From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [PULL] vhost: cleanups and fixes Date: Mon, 11 Jun 2018 11:44:05 -0700 Message-ID: References: <20180611192353-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: KVM list , Network Development , Linux Kernel Mailing List , Bjorn Andersson , Andrew Morton , virtualization To: "Michael S. Tsirkin" Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org On Mon, Jun 11, 2018 at 11:32 AM Linus Torvalds wrote: > > So now we apparently do a GFP_KERNEL allocation insider the mm zone > lock, which is broken on just _so_ many levels. Oh, I see the comment about how it doesn't actually do an allocation at all because it's a single-entry. Still too damn ugly to live, and much too fragile. No way in hell do we even _hint_ at a GFP_KERNEL when we're inside a context that can't do any memory allocation at all. Plus I'm not convinced it's a "no allocation" path even despite that comment, because it also does a "dma_map_page()" etc, which can cause allocations to do the dma mapping thing afaik. No? Maybe there's some reason why that doesn't happen either, but basically this whole callchain looks *way* to complicated to be used under a core VM spinlock. Linus