Hi Ian,
I checked the patch for 53.1.4, and my patch is the same as that one:)
will use 53.1.4 if there is no special patches on the under using version.
thanks,
wengang.
Ian Kent wrote:
> On Wed, 2008-01-30 at 11:32 +0800, wengang wang wrote:
>
>> Thanks Ian for your reply.
>>
>> Ian Kent wrote:
>>
>>> On Tue, 2008-01-29 at 17:36 +0800, wengang wang wrote:
>>>
>>>
>>>> Hi experts,
>>>>
>>>> In RHEL kernel 2.6.18-53 and mainline kernel 2.6.24,
>>>>
>>>>
>>> This was a known problem due to a couple of missing patches in the
>>> RHEL-5 kernel revision 53.
>>>
>>>
>>>
>> yes.
>>
>>> I'm not aware of a problem with 2.6.24.
>>>
>>>
>>>
>> yes, there is no problem with 2.6.24.
>> By involving it, I just want to say the code
>> d_instantiate(); //not d_add()
>> is the same.
>>
>>>> in function autofs4_lookup() in fs/autofs4/root.c,
>>>> if dentry is not found in function autofs4_lookup_unhashed(),
>>>> a d_instantiate() is done on the dentry passed as parameter instead of
>>>> d_add().
>>>>
>>>>
>>> d_instantiate is used to delay hashing the dentry until the following
>>> mkdir as this prevents a potential deadlock.
>>>
>>>
>>>
>>>> seems this cause a problem that the first access just after autofs
>>>> started to
>>>> /path/to/<autofsMountPoint>/<nfsMountPoint> fail with the error ENOENT.
>>>>
>>>> If I rolled back to use d_add(), there is no such problem.
>>>> Is this a bug or I omitted something?
>>>>
>>>>
>>> Considering there's virtually no information to go on here I have no
>>> idea but this hasn't been seen to be a problem other than in the RHEL
>>> kernel above.
>>>
>>> You will need to provide a lot more information than this if you want me
>>> to investigate.
>>>
>>>
>>>
>> detail for this problem is:
>> 1) adding a line in /etc/auto.master
>> /topdir /etc/auto.topdir
>> 2) in auto.topdir
>> subdir -fstype=nfs hostname:/path/to/exported/directory
>> 3) /etc/init.d/autofs restart
>> 4) ll /topdir/subdir
>> got NO SUCH DIRECTORY here.
>> by strace, lstat returned ENOENT.
>>
>> according to your
>>
>> This was a known problem due to a couple of missing patches in the
>> RHEL-5 kernel revision 53.
>>
>> I made a patch by comparing RHEL-5 53 kernel with 2.6.24. and seems it
>> solves the problem.
>>
>
> Why, an updated kernel is available for RHEL-5 and has been for some
> time. Try revision 53.1.4.
>
> I started on getting this fixed as soon as I noticed the patches
> missing.
>
>
>> the patch is as below:
>> ----------------------------------------------------------------------------------------------------
>> --- ./fs/autofs4/root.c.orig 2008-01-29 22:20:18.000000000 -0500
>> +++ ./fs/autofs4/root.c 2008-01-29 22:20:47.000000000 -0500
>> @@ -662,10 +662,18 @@
>> * doesn't do the right thing for all system calls, but it should
>> * be OK for the operations we permit from an autofs.
>> */
>> - if (dentry->d_inode && d_unhashed(dentry)) {
>> + if (!oz_mode && d_unhashed(dentry)) {
>> + struct dentry *parent = dentry->d_parent;
>> + struct dentry *new = d_lookup(parent, &dentry->d_name);
>> + if (new != NULL)
>> + dentry = new;
>> + else
>> + dentry = ERR_PTR(-ENOENT);
>> +
>> if (unhashed)
>> dput(unhashed);
>> - return ERR_PTR(-ENOENT);
>> +
>> + return dentry;
>> }
>>
>> if (unhashed)
>> ----------------------------------------------------------------------------------------------------
>>
>> is this patch ok and enough for RHEL-5 kernel revision 53?
>>
>
> Can't remember now but it's the dentry->d_inode -> !oz_mode change that
> is needed for the d_add -> d_instantiate deadlock fix and yes we also
> need to check if someone beat us to the mount with the d_lookup.
>
> However, you really should use the supported updates.
>
> Ian
>
>
>
--
Wengang Wang
Member of Technical Staff
Oracle Asia R&D Center
Open Source Technologies Development
Tel: +86 10 8278 6265
Mobile: +86 13381078925
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