From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: allowed pages in the block later, was Re: [Ext2-devel] [PATCH] ext3: avoid sending down non-refcounted pages From: Arjan van de Ven In-Reply-To: <20051210164736.6e4eaa3f.akpm@osdl.org> References: <20051208180900T.fujita.tomonori@lab.ntt.co.jp> <20051208101833.GM14509@schatzie.adilger.int> <20051208134239.GA13376@infradead.org> <20051210164736.6e4eaa3f.akpm@osdl.org> Content-Type: text/plain Date: Sun, 11 Dec 2005 09:44:04 +0100 Message-Id: <1134290645.2878.4.camel@laptopd505.fenrus.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, open-iscsi@googlegroups.com, ext2-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, michaelc@cs.wisc.edu, fujita.tomonori@lab.ntt.co.jp, Christoph Hellwig List-ID: On Sat, 2005-12-10 at 16:47 -0800, Andrew Morton wrote: > Christoph Hellwig wrote: > > > > The problem we're trying to solve here is how do implement network block > > devices (nbd, iscsi) efficiently. The zero copy codepath in the networking > > layer does need to grab additional references to pages. So to use sendpage > > we need a refcountable page. pages used by the slab allocator are not > > normally refcounted so try to do get_page/pub_page on them will break. > > I don't get it. Doing get_page/put_page on a slab-allocated page should do > the right thing? but it doesn't stop the kfree from freeing the memory; zero copy needs the content of the memory to stay around afterwards, eg it wants to delay the kfree until the data is over the wire, which is an asynchronous event versus the actual send command in a zero-copy situation. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org