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Sun, 8 Mar 2020 09:59:05 +0000 (GMT) Subject: Re: [PATCH] mm: mmap: show vm_unmapped_area error log To: Matthew Wilcox , Andrew Morton Cc: walken@google.com, bp@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com From: Jaewon Kim Message-ID: <5E64C1D7.3000208@samsung.com> Date: Sun, 8 Mar 2020 18:58:47 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <20200308015802.GD31215@bombadil.infradead.org> Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA01Se0hTcRTu193uruHiOs0OFrluD9psteucXsVZUMQgIaEH6R/abbtt2l7t bpZGZCnaQ7OkIF+0ip74gK3HNCOzsEywIEKK7EUEJVaahWVq2+4k//vOd76P853z+xGY7Bwe R+TbXJzTxloofI7o1gOFSjV435irbmmLZRpam3DmVLWCOe6rRczz9gacedM0JWYmaw4w42MN +FqJvq1uQKL3eN1631Wl3jtSI9E/Pjsu0vt69+t/eBdlSXIs6WaONXJOOWcz2I35NpOO2rg5 b12eNllNq+hUJoWS21grp6PWZ2apNuRbAlkoeSFrcQeoLJbnqdUZ6U6728XJzXbepaM4h9Hi oNWOVTxr5d020yqD3ZpGq9WJ2oByh8U80F0rcjyJ2NfdHFWCBiTHUAQBZBL0TlycfQzNIWSk H4F30C8WihEEFR/vh4tfCM4+rRZPW4bHOnChcRfB25ZKPNiQkUMIpry7gjiazIDuMw9Dhhhy K/j7mgMagsBIK1R0W4M0TibAN09NSCIllXD+4QlREIvIpdBbdTwUbx65HfyNw0jQREFP7ceQ JoJMh3cfXobGYmQ8lN6sx4J5gOzH4fW70+Hd1kN9fWcYR8OXRzfCOA4+V5dLBEMpgqFaHxKK MgQD3iokqDRQVfkME1IroLV9tUAvhrbxRiRMngtff1aKgxIgpXCkXCZIlkPZp5/hYy2EiclP YawHv+9J+HDlGJSWT2AnkbxuxnJ1Mxaq+z/Zg7DrKJZz8FYTx9OOpJkv7EWhz6lk/KijL7ML kQSiIqU7+gy5MjFbyBdZuxAQGBUjPaQMUFIjW1TMOe15TreF47uQNnDvU1jcPIM98NVtrjxa m6jRaJik5JRkrYaaL32frciVkSbWxe3mOAfnnPbNJiLiStCygysUTfLYS9lRc2P2eEqTc1S3 70S+PHrl/ciCTj6z+GKkaXgiLSfh3vcfhdcK1s3am/p5y5IC8/V+itkpGsWe0Wm3ZI/XpLVL cxN6qs589e3ZtFU3TsevTLQb3hb4dZe3XRjtXzP0m/c89RtftFanjvREv7p2clQ1WHy40jv5 N/sPJeLNLK3EnDz7D5wYmhuyAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrHLMWRmVeSWpSXmKPExsWy7bCSvO7LgylxBpfbbSzmrF/DZjGxX9Oi e/NMRovLu+awWdxb85/V4t+kWovfP+awObB77Jx1l91jwaZSj80rtDw2fZrE7nFixm8Wj82n qz0+b5ILYI/isklJzcksSy3St0vgyrh7bCZLwSnOimNrBRsY77J3MXJySAiYSHz8sYeti5GL Q0hgN6PEo+9v2SASMhJvzj9l6WLkALKFJQ4fLoaoec0oMXXGJGaQGmEBO4ljU4+wgtgiAqES V988YYEoamOWeHD5LFiCWSBX4t2zaWBD2QS0Jd4vmAQW5xXQklh4pI8FxGYRUJE43dsNdpGo QITE6nXXmCFqBCVOznwCVsMpYCPx4NFNNpCDmAXUJdbPE4IYLy/RvHU28wRGwVlIOmYhVM1C UrWAkXkVo2RqQXFuem6xYYFRXmq5XnFibnFpXrpecn7uJkZwLGhp7WA8cSL+EKMAB6MSD++O C8lxQqyJZcWVuYcYJTiYlUR4G7WAQrwpiZVVqUX58UWlOanFhxilOViUxHnl849FCgmkJ5ak ZqemFqQWwWSZODilGhg9pzh267I6rH83XfNU2iq5tOkOutoNLZ5Vs9SEdeRWVcxnyapiehJ/ tsOgM2KqeVjD4jz+2ZOnbDc1kd3/t+G9grx9Meu2Z0mq3g6VpoG2TXOK0ueJ7fm048ydk/Pe 1ypPPPLixJLzVXqXL+3r1gioYcxxTIhdcSBJulf8pMbR8vS8Wd1275RYijMSDbWYi4oTAfk2 bKaBAgAA X-CMS-MailID: 20200308095906epcas1p150fec0fb5b86907b09be9104f7171f12 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: SVC_REQ_APPROVE CMS-TYPE: 101P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20200304030211epcas1p4da8cb569947aefb3aad1da039aaabce4 References: <20200304030206.1706-1-jaewon31.kim@samsung.com> <5E605749.9050509@samsung.com> <20200305202443.8de3598558336b1d75afbba7@linux-foundation.org> <5E61EAB6.5080609@samsung.com> <20200307154744.acd523831b45efa8d0fc1dfa@linux-foundation.org> <20200308015802.GD31215@bombadil.infradead.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020년 03월 08일 10:58, Matthew Wilcox wrote: > On Sat, Mar 07, 2020 at 03:47:44PM -0800, Andrew Morton wrote: >> On Fri, 6 Mar 2020 15:16:22 +0900 Jaewon Kim wrote: >>> Even on 64 bit kernel, the mmap failure can happen for a 32 bit task. >>> Virtual memory space shortage of a task on mmap is reported to userspace >>> as -ENOMEM. It can be confused as physical memory shortage of overall >>> system. > But userspace can trigger this printk. We don't usually allow printks > under those circumstances, even ratelimited. Hello thank you your comment. Yes, userspace can trigger printk, but this was useful for to know why a userspace task was crashed. There seems to be still many userspace applications which did not check error of mmap and access invalid address. Additionally in my AARCH64 Android environment, display driver tries to get userspace address to map its display memory. The display driver report -ENOMEM from vm_unmapped_area and but also from GPU related address space. Please let me know your comment again if this debug is now allowed in that userspace triggered perspective. I may change to pr_debug or drop this change. Thank you > >