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Wong" To: Al Viro Subject: Re: [PATCH 2/5] vfs: create a generic checking function for FS_IOC_FSSETXATTR 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-Disposition: inline In-Reply-To: <20190626041133.GB32272@ZenIV.linux.org.uk> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9299 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906260182 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190626_083603_855384_ECDCB762 X-CRM114-Status: GOOD ( 14.29 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org 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 ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/