From: Eric Sandeen <sandeen@redhat.com>
To: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Cc: linux-nfs@vger.kernel.org, linux-ext4@vger.kernel.org,
linux-fsdevel@vger.kernel.org, Fan Yong <yong.fan@whamcloud.com>,
bfields@redhat.com, Andreas Dilger <adilger@whamcloud.com>
Subject: Re: [PATCH 5 2/4] Return 32/64-bit dir name hash according to usage type
Date: Mon, 23 Apr 2012 15:37:06 -0500 [thread overview]
Message-ID: <4F95BD72.6090200@redhat.com> (raw)
In-Reply-To: <4F93FED6.6090505@itwm.fraunhofer.de>
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 <yong.fan@whamcloud.com>
>>>
>>> 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 <bernd.schubert@itwm.fraunhofer.de>
>>> (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.
-Eric
> Cheers,
> Bernd
>
>
>
> --
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next prev parent reply other threads:[~2012-04-23 20:37 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-09 13:21 [PATCH 0/4] [RESEND] 32/64 bit llseek hashes (v5) Bernd Schubert
2012-01-09 13:21 ` [PATCH 5 1/4] Add new FMODE flags: FMODE_32bithash and FMODE_64bithash Bernd Schubert
2012-01-09 13:21 ` [PATCH 5 2/4] Return 32/64-bit dir name hash according to usage type Bernd Schubert
2012-03-05 15:59 ` Ted Ts'o
2012-03-06 0:40 ` Bernd Schubert
2012-03-06 2:28 ` Ted Ts'o
2012-03-06 9:59 ` Bernd Schubert
2012-03-06 15:15 ` Ted Ts'o
2012-03-07 9:01 ` Bernd Schubert
2012-04-20 20:04 ` Eric Sandeen
2012-04-22 12:51 ` Bernd Schubert
2012-04-23 20:37 ` Eric Sandeen [this message]
2012-04-23 20:52 ` Bernd Schubert
2012-04-23 21:22 ` Eric Sandeen
2012-04-23 22:23 ` Eric Sandeen
2012-04-23 22:42 ` Andreas Dilger
2012-04-24 16:10 ` Bernd Schubert
2012-01-09 13:21 ` [PATCH 5 3/4] nfsd_open(): rename 'int access' to 'int may_flags' in nfsd_open() Bernd Schubert
2012-03-06 0:08 ` Ted Ts'o
2012-03-06 2:08 ` J. Bruce Fields
2012-03-06 15:18 ` Ted Ts'o
2012-03-06 15:28 ` J. Bruce Fields
2012-03-09 20:51 ` Ted Ts'o
2012-03-12 15:09 ` Ted Ts'o
2012-03-12 15:49 ` J. Bruce Fields
2012-03-12 22:22 ` J. Bruce Fields
2012-03-13 20:01 ` J. Bruce Fields
2012-03-13 20:03 ` Bernd Schubert
2012-03-13 20:34 ` J. Bruce Fields
2012-03-13 21:09 ` Bernd Schubert
2012-03-13 21:29 ` J. Bruce Fields
2012-03-14 14:32 ` Bernd Schubert
2012-03-14 16:05 ` J. Bruce Fields
2012-03-16 21:22 ` Bernd Schubert
2012-03-19 2:54 ` Ted Ts'o
2012-03-19 20:00 ` J. Bruce Fields
2012-03-20 0:10 ` Ted Ts'o
2012-04-12 20:49 ` J. Bruce Fields
2012-04-12 21:22 ` Bernd Schubert
2012-04-12 21:25 ` J. Bruce Fields
2012-03-13 21:10 ` Ted Ts'o
2012-03-13 21:27 ` J. Bruce Fields
2012-01-09 13:21 ` [PATCH 5 4/4] nfsd: vfs_llseek() with 32 or 64 bit offsets (hashes) Bernd Schubert
2012-01-10 11:27 ` [PATCH 0/4] [RESEND] 32/64 bit llseek hashes (v5) Andreas Dilger
2012-01-11 14:48 ` J. Bruce Fields
2012-01-11 15:31 ` Ted Ts'o
2012-03-05 12:23 ` Bernd Schubert
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