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bh=6jFeCJnJEofDfmaYKz7gwxivXFPa8zGcRtjuIipf8v0=; b=fYLLxfp8GBGqgsSRoXerKvMUPEy8qALfLEsz8RjrhMp8IXqVWGss7LJRYQBfxrM1hO zeUp7CxIT9ib3d8wMIYuiOpVIL3aItJ0qdvbN53v71yyo6fjdxzlb3j44sxWLJukE2Zc 5V3tpIn21Ot8cGFIB3sMsmpVUGIJB040k5rfO6VtyBoZy3uURSbkF2R7j9LGdYnTXGxA NhsD4FCk1tJoSJLqbVO5juQL4LmbtSrl9jcE603/JrGLzLGfiw5XFjh4DEsjoW5cTEyg 45DkfiPKJCnjM9FWWWR8gXAusD7STdLqaTmmgyJ138DAOmVMoY5tINfI8cUNlHYtFZ5d RtmQ== X-Gm-Message-State: AGi0PubxnFLCZSEfxaxWLDU5/C16KoyeHENQ128iuPgd928J+aLfAu2t TZk6EX0ee8EZ1hwvg/hFnK4CO9oZ X-Google-Smtp-Source: APiQypKq0g/iGNP7OID+5quK+Fke1o1LMfZzwoGDk0HrXmqNGo+oWiWJYlua6nM+6Pbr5McP8YFk+Q== X-Received: by 2002:adf:f187:: with SMTP id h7mr5711942wro.331.1586541157972; Fri, 10 Apr 2020 10:52:37 -0700 (PDT) Received: from [192.168.43.32] ([109.126.129.227]) by smtp.gmail.com with ESMTPSA id y7sm4066283wmb.43.2020.04.10.10.52.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Apr 2020 10:52:37 -0700 (PDT) To: Bijan Mottahedeh , axboe@kernel.dk Cc: io-uring@vger.kernel.org References: <1586469817-59280-1-git-send-email-bijan.mottahedeh@oracle.com> <1586469817-59280-2-git-send-email-bijan.mottahedeh@oracle.com> <465d7f4f-e0a4-9518-7b0c-fe908e317720@oracle.com> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <465d7f4f-e0a4-9518-7b0c-fe908e317720@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 10/04/2020 19:54, Bijan Mottahedeh wrote: > >> As I see, this down_read() from the trace is >> down_read(¤t->mm->mmap_sem), where current->mm is set by use_mm() >> just several lines above your change. So, what do you mean by passing? I >> don't see do_madvise() __explicitly__ accepting mm as an argument. > > I think the sequence is: > > io_madvise() > -> do_madvise(NULL, req->work.mm, ma->addr, ma->len, ma->advice) >                     ^^^^^^^^^^^^ >    -> down_read(&mm->mmap_sem) > > I added an assert in do_madvise() for a NULL mm value and hit it running the test. > >> What tree do you use? Extra patches on top? > > I'm using next-20200409 with no patches. I see, it came from 676a179 ("mm: pass task and mm to do_madvise"), which isn't in Jen's tree. I don't think your patch will do, because it changes mm refcounting with extra mmdrop() in io_req_work_drop_env(). That's assuming it worked well before. Better fix then is to make it ```do_madvise(NULL, current->mm, ...)``` as it actually was at some point in the mentioned patch (v5). -- Pavel Begunkov