From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f178.google.com (mail-pf1-f178.google.com [209.85.210.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BFD78157A55 for ; Thu, 28 Nov 2024 10:45:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732790720; cv=none; b=str8/JgsY8hMxmHqHrYiMi3kn5QmCvbsxQO1j59Yohdh0nmDKxy3cvYPIbLmeMLwLfdAD4c5EoBJoaPgTBq/sVncbqlhh6CGZCfl7H6LrdqXAnjrpTdEODul5mCJaJXGDjcXuwfoxyofdh3q7L2xrS8g6CnuMmu1Vp3aqzfmwRo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732790720; c=relaxed/simple; bh=ioO9MGJ8RFcxU0OEleMWJT4fb8p5fWpDnbkoHKnnrbI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QG5b7eF+M5a9C4ewQcau8WPi2AAHRBidEjL+pWC1TO9scuScFMVtyFVueHs9R4uLo0rn5n9aJ6mNTdW/ILaOx+vfExYctm38H/QmJJNWGuoRN8syyhdu6+7FDtodB+2sH/h3UxjQAuZ0Ao6MVmA8JodZKC28rv/OJkrZJhrWb2c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org; spf=pass smtp.mailfrom=chromium.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b=QQYoUpnm; arc=none smtp.client-ip=209.85.210.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chromium.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="QQYoUpnm" Received: by mail-pf1-f178.google.com with SMTP id d2e1a72fcca58-7251d20e7f2so740743b3a.0 for ; Thu, 28 Nov 2024 02:45:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1732790718; x=1733395518; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=ra+nPWwa1InJSk6iw9XH2tYRQj9xj6wEO3y2HewRSbM=; b=QQYoUpnmlTCFd1u2im0ISl4NP9yDQ5ZWpms4Rl3qjXIRSe9LhyiVIoC1LV1lEIQceE xNj9/efmvqPTLLmuKlTssKmKKH3o0XCe4ZXFVpMzPiicJu6D8NdhncrTaYYHNVJtsJda zu0w8Uq0uK1q7Zsdo3O5uuGHK3zXnJIOV/aew= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1732790718; x=1733395518; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=ra+nPWwa1InJSk6iw9XH2tYRQj9xj6wEO3y2HewRSbM=; b=OQ/AwF6HoPf2SMVQloxhnSFA8emX6sKXXhmohfPnvhfoUkIzcwzH9q+jrw3nffiraK Qcyua0FgYiwCAe5WzRGFzTQr0lXTLjRW3U6Tdr851epTKPr19QYrXcOPhjWQPm9K1g3t Ywltyit/d5JNdiRmZtVCjJfdV0Mse7XUBMlHk2j//zk+ZmklIWr+GVUWrlDKMwJKlxxx vCQhseeaakRjV+rKwdEn01ZLoFLPRlm9rEAsP9qLLHtwKDQTmy+6EnBQvGJrLSkD8POP eAcoPnfr/NFleqalwqt2CXFNO6XXk0dBpH8G35UunFcaQ6snqnbBvr3ue9OC4Zk23rDp 5nTA== X-Forwarded-Encrypted: i=1; AJvYcCVWj7I8DsVLxlLlYFpZI7rmO21ojKBtTZvTD9/4Ihewdt+O+WWGniqpGmGVhEnCXkvhS9owCVTt/EYTLnQ=@vger.kernel.org X-Gm-Message-State: AOJu0YzyWk4zFGunoSVhWAps8iNVYOSNoF1sDZTL9avF8HbE1ruRv94T s3+ol6vWiEbpfw6J7zfG3bThuU0/n7cjeSuO0VPQ3pWlY7Vs5UqfOz3uKpMNFA== X-Gm-Gg: ASbGncuI0hfgj/NGacrM50JNy+x9Pg0T57i5VYNf5MFrRiSaT1WqFR0VnIGHSFhN2+g Yq7XYOnphXLtlcEBqK94GGOshk+YpjHVa1YP/dHmKR0HzYXFFcCUbiQtjBRRYVdwh3wEFWqgzF8 nfCcs6ESwvpxb4GgJ4TO38R5AqWrMisL2BqXZ7RUiOTg4lH9CKKVcu8ZG0tYzNh8v630wZ5Ubw3 /t0TMBrgty68Bg+6RyxFrPGdZwYaBSyuyqbvPD4BaMYXXSF4O29Cw== X-Google-Smtp-Source: AGHT+IEIQGcWD1j2zqd9Z7eniwrjeF+M26Y7kRStHyL6ZBIdiQ4WELp7bX7g43tSEb4fQEtQElvAIw== X-Received: by 2002:a05:6a00:228b:b0:724:d511:3d60 with SMTP id d2e1a72fcca58-7252ffc9399mr9280355b3a.2.1732790718058; Thu, 28 Nov 2024 02:45:18 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:e87e:5233:193f:13e1]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72541848b4dsm1238011b3a.186.2024.11.28.02.45.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Nov 2024 02:45:17 -0800 (PST) Date: Thu, 28 Nov 2024 19:45:14 +0900 From: Sergey Senozhatsky To: Bernd Schubert Cc: Sergey Senozhatsky , Miklos Szeredi , Tomasz Figa , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: fuse: fuse semantics wrt stalled requests Message-ID: <20241128104514.GC10431@google.com> References: <20241128035401.GA10431@google.com> <45da8248-d694-4220-a120-3d85a463c0cf@fastmail.fm> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45da8248-d694-4220-a120-3d85a463c0cf@fastmail.fm> On (24/11/28 11:29), Bernd Schubert wrote: > On 11/28/24 04:54, Sergey Senozhatsky wrote: > > Hello Miklos, > > > > A question: does fuse define any semantics for stalled requests handling? > > > > We are currently looking at a number of hung_task watchdog crashes with > > tasks waiting forever in d_wait_lookup() for dentries to lose PAR_LOOKUP > > state, and we suspect that those dentries are from fuse mount point > > (we also sometimes see hung_tasks in fuse_lookup()->fuse_simple_request()). > > Supposedly (a theory) some tasks are in request_wait_answer() under > > PAR_LOOKUP, and the rest of tasks are waiting for them to finish and clear > > PAR_LOOKUP bit. > > > > request_wait_answer() waits indefinitely, however, the interesting > > thing is that it uses wait_event_interruptible() (when we wait for > > !fc->no_interrupt request to be processed). What is the idea behind > > interruptible wait? Is this, may be, for stall requests handling? > > Does fuse expect user-space to watchdog or monitor its processes/threads > > that issue syscalls on fuse mount points and, e.g., SIGKILL stalled ones? > > > > To make things even more complex, in our particular case fuse mount > > point mounts a remote google driver, so it become a network fs in > > some sense, which adds a whole new dimension of possibilities for > > stalled/failed requests. How those are expected to be handled? Should > > fuse still wait indefinitely or would it make sense to add a timeout > > to request_wait_answer() and FR_INTERRUPTED timeout-ed requests? > > > > Please see here > > https://lore.kernel.org/all/20241114191332.669127-1-joannelkoong@gmail.com/ Thanks for the pointers!