[RFC 2/4] mm: replace TIF_MEMDIE checks by tsk_is_oom_victim

[Michal Hocko]

From: Michal Hocko <mhocko@xxxxxxxx>

TIF_MEMDIE is set only to the tasks whick were either directly selected
by the OOM killer or passed through mark_oom_victim from the allocator
path. tsk_is_oom_victim is more generic and allows to identify all tasks
(threads) which share the mm with the oom victim.

Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 kernel/cpuset.c | 9 +++++----
 mm/memcontrol.c | 2 +-
 mm/oom_kill.c   | 4 ++--
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index c7fd2778ed50..8e370d9d63ee 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -54,6 +54,7 @@
 #include <linux/time64.h>
 #include <linux/backing-dev.h>
 #include <linux/sort.h>
+#include <linux/oom.h>
 
 #include <asm/uaccess.h>
 #include <linux/atomic.h>
@@ -2487,12 +2488,12 @@ static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
  * If we're in interrupt, yes, we can always allocate.  If @node is set in
  * current's mems_allowed, yes.  If it's not a __GFP_HARDWALL request and this
  * node is set in the nearest hardwalled cpuset ancestor to current's cpuset,
- * yes.  If current has access to memory reserves due to TIF_MEMDIE, yes.
+ * yes.  If current has access to memory reserves as an oom victim, yes.
  * Otherwise, no.
  *
  * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
  * and do not allow allocations outside the current tasks cpuset
- * unless the task has been OOM killed as is marked TIF_MEMDIE.
+ * unless the task has been OOM killed.
  * GFP_KERNEL allocations are not so marked, so can escape to the
  * nearest enclosing hardwalled ancestor cpuset.
  *
@@ -2515,7 +2516,7 @@ static struct cpuset *nearest_hardwall_ancestor(struct cpuset *cs)
  * affect that:
  *	in_interrupt - any node ok (current task context irrelevant)
  *	GFP_ATOMIC   - any node ok
- *	TIF_MEMDIE   - any node ok
+ *	tsk_is_oom_victim - any node ok
  *	GFP_KERNEL   - any node in enclosing hardwalled cpuset ok
  *	GFP_USER     - only nodes in current tasks mems allowed ok.
  */
@@ -2533,7 +2534,7 @@ bool __cpuset_node_allowed(int node, gfp_t gfp_mask)
 	 * Allow tasks that have access to memory reserves because they have
 	 * been OOM killed to get memory anywhere.
 	 */
-	if (unlikely(test_thread_flag(TIF_MEMDIE)))
+	if (unlikely(tsk_is_oom_victim(current)))
 		return true;
 	if (gfp_mask & __GFP_HARDWALL)	/* If hardwall request, stop here */
 		return false;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9ee178ba7b71..df58733ca48e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1899,7 +1899,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
 	 * bypass the last charges so that they can exit quickly and
 	 * free their memory.
 	 */
-	if (unlikely(test_thread_flag(TIF_MEMDIE) ||
+	if (unlikely(tsk_is_oom_victim(current) ||
 		     fatal_signal_pending(current) ||
 		     current->flags & PF_EXITING))
 		goto force;
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index b11977585c7b..e26529edcee3 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -477,7 +477,7 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
 	 *				[...]
 	 *				out_of_memory
 	 *				  select_bad_process
-	 *				    # no TIF_MEMDIE task selects new victim
+	 *				    # no oom victim, selects new victim
 	 *  unmap_page_range # frees some memory
 	 */
 	mutex_lock(&oom_lock);
@@ -1078,7 +1078,7 @@ void pagefault_out_of_memory(void)
 		 * be a racing OOM victim for which oom_killer_disable()
 		 * is waiting for.
 		 */
-		WARN_ON(test_thread_flag(TIF_MEMDIE));
+		WARN_ON(tsk_is_oom_victim(current));
 	}
 
 	mutex_unlock(&oom_lock);
-- 
2.8.1