Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030244AbVIILZp (ORCPT ); Fri, 9 Sep 2005 07:25:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030248AbVIILZp (ORCPT ); Fri, 9 Sep 2005 07:25:45 -0400 Received: from ppsw-0.csi.cam.ac.uk ([131.111.8.130]:62618 "EHLO ppsw-0.csi.cam.ac.uk") by vger.kernel.org with ESMTP id S1030244AbVIILZo (ORCPT ); Fri, 9 Sep 2005 07:25:44 -0400 X-Cam-SpamDetails: Not scanned X-Cam-AntiVirus: No virus found X-Cam-ScannerInfo: http://www.cam.ac.uk/cs/email/scanner/ Subject: Re: [PATCH 2/25] NTFS: Allow highmem kmalloc() in ntfs_malloc_nofs() and add _nofail() version. From: Anton Altaparmakov To: Pekka J Enberg Cc: Linus Torvalds , linux-kernel@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net In-Reply-To: References:

<84144f0205090903366454da6@mail.gmail.com> <1126263740.24291.16.camel@imp.csi.cam.ac.uk> Content-Type: text/plain Organization: Computing Service, University of Cambridge, UK Date: Fri, 09 Sep 2005 12:25:38 +0100 Message-Id: <1126265138.24291.21.camel@imp.csi.cam.ac.uk> Mime-Version: 1.0 X-Mailer: Evolution 2.2.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1849 Lines: 43 On Fri, 2005-09-09 at 14:15 +0300, Pekka J Enberg wrote: > On Fri, 9 Sep 2005, Anton Altaparmakov wrote: > > Also note I only use the ntfs_malloc_nofs() wrapper if I have to. If I > > know how much I am allocating or at least know that the maximum is quite > > small, I use kmalloc() directly. It is pretty much only for the runlist > > allocations that I use the wrapper as the runlist is typically small but > > for fragmented files it can grow huge. I have seen runlists consuming > > over 256kiB of ram, without vmalloc that would be a real problem... > > So things like > > rl = ntfs_malloc_nofs(rlsize = PAGE_SIZE); > > should be changed to kmalloc(), right? They could be but I would rather not. What if one day I decide to change how ntfs_malloc_nofs() works? Then it would be needed to carefully go through the whole driver looking for places where kmalloc is used and change those, too. >From a software design point of view you should never mix interfaces when accessing an object if you want clean and maintainable code. And using kmalloc() sometimes and ntfs_malloc_nofs() at other times for the same object would violate that. The wrapper is a static inline so I would assume gcc can optimize away everything when a constant size is passed in like in the example you point out above. Best regards, Anton -- Anton Altaparmakov (replace at with @) Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/