Return-Path: linux-nfs-owner@vger.kernel.org Received: from out3-smtp.messagingengine.com ([66.111.4.27]:45198 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753585Ab2DWUwe (ORCPT ); Mon, 23 Apr 2012 16:52:34 -0400 Message-ID: <4F95C109.1030401@itwm.fraunhofer.de> Date: Mon, 23 Apr 2012 22:52:25 +0200 From: Bernd Schubert MIME-Version: 1.0 To: Eric Sandeen 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> In-Reply-To: <4F95BD72.6090200@redhat.com> Content-Type: text/plain; charset=UTF-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: 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! 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;