From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Date: Thu, 18 Dec 2008 11:04:14 -0800 Subject: [Cluster-devel] Re: [PATCH 01/24] GFS2: Support for FIEMAP ioctl In-Reply-To: <1229596144.3538.1.camel@localhost.localdomain> References: <1229513423-19105-1-git-send-email-swhiteho@redhat.com> <1229513423-19105-2-git-send-email-swhiteho@redhat.com> <20081217172255.44700cb6.akpm@linux-foundation.org> <1229596144.3538.1.camel@localhost.localdomain> Message-ID: <20081218110414.ac421e1b.akpm@linux-foundation.org> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Thu, 18 Dec 2008 10:29:04 +0000 Steven Whitehouse wrote: > Hi, > > On Wed, 2008-12-17 at 17:22 -0800, Andrew Morton wrote: > > On Wed, 17 Dec 2008 11:30:00 +0000 > > swhiteho at redhat.com wrote: > > > > > +static int gfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > > > + u64 start, u64 len) > > > +{ > > > + struct gfs2_inode *ip = GFS2_I(inode); > > > + struct gfs2_holder gh; > > > + int ret; > > > + > > > + ret = fiemap_check_flags(fieinfo, FIEMAP_FLAG_SYNC); > > > + if (ret) > > > + return ret; > > > + > > > + mutex_lock(&inode->i_mutex); > > > + > > > + ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &gh); > > > + if (ret) > > > + goto out; > > > + > > > + if (gfs2_is_stuffed(ip)) { > > > + u64 phys = ip->i_no_addr << inode->i_blkbits; > > > + u64 size = i_size_read(inode); > > > > It's actually safe to directly access i_size inside i_mutex. Although > > not terribly maintainable. > > > > > I did wonder about that at the time, but I'm not quite sure if you are > suggesting that I should change this now, or leave it as it is? No strong opinion, really. If it's a performance-sensitive path (it isn't) then bypassing i_size_read() might be advantageous. Leaving the i_size_read() there provides some future-safety and sets a good example. It would be an easier decision if the SMP, 32-bit version of i_size_read() wasn't inlined, and tremendously huge :(