Return-Path: linux-nfs-owner@vger.kernel.org Received: from mx1.redhat.com ([209.132.183.28]:1028 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753591Ab2DWVWx (ORCPT ); Mon, 23 Apr 2012 17:22:53 -0400 Message-ID: <4F95C827.6010207@redhat.com> Date: Mon, 23 Apr 2012 16:22:47 -0500 From: Eric Sandeen MIME-Version: 1.0 To: Bernd Schubert CC: linux-nfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, Fan Yong , bfields@redhat.com, Andreas Dilger Subject: Re: [PATCH 5 2/4] Return 32/64-bit dir name hash according to usage type References: <20120109132137.2616029.76288.stgit@localhost.localdomain> <20120109132148.2616029.68798.stgit@localhost.localdomain> <4F91C15B.6070200@redhat.com> <4F93FED6.6090505@itwm.fraunhofer.de> <4F95BD72.6090200@redhat.com> <4F95C109.1030401@itwm.fraunhofer.de> In-Reply-To: <4F95C109.1030401@itwm.fraunhofer.de> Content-Type: text/plain; charset=UTF-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: On 4/23/12 3:52 PM, Bernd Schubert wrote: > On 04/23/2012 10:37 PM, Eric Sandeen wrote: >> On 4/22/12 7:51 AM, Bernd Schubert wrote: >>> On 04/20/2012 10:04 PM, Eric Sandeen wrote: >>>> On 1/9/12 7:21 AM, Bernd Schubert wrote: >>>>> From: Fan Yong >>>>> >>>>> Traditionally ext2/3/4 has returned a 32-bit hash value from llseek() >>>>> to appease NFSv2, which can only handle a 32-bit cookie for seekdir() >>>>> and telldir(). However, this causes problems if there are 32-bit hash >>>>> collisions, since the NFSv2 server can get stuck resending the same >>>>> entries from the directory repeatedly. >>>>> >>>>> Allow ext4 to return a full 64-bit hash (both major and minor) for >>>>> telldir to decrease the chance of hash collisions. This still needs >>>>> integration on the NFS side. >>>>> >>>>> Patch-updated-by: Bernd Schubert >>>>> (blame me if something is not correct) >>>> >>>> Bernd, I've merged this to ext3. Bruce thought maybe you were working >>>> on the same. Should I send mine? >>> >>> That is perfectly fine with me. >>> >>>> >>>> Also... >>>> >>>>> +/* >>>>> + * ext4_dir_llseek() based on generic_file_llseek() to handle both >>>>> + * non-htree and htree directories, where the "offset" is in terms >>>>> + * of the filename hash value instead of the byte offset. >>>>> + * >>>>> + * NOTE: offsets obtained *before* ext4_set_inode_flag(dir, EXT4_INODE_INDEX) >>>>> + * will be invalid once the directory was converted into a dx directory >>>>> + */ >>>>> +loff_t ext4_dir_llseek(struct file *file, loff_t offset, int origin) >>>> >>>> ext4_llseek() worries about max offset for direct/indirect vs. extent-mapped >>>> files. Do we need to worry about the same thing in this function? >>> >>> Hrmm, I just checked it and I think either is wrong. We only have to >>> care about non-dx directories, so ext4_readdir() applies, which limits >>> filp->f_pos < inode->i_size. >>> Going to send a patch tomorrow. Thanks for spotting this! >> >> The other thing I'm wondering is whether, in light of >> >> ef3d0fd27e90f67e35da516dafc1482c82939a60 vfs: do (nearly) lockless generic_file_llseek >> >> taking the i_mutex in ext4_dir_llseek could be a perf regression vs what was there before? Is there anything about the new function which requires stronger locking? >> >> I may be missing something obvious about the nfs interaction, not sure. >> > > Oh, good point. I was just about to send a small patch, but reading > through the lockless commit will take some time - its already too late > for me for today. Will work on that tomorrow. Thanks again for your review! Sorry it's so late :( -Eric > Cheers, > Bernd > > > > diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c > index b867862..3a4988e2 100644 > --- a/fs/ext4/dir.c > +++ b/fs/ext4/dir.c > @@ -363,7 +363,7 @@ loff_t ext4_dir_llseek(struct file *file, loff_t > offset, int origin) > goto out_err; > > if (!dx_dir) { > - if (offset > inode->i_sb->s_maxbytes) > + if (offset > i_size_read(inode)) > goto out_err; > } else if (offset > ext4_get_htree_eof(file)) > goto out_err; > >