[PATCH -next v3 3/3] riscv/vdso: make arch_setup_additional_pages wait for mmap_sem for write killable

[Tong Tiangen]

riscv architectures relying on mmap_sem for write in their
arch_setup_additional_pages. If the waiting task gets killed by the oom killer
it would block oom_reaper from asynchronous address space reclaim and reduce
the chances of timely OOM resolving.  Wait for the lock in the killable mode
and return with EINTR if the task got killed while waiting.

Signed-off-by: Tong Tiangen <tongtiangen at huawei.com>
---
 arch/riscv/kernel/vdso.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
index e7bd92d8749b..b70956d80408 100644
--- a/arch/riscv/kernel/vdso.c
+++ b/arch/riscv/kernel/vdso.c
@@ -77,7 +77,9 @@ int arch_setup_additional_pages(struct linux_binprm *bprm,
 
 	vdso_len = (vdso_pages + VVAR_NR_PAGES) << PAGE_SHIFT;
 
-	mmap_write_lock(mm);
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+
 	vdso_base = get_unmapped_area(NULL, 0, vdso_len, 0, 0);
 	if (IS_ERR_VALUE(vdso_base)) {
 		ret = vdso_base;
-- 
2.18.0.huawei.25