From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Darrick J. Wong" Subject: Re: [PATCH 2/5] vfs: create a generic checking function for FS_IOC_FSSETXATTR Date: Wed, 26 Jun 2019 08:35:42 -0700 Message-ID: <20190626153542.GE5171@magnolia> References: <156151632209.2283456.3592379873620132456.stgit@magnolia> <156151633829.2283456.834142172527987802.stgit@magnolia> <20190626041133.GB32272@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : message-id : references : mime-version : in-reply-to : cc : subject : list-id : list-unsubscribe : list-archive : list-post : list-help : list-subscribe : content-type : content-transfer-encoding : sender; s=corp-2018-07-02; bh=Oq8KDAKUJ1147KjlZXzvsHtnXm/X6h773R0OC3VLRKw=; b=ue5XjCeHdVl6gB4VboMqFtA5XfVBMF6DIGGxNi8oGyyqVMfWYQ6jZF0lC5V26EWcuiwl P6XaLLfwfDlalo/lWdFZ6mZDRR1QJExLB4y1Z/cvOwj0d54zRxU9oo1EWDJbOXbImKE/ 45QAtZrLrion7f1Oyx7D8BrwEeotVa92+0miCOKks465z8rRr2ZkTWZkVCE3/Mh2H1/E /SYwMBuJJAPyV+hd+E4L0MmBCS/JRTx1dPWMgvdtMiqNfYhCU18AEIzOUM0hIDF1cO0G qc2ubo7+Q7I0TYclMOIKlbeNVRiH9YXpx3cRBxIWFvvy3syAS/g0THx5XeMjwjNI2es1 mg== Content-Disposition: inline In-Reply-To: <20190626041133.GB32272@ZenIV.linux.org.uk> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: ocfs2-devel-bounces@oss.oracle.com Errors-To: ocfs2-devel-bounces@oss.oracle.com To: Al Viro Cc: shaggy@kernel.org, jfs-discussion@lists.sourceforge.net, linux-efi@vger.kernel.org, Jan Kara , hch@infradead.org, linux-btrfs@vger.kernel.org, yuchao0@huawei.com, clm@fb.com, adilger.kernel@dilger.ca, matthew.garrett@nebula.com, linux-nilfs@vger.kernel.org, cluster-devel@redhat.com, linux-ext4@vger.kernel.org, josef@toxicpanda.com, reiserfs-devel@vger.kernel.org, dsterba@suse.com, jaegeuk@kernel.org, tytso@mit.edu, ard.biesheuvel@linaro.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, jk@ozlabs.org, jack@suse.com, linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org, ocfs2-devel@oss.oracle.com On Wed, Jun 26, 2019 at 05:11:33AM +0100, Al Viro wrote: > On Tue, Jun 25, 2019 at 07:32:18PM -0700, Darrick J. Wong wrote: > > --- a/fs/btrfs/ioctl.c > > +++ b/fs/btrfs/ioctl.c > > @@ -373,10 +373,9 @@ static int check_xflags(unsigned int flags) > > static int btrfs_ioctl_fsgetxattr(struct file *file, void __user *arg) > > { > > struct btrfs_inode *binode = BTRFS_I(file_inode(file)); > > - struct fsxattr fa; > > - > > - memset(&fa, 0, sizeof(fa)); > > - fa.fsx_xflags = btrfs_inode_flags_to_xflags(binode->flags); > > + struct fsxattr fa = { > > + .fsx_xflags = btrfs_inode_flags_to_xflags(binode->flags), > > + }; > > Umm... Sure, there's no padding, but still - you are going to copy that thing > to userland... How about > > static inline void simple_fill_fsxattr(struct fsxattr *fa, unsigned xflags) > { > memset(fa, 0, sizeof(*fa)); > fa->fsx_xflags = xflags; > } > > and let the compiler optimize the crap out? The v2 series used to do that, but Christoph complained that having a helper for a two-line memset and initialization was silly[1] so now we have this version. I don't mind reinstating it as a static inline helper, but I'd like some input from any of the btrfs developers (or you, Al) about which form is preferred. --D [1] https://lkml.org/lkml/2019/6/25/533