From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 A715F3B3C06; Wed, 4 Mar 2026 14:43:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772635432; cv=none; b=Lcm9Ho/VPzoz/sS6vtBkPvU61D55lTJqephw7MUnwmsmdAFY4AoTcbFjmhPzL9M2aRdiAU6eV7/RCU0czFExUV5+fPXdLqcz9EFhDtUhsY6hfaP+pYizKV2ruOtWF1RK9jLCSeGcKlvmEBKnzGefO8+fNipxunXYTnLe+ny2cIc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772635432; c=relaxed/simple; bh=aifmAPotaeUEGgUuNKdbDqn1jJtLYUEr8f7yJpRTgtY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=eKcHDg49RbEa8BCRiLyNqPgzNZlQ8DH0srG4BYI3pBnNt/sApkw/KDanD8FPYc/kbQBC9bSu1VTrGjt9iPP4fKwfWkk3HwEENMYmE14WHc5f8bYIpISSIGtt6fzHUSDZkvpLOJ3f42ZO/SCRSpqXOaKdX2HuaRwPjDm9SrXnFXc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=QHFVEnKx; arc=none smtp.client-ip=198.137.202.133 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=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="QHFVEnKx" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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=VcVUA57Ia+lepH55XziYgvy59JWtfGIF7+/AtB87m8A=; b=QHFVEnKxSphuRim6nJ5AcGmLlb SpxJpXgu7dvFkORTjEhgF77N05uUuao6Rra0B84ofOFi1i8bu/4uzLEl5IkiZwzQu/9ofdXn1J1in aLc3I2JHcnuEJPz/VT1RalOGVmLzdMHtDRXF4E/t7uUWVv68SuS1jSUdZsTF6/pAMs2EGLTklrDdX 0cQVe6MhQVryZ9jubR8qiVlyRsNslRlbXwAif1k0NhMGzk5Xvww929JdN9rceO2B1bYNK/AkE9LIg HMxA9APy0M2+f8KIFrEOUPV63hELOaPHETm6HuxcwFXf99rGfAXrlxn7UvlzBwwObL//MJvwK5Tdw F0RCYqDQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vxnS0-0000000HR2h-3jMC; Wed, 04 Mar 2026 14:43:48 +0000 Date: Wed, 4 Mar 2026 06:43:48 -0800 From: Christoph Hellwig To: Sergey Senozhatsky Cc: Jens Axboe , Christoph Hellwig , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC] zram: sleepable async read bio completion Message-ID: References: Precedence: bulk X-Mailing-List: linux-block@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: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Wed, Mar 04, 2026 at 02:15:03PM +0900, Sergey Senozhatsky wrote: > that async read back is not trivial anymore - zram needs to decompress > the page upon bio completion. The problem is that bio completion is > called from atomic context, while zram decompression is sleepable. > So at this point we have to deffer the decompression to a workqueue, > which adds (painful) latency to the read path. We clearly would like > to avoid that workquque offloading. What can we do about it? Nothing. bi_end_io is called from hard/softirq context usually.