From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4A6F23D411D; Wed, 21 Jan 2026 13:43:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769002991; cv=none; b=ZCXW0RaxUxUfZwsuksbO8h26wuduTqX6+/6nKtYuVXo4NYd+AQ2ldSQfn6X6mzGILcMzWV38iDfRlm0MxumDwRV8/RYIbZMymzYieN3dzHD3mA6Bcds/wfF1PxG5t8KXabivn/KliHeOpc6zM71DUsuajw+1EYQTHOATAYbzQDQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769002991; c=relaxed/simple; bh=BPUSs+DRWFaZUaaeSKV+bFcPdPErDhU0WKpIbS8DUQ0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FtoPUTnWS3RvsgtE0cX7TCdPigZ2JMEnWVctjF+SpppVfTzlOdZlV0opW3mXZVErcDyhP3YlRD+Dnssi6mvdc4QIuU6rtvGLapNakjeZEVY/6FgMncqm00Xv1AmQ/XDcL7zP5UOMPH42hzPr8TAECJOFVHzYvfIJtjn1UHI4vrk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=TB9H8ELB; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="TB9H8ELB" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=BPUSs+DRWFaZUaaeSKV+bFcPdPErDhU0WKpIbS8DUQ0=; b=TB9H8ELBvyJ5o6fkmXBGE4HzcU 9kZIHgbsSNMa8UTK1gr6PLdBQ9DQ+98G4MdYJXDwlKI0PDa6k0DF62m2e+9bxQypK70NS9dRgdjs6 KCXrEmoY3uismyDUFAoTuWFzrMDI0CcIZOIrtnbmF2qrUo9RF6CcjMs8ATBLLdqTWaiHTiMjyMtgO JcxDOomHm7tIVdPaGybioLZHIcpzAd+6cueMVtff2W6tdFhMZDvf8HismZ+B6EnBY59n5StiREDMX eNy2Bzzuz3aqmAfhagGKItK8pqGb+aHz7q+K5L2970v8upiGS/HR81671xwwIG3QyJV4duuxa0Z85 F1SeW3rA==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1viYU8-0000000GPup-13XG; Wed, 21 Jan 2026 13:43:00 +0000 Date: Wed, 21 Jan 2026 13:43:00 +0000 From: Matthew Wilcox To: Jan Kara Cc: Andrew Morton , bernd@bsbernd.com, Joanne Koong , Miklos Szeredi , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] flex_proportions: Make fprop_new_period() hardirq safe Message-ID: References: <20260121112729.24463-2-jack@suse.cz> Precedence: bulk X-Mailing-List: stable@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: <20260121112729.24463-2-jack@suse.cz> On Wed, Jan 21, 2026 at 12:27:30PM +0100, Jan Kara wrote: > Bernd has reported a lockdep splat from flexible proportions code that > is essentially complaining about the following race: [...] > Note that a deadlock like this is only possible if the bdi has > configured maximum fraction of writeout throughput which is very rare > in general but frequent for example for FUSE bdis. To fix this problem > we have to make sure write section of the sequence counter is irqsafe. Ah, that's why we haven't seen it reported before. > CC: stable@vger.kernel.org > Fixes: a91befde3503 ("lib/flex_proportions.c: remove local_irq_ops in fprop_new_period()") > Reported-by: Bernd Schubert > Link: https://lore.kernel.org/all/9b845a47-9aee-43dd-99bc-1a82bea00442@bsbernd.com/ > Signed-off-by: Jan Kara Reviewed-by: Matthew Wilcox (Oracle)