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 E123A1C32 for ; Wed, 12 Mar 2025 05:47:27 +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=1741758449; cv=none; b=IzlxN2prQSUNNjfW0zzCGPYN4Q2dt+n/zdCFA9V+YdGpooG6WTWtU8MD0+EuoKuAlKSJisJvLu3GFI3mVNcpEGaemm8ZL7Cm+LVEOLxWYIdF7GVF1FRvpqH0vGcMaXIQ7iHQmrOEImuc+8CV8VEnbdebFQIOr79Y3YC4iqZHCzg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741758449; c=relaxed/simple; bh=Hh2h29SUQ+x+D0lILZn4mOfgmnoQUq8RXw0WIv905Fo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LtoFA6flkskxiXYUL2aAHfzp/Xg4g0cseE6Vy//hIHK/dWsldtAhsKCQvBhWgQM65fvq1/zhbbtigJ0/FWWBG8HnZt+d+l0yYKavhOjIjzTVTlewpUuNspSscVnclXQKPSpxVr4rKipzYr3H+Y04UwPyJxUfQosLG7ai1/3BG7g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (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=U/EKia1H; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (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="U/EKia1H" 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=d2aVYY6sXDxPbMJYVjYwVnG/5yAVcTKEEf49trOd3nY=; b=U/EKia1HrMhvMT2TTA74OyHqFy Ur9FgqMiSxT6l4wu6WCRgTCOQd+GVFrSc85Qjhp4PhKm0LEnM4mk4XUviM+eLWc5CZWD6G0D208vb N7bf3fXsToiNCrJSw6n4MibOlxq24zw9z7bFTS++IBDaXtUeEEw9VYTRwSzr4Ag/cufS9C0c6Ewqz MDyMtJto0poA/Q6MM0bU7U09pyKavZ/ADJseb8srav5MbtGX2G/v/OVwttGisVE9mF5kMEoYi6G6b WssQJzTqQasL0Dct/ocH0RAdFD9PENz3N++e3CipkFWijRFm6+EoHe9QshtSZV++B2i3EtJmkwkgl O5W2UgHw==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tsEwB-00000007XcK-0uen; Wed, 12 Mar 2025 05:47:27 +0000 Date: Tue, 11 Mar 2025 22:47:27 -0700 From: Christoph Hellwig To: Jakub Kicinski Cc: "Matthew Wilcox (Oracle)" , Andrew Morton , netdev@vger.kernel.org, Vlastimil Babka , linux-mm@kvack.org, Hannes Reinecke Subject: Re: [PATCH] mm: Decline to manipulate the refcount on a slab page Message-ID: References: <20250310143544.1216127-1-willy@infradead.org> <20250311111511.2531b260@kernel.org> Precedence: bulk X-Mailing-List: netdev@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: <20250311111511.2531b260@kernel.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, Mar 11, 2025 at 11:15:11AM +0100, Jakub Kicinski wrote: > On Mon, 10 Mar 2025 14:35:24 +0000 Matthew Wilcox (Oracle) wrote: > > Long-term, networking needs to stop taking a refcount on the pages that > > it uses and rely on the caller to hold whatever references are necessary > > to make the memory stable. > > TBH I'm not clear on who is going to fix this. > IIRC we already told NVMe people that sending slab memory over sendpage > is not well supported. Plus the bug is in BPF integration, judging by > the stack traces (skmsg is a BPF thing). Joy. slab over sendpage doesn't work because you refuse to take the patches to make it work by transparently falling back to sendmsg. It's a giant pain for all network storage drivers caused by the networking maintainers. The ultimate root cause is the fact that networking messes with the refcounts.