_size); >> + return should_fail_ex(&failslab.attr, s->object_size, flags); >> } >> >> static int __init setup_failslab(char *str) >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 7192ded44ad0..cb6fe715d983 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -3902,6 +3902,8 @@ __setup("fail_page_alloc=", setup_fail_page_alloc); >> >> static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order) >> { >> + int flags = 0; >> + >> if (order < fail_page_alloc.min_order) >> return false; >> if (gfp_mask & __GFP_NOFAIL) >> @@ -3912,10 +3914,11 @@ static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order) >> (gfp_mask & __GFP_DIRECT_RECLAIM)) >> return false; >> >> + /* See comment in __should_failslab() */ >> if (gfp_mask & __GFP_NOWARN) >> - fail_page_alloc.attr.no_warn = true; >> + flags |= FAULT_NOWARN; >> >> - return should_fail(&fail_page_alloc.attr, 1 << order); >> + return should_fail_ex(&fail_page_alloc.attr, 1 << order, flags); >> } >> >> #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
-- Thanks, Qi
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