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[209.85.220.65]) by mx.google.com with SMTPS id b51sor2213149ede.8.2019.05.20.14.39.52 for (Google Transport Security); Mon, 20 May 2019 14:39:52 -0700 (PDT) Received-SPF: neutral (google.com: 209.85.220.65 is neither permitted nor denied by best guess record for domain of daniel.vetter@ffwll.ch) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@ffwll.ch header.s=google header.b=HKq8Duys; spf=neutral (google.com: 209.85.220.65 is neither permitted nor denied by best guess record for domain of daniel.vetter@ffwll.ch) smtp.mailfrom=daniel.vetter@ffwll.ch DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=DucpRdkRgOoCBrOy6KiJUJJfWEr/7+ZCIIaJ4AvhfB0=; b=HKq8DuysKW6hx7l8Yig0NV9UpMzIOK98ALTyHYlWExOE6Pc4XsceN9CwZTMEZ+y6cw Cotb3dp0LmPi/TnfsGu9Mc8wGpsj9yCkmJXIekv1AWGWZdRazvo+2R7pulay1RKnKq5x V5EN38iDPb1UvcB2ERZ4RtefPoEDwb5qTXLcw= X-Google-Smtp-Source: APXvYqzzZ2kpVp8haHdbToY3y03B93IZ2fARLhOO1vyR6C1AaG3mgxQcALaUAvLZsqLVYAWfP3KDjg== X-Received: by 2002:a50:b865:: with SMTP id k34mr79563563ede.16.1558388391895; Mon, 20 May 2019 14:39:51 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:569e:0:3106:d637:d723:e855]) by smtp.gmail.com with ESMTPSA id v27sm3285772eja.68.2019.05.20.14.39.50 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 May 2019 14:39:51 -0700 (PDT) From: Daniel Vetter To: DRI Development Cc: Intel Graphics Development , LKML , Linux MM , Daniel Vetter , Andrew Morton , Michal Hocko , =?UTF-8?q?Christian=20K=C3=B6nig?= , David Rientjes , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Paolo Bonzini , Daniel Vetter Subject: [PATCH 1/4] mm: Check if mmu notifier callbacks are allowed to fail Date: Mon, 20 May 2019 23:39:42 +0200 Message-Id: <20190520213945.17046-1-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Just a bit of paranoia, since if we start pushing this deep into callchains it's hard to spot all places where an mmu notifier implementation might fail when it's not allowed to. Inspired by some confusion we had discussing i915 mmu notifiers and whether we could use the newly-introduced return value to handle some corner cases. Until we realized that these are only for when a task has been killed by the oom reaper. An alternative approach would be to split the callback into two versions, one with the int return value, and the other with void return value like in older kernels. But that's a lot more churn for fairly little gain I think. Summary from the m-l discussion on why we want something at warning level: This allows automated tooling in CI to catch bugs without humans having to look at everything. If we just upgrade the existing pr_info to a pr_warn, then we'll have false positives. And as-is, no one will ever spot the problem since it's lost in the massive amounts of overall dmesg noise. v2: Drop the full WARN_ON backtrace in favour of just a pr_warn for the problematic case (Michal Hocko). v3: Rebase on top of Glisse's arg rework. v4: More rebase on top of Glisse reworking everything. Cc: Andrew Morton Cc: Michal Hocko Cc: "Christian König" Cc: David Rientjes Cc: Daniel Vetter Cc: "Jérôme Glisse" Cc: linux-mm@kvack.org Cc: Paolo Bonzini Reviewed-by: Christian König Signed-off-by: Daniel Vetter --- mm/mmu_notifier.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c index ee36068077b6..c05e406a7cd7 100644 --- a/mm/mmu_notifier.c +++ b/mm/mmu_notifier.c @@ -181,6 +181,9 @@ int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range) pr_info("%pS callback failed with %d in %sblockable context.\n", mn->ops->invalidate_range_start, _ret, !mmu_notifier_range_blockable(range) ? "non-" : ""); + if (!mmu_notifier_range_blockable(range)) + pr_warn("%pS callback failure not allowed\n", + mn->ops->invalidate_range_start); ret = _ret; } } -- 2.20.1