x86,mm: make pagefault killable
When an oom killing occurs, almost all processes are getting stuck at the
following two points.
1) __alloc_pages_nodemask
2) __lock_page_or_retry
1) is not very problematic because TIF_MEMDIE leads to an allocation
failure and getting out from page allocator.
2) is more problematic. In an OOM situation, zones typically don't have
page cache at all and memory starvation might lead to greatly reduced IO
performance. When a fork bomb occurs, TIF_MEMDIE tasks don't die quickly,
meaning that a fork bomb may create new process quickly rather than the
oom-killer killing it. Then, the system may become livelocked.
This patch makes the pagefault interruptible by SIGKILL.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/filemap.c b/mm/filemap.c
index dea8a38..8144f87 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -654,15 +654,32 @@
int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
unsigned int flags)
{
- if (!(flags & FAULT_FLAG_ALLOW_RETRY)) {
- __lock_page(page);
- return 1;
- } else {
- if (!(flags & FAULT_FLAG_RETRY_NOWAIT)) {
- up_read(&mm->mmap_sem);
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ /*
+ * CAUTION! In this case, mmap_sem is not released
+ * even though return 0.
+ */
+ if (flags & FAULT_FLAG_RETRY_NOWAIT)
+ return 0;
+
+ up_read(&mm->mmap_sem);
+ if (flags & FAULT_FLAG_KILLABLE)
+ wait_on_page_locked_killable(page);
+ else
wait_on_page_locked(page);
- }
return 0;
+ } else {
+ if (flags & FAULT_FLAG_KILLABLE) {
+ int ret;
+
+ ret = __lock_page_killable(page);
+ if (ret) {
+ up_read(&mm->mmap_sem);
+ return 0;
+ }
+ } else
+ __lock_page(page);
+ return 1;
}
}