From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: [rfc][patch] mm, fs: warn on missing address space operations Date: Mon, 22 Mar 2010 11:55:08 +0000 Message-ID: <20100322115508.GE30031@ZenIV.linux.org.uk> References: <20100322053937.GA17637@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org To: Nick Piggin Return-path: Content-Disposition: inline In-Reply-To: <20100322053937.GA17637@laptop> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Mon, Mar 22, 2010 at 04:39:37PM +1100, Nick Piggin wrote: > It's ugly and lazy that we do these default aops in case it has not > been filled in by the filesystem. > > A NULL operation should always mean either: we don't support the > operation; we don't require any action; or a bug in the filesystem, > depending on the context. > > In practice, if we get rid of these fallbacks, it will be clearer > what operations are used by a given address_space_operations struct, > reduce branches, reduce #if BLOCK ifdefs, and should allow us to get > rid of all the buffer_head knowledge from core mm and fs code. > > We could add a patch like this which spits out a recipe for how to fix > up filesystems and get them all converted quite easily. Um. Seeing that part of that is for methods absent in mainline (->release(), ->sync()), I'd say that making it mandatory at that point is a bad idea. As for the rest... We have 90 instances of address_space_operations in the kernel. Out of those: 28 have ->releasepage != NULL 27 have ->set_page_dirty != NULL 25 have ->invalidatepage != NULL So I'm not even sure that adding that much boilerplate makes sense. -- 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