[PATCH] mm: nommu: set MMF_OOM_SKIP in exit_mmap()

[Alexis Bouzigues via B4 Relay]

From: Alexis Bouzigues <BouziguesAlexis@xxxxxxxxxxxxx>

Commit 212925802454 ("mm: oom: let oom_reap_task and exit_mmap run
concurrently") moved setting MMF_OOM_SKIP from __mmput() into the MMU
exit_mmap(), so it is no longer set when a NOMMU mm is torn down.

As a result, a NOMMU OOM victim that has exited and freed its memory
keeps the OOM killer from selecting another victim until it is reaped.

Set MMF_OOM_SKIP in the NOMMU exit_mmap() once the VMAs are freed, as
the MMU version does.

Fixes: 212925802454 ("mm: oom: let oom_reap_task and exit_mmap run concurrently")
Assisted-by: LLM
Signed-off-by: Alexis Bouzigues <BouziguesAlexis@xxxxxxxxxxxxx>
---
Restore MMF_OOM_SKIP on NOMMU mm teardown, which was lost when it moved
into the MMU-only exit_mmap().
---
 mm/nommu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/nommu.c b/mm/nommu.c
index 498e01ee40b0..913b2a1b5b3b 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1555,6 +1555,7 @@ void exit_mmap(struct mm_struct *mm)
 		delete_vma(mm, vma);
 		cond_resched();
 	}
+	mm_flags_set(MMF_OOM_SKIP, mm);
 	__mt_destroy(&mm->mm_mt);
 	mmap_write_unlock(mm);
 }

---
base-commit: 24a19b953e2a3d0ea5a8c4951a0ab8f32720c907
change-id: 20261013-fix-nommu-exit-mmap-oom-skip-b8e68bf34b6d

Best regards,
-- 
Alexis Bouzigues <BouziguesAlexis@xxxxxxxxxxxxx>