Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755977AbZGFKft (ORCPT ); Mon, 6 Jul 2009 06:35:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753964AbZGFKfj (ORCPT ); Mon, 6 Jul 2009 06:35:39 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:56342 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751937AbZGFKfj (ORCPT ); Mon, 6 Jul 2009 06:35:39 -0400 Date: Mon, 6 Jul 2009 06:35:40 -0400 From: Christoph Hellwig To: Nick Piggin Cc: Christoph Hellwig , Jan Kara , LKML , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 02/11] vfs: Add better VFS support for page_mkwrite when blocksize < pagesize Message-ID: <20090706103539.GA2611@infradead.org> References: <1245088797-29533-1-git-send-email-jack@suse.cz> <1245088797-29533-3-git-send-email-jack@suse.cz> <20090625161753.GB30755@wotan.suse.de> <20090625174754.GA21957@infradead.org> <20090626084225.GA12201@wotan.suse.de> <20090630173716.GA3150@infradead.org> <20090702072225.GC2714@wotan.suse.de> <20090704151801.GA19682@infradead.org> <20090706090804.GM2714@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090706090804.GM2714@wotan.suse.de> User-Agent: Mutt/1.5.18 (2008-05-17) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2287 Lines: 65 On Mon, Jul 06, 2009 at 11:08:04AM +0200, Nick Piggin wrote: > OK, hmm, but I wonder -- most of the time do_truncate will need to > call notify_change anyway, so I wonder if avoiding the double > indirection saves us anything? (It requires 2 indirect calls either > way). And if we call ->setsize from ->setattr, then a filesystem > which implements its own ->setattr could avoid one of those indirect > calls. Not so if do_truncate has to call ->setattr then ->setsize. I don't quite understand what you mean here. In the end there should be one single indirect call, ->setsize (or whatever it's called by then). In the first round we'd split up a helper just for size updates from notify_change, ala: int vfs_truncate(struct dentry *dentry, loff_t size, int flags, file) { int error; error = security_inode_truncate(dentry, size, flags, file); if (error) return error; if (inode->i_op->setsize) { inode->i_op->setsize(dentry, size, flags, file); } else { <... built up iattr here ...> if (inode->i_op->setattr) { down_write(&dentry->d_inode->i_alloc_sem); error = inode->i_op->setattr(dentry, attr); up_write(&dentry->d_inode->i_alloc_sem); } else { down_write(&dentry->d_inode->i_alloc_sem); error = inode_setattr(inode, attr); up_write(&dentry->d_inode->i_alloc_sem); } } if (!error) fsnotify_truncate(dentry, size, flags); return error; } One all filesistem are converted to have a setsize method (either their own or simple_setsize) the !inode->i_op->setsize case can go away. Note that the above variant moves taking i_alloc_sem into ->setsize as it's not required for most filesystems (I think only extN need for O_DIRECT). Also the above doesn't deal with killing the SUID/SGID bits yet, we'll need some good way for that. Actually it might be better to just pass the iattr to ->setsize to so we can have the parsing for those arguments once, and that filesystems can re-use parts of their ->setattr for ->setsize if it's complex enough (timestamp updates and suid/sgid killing) -- 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/