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[79.178.32.166]) by smtp.gmail.com with ESMTPSA id v4sm49928180wrw.42.2020.12.27.03.18.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 27 Dec 2020 03:18:58 -0800 (PST) Date: Sun, 27 Dec 2020 06:18:55 -0500 From: "Michael S. Tsirkin" To: Willem de Bruijn Cc: wangyunjian , Network Development , Jason Wang , virtualization@lists.linux-foundation.org, "Lilijun (Jerry)" , chenchanghu , xudingke , "huangbin (J)" Subject: Re: [PATCH net] tun: fix return value when the number of iovs exceeds MAX_SKB_FRAGS Message-ID: <20201227061540-mutt-send-email-mst@kernel.org> References: <1608810533-8308-1-git-send-email-wangyunjian@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Dec 24, 2020 at 10:56:16AM -0500, Willem de Bruijn wrote: > On Thu, Dec 24, 2020 at 6:51 AM wangyunjian wrote: > > > > From: Yunjian Wang > > > > Currently the tun_napi_alloc_frags() function returns -ENOMEM when the > > number of iovs exceeds MAX_SKB_FRAGS + 1. However this is inappropriate, > > we should use -EMSGSIZE instead of -ENOMEM. > > > > Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver") > > Signed-off-by: Yunjian Wang > > Acked-by: Willem de Bruijn > > It might be good to explain why the distinction matters: one denotes a > transient failure that the caller (specifically vhost_net) can retry, > the other a persistent failure due to bad packet geometry that should > be dropped. It would be good to have a definition of what constitutes a transient failure. At the moment there's a proposed patch to vhost that tests for err == -EAGAIN || err == -ENOMEM || err == -ENOBUFS and we'll likely add EIO to that. Alternatively, I'm inclined to say any invalid input should just return EINVAL except maybe for memory access errors which traditionally are EFAULT. Then vhost can handle any failure except EINVAL and EFAULT as transient. -- MST