The patch titled Subject: mm: fix unexpected changes to {failslab|fail_page_alloc}.attr has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-fix-unexpected-changes-to-failslabfail_page_allocattr.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Qi Zheng zhengqi.arch@bytedance.com Subject: mm: fix unexpected changes to {failslab|fail_page_alloc}.attr Date: Fri, 18 Nov 2022 18:00:11 +0800

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.

Link: https://lkml.kernel.org/r/20221118100011.2634-1-zhengqi.arch@bytedance.com Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN") Signed-off-by: Qi Zheng zhengqi.arch@bytedance.com Reported-by: Dmitry Vyukov dvyukov@google.com Reviewed-by: Akinobu Mita akinobu.mita@gmail.com Reviewed-by: Jason Gunthorpe jgg@nvidia.com Cc: Akinobu Mita akinobu.mita@gmail.com Cc: Matthew Wilcox willy@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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(-)

--- a/include/linux/fault-inject.h~mm-fix-unexpected-changes-to-failslabfail_page_allocattr +++ a/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, \ }

#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 --- a/lib/fault-inject.c~mm-fix-unexpected-changes-to-failslabfail_page_allocattr +++ a/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(struc * 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) { if (in_task()) { unsigned int fail_nth = READ_ONCE(current->fail_nth); @@ -146,13 +143,20 @@ bool should_fail(struct fault_attr *attr 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 --- a/mm/failslab.c~mm-fix-unexpected-changes-to-failslabfail_page_allocattr +++ a/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 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) --- a/mm/page_alloc.c~mm-fix-unexpected-changes-to-failslabfail_page_allocattr +++ a/mm/page_alloc.c @@ -3887,6 +3887,8 @@ __setup("fail_page_alloc=", setup_fail_p

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) @@ -3897,10 +3899,11 @@ static bool __should_fail_alloc_page(gfp (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 _

Patches currently in -mm which might be from zhengqi.arch@bytedance.com are

mm-fix-unexpected-changes-to-failslabfail_page_allocattr.patch