This is a note to let you know that I've just added the patch titled
mm: fix unexpected changes to {failslab|fail_page_alloc}.attr
to the 6.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-fix-unexpected-changes-to-failslab-fail_page_alloc-.attr.patch
and it can be found in the queue-6.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ea4452de2ae987342fadbdd2c044034e6480daad Mon Sep 17 00:00:00 2001
From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Date: Fri, 18 Nov 2022 18:00:11 +0800
Subject: mm: fix unexpected changes to {failslab|fail_page_alloc}.attr
From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
commit ea4452de2ae987342fadbdd2c044034e6480daad upstream.
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.
[akpm@xxxxxxxxxxxxxxxxxxxx: unexport should_fail_ex()]
Link: https://lkml.kernel.org/r/20221118100011.2634-1-zhengqi.arch@xxxxxxxxxxxxx
Fixes: 3f913fc5f974 ("mm: fix missing handler for __GFP_NOWARN")
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Reviewed-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/fault-inject.h | 7 +++++--
lib/fault-inject.c | 13 ++++++++-----
mm/failslab.c | 12 ++++++++++--
mm/page_alloc.c | 7 +++++--
4 files changed, 28 insertions(+), 11 deletions(-)
--- 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, \
}
#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
+++ 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(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 +143,19 @@ 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;
}
+
+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
+++ 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
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
+++ b/mm/page_alloc.c
@@ -3883,6 +3883,8 @@ __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)
@@ -3893,10 +3895,11 @@ 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 stable-queue which might be from zhengqi.arch@xxxxxxxxxxxxx are
queue-6.0/mm-fix-unexpected-changes-to-failslab-fail_page_alloc-.attr.patch
