mm: export collect_procs()

ascend inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4OXH9
CVE: NA

-------------------------------------------------

Collect the processes who have the page mapped via collect_procs().

@page if the page is a part of the hugepages/compound-page, we must
using compound_head() to find it's head page to prevent the kernel panic,
and make the page be locked.

@to_kill the function will return a linked list, when we have used
this list, we must kfree the list.

@force_early if we want to find all process, we must make it be true, if
it's false, the function will only return the process who have PF_MCE_PROCESS
or PF_MCE_EARLY mark.

limits: if force_early is true, sysctl_memory_failure_early_kill is useless.
If it's false, no process have PF_MCE_PROCESS and PF_MCE_EARLY flag, and
the sysctl_memory_failure_early_kill is enabled, function will return all tasks
whether the task have the PF_MCE_PROCESS and PF_MCE_EARLY flag.
Signed-off-by: NZhang Jian <zhangjian210@huawei.com>
Reviewed-by: NWeilong Chen <chenweilong@huawei.com>
Reviewed-by: Kefeng Wang<wangkefeng.wang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

include/linux/mm.h

@@ -2866,6 +2866,8 @@ extern int sysctl_memory_failure_recovery;
 extern void shake_page(struct page *p, int access);
 extern atomic_long_t num_poisoned_pages __read_mostly;
 extern int soft_offline_page(struct page *page, int flags);
+extern void collect_procs(struct page *page, struct list_head *tokill,
+				int force_early);
 
 
 /*

mm/memory-failure.c

@@ -512,7 +512,7 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
  * First preallocate one tokill structure outside the spin locks,
  * so that we can kill at least one process reasonably reliable.
  */
-static void collect_procs(struct page *page, struct list_head *tokill,
+void collect_procs(struct page *page, struct list_head *tokill,
 				int force_early)
 {
 	struct to_kill *tk;
@@ -529,6 +529,7 @@ static void collect_procs(struct page *page, struct list_head *tokill,
 		collect_procs_file(page, tokill, &tk, force_early);
 	kfree(tk);
 }
+EXPORT_SYMBOL_GPL(collect_procs);
 
 static const char *action_name[] = {
 	[MF_IGNORED] = "Ignored",