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 <yong.fan@xxxxxxxxxxxxx>
>>>>>
>>>>> 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@xxxxxxxxxxxxxxxxxx>
>>>>> (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;
>
>
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