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Date:	Sun, 22 Apr 2012 14:51:34 +0200
From:	Bernd Schubert <>
To:	Eric Sandeen <>
CC:,,, Fan Yong <>,, Andreas Dilger <>
Subject: Re: [PATCH 5 2/4] Return 32/64-bit dir name hash according to usage

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!


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