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Subject: [PATCH 4/5] proc: use down_read_killable for /proc/pid/clear_refs
From:   Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
To:     linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org
Cc:     Cyrill Gorcunov <gorcunov@gmail.com>,
        Kirill Tkhai <ktkhai@virtuozzo.com>,
        Al Viro <viro@zeniv.linux.org.uk>
Date:   Wed, 15 May 2019 11:41:21 +0300
Message-ID: <155790968147.1319.10247444846354273332.stgit@buzz>
In-Reply-To: <155790967258.1319.11531787078240675602.stgit@buzz>
References: <155790967258.1319.11531787078240675602.stgit@buzz>
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Replace the only unkillable mmap_sem lock in clear_refs_write.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
 fs/proc/task_mmu.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 78bed6adc62d..7f84d1477b5b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1140,7 +1140,10 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 			goto out_mm;
 		}
 
-		down_read(&mm->mmap_sem);
+		if (down_read_killable(&mm->mmap_sem)) {
+			count = -EINTR;
+			goto out_mm;
+		}
 		tlb_gather_mmu(&tlb, mm, 0, -1);
 		if (type == CLEAR_REFS_SOFT_DIRTY) {
 			for (vma = mm->mmap; vma; vma = vma->vm_next) {