From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: RFC: Remove swap file support References: <3B472C06.78A9530C@mandrakesoft.com> From: ebiederm@xmission.com (Eric W. Biederman) Date: 14 Jul 2001 00:07:38 -0600 In-Reply-To: <3B472C06.78A9530C@mandrakesoft.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Jeff Garzik Cc: Linux Kernel Mailing List , viro@math.psu.edu, linux-mm@kvack.org List-ID: Jeff Garzik writes: > Since you can make any file into a block device using loop, > is there any value to supporting swap files in 2.5? > > swap files seem like a special case that is no longer necessary... Yes, and no. I'd say what we need to do is update rw_swap_page to use the address space functions directly. With block devices and files going through the page cache in 2.5 that should remove any special cases cleanly. In 2.4 the swap code really hasn't been updated, the old code has only been patched enough to work on 2.4. This adds layers of work that we really don't need to be doing. Removing the extra redirection has the potential to give a small performance boost to swapping. The case to watch out for are deadlocks doing things like using swapfiles on an NFS mount. As you point out we can already do this with the loop back devices so it isn't really a special case. The only new case I can see working are swapfiles with holes in them, or swapfiles that do automatic compression. I doubt those cases are significant improvements but it looks like they will fall out naturally. Eric -- 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/