How to get the inode - no path_lookup

[Rohan Puri]

On Thu, Aug 9, 2012 at 8:45 AM, Rishi Agrawal <rishi.b.agrawal at gmail.com>wrote:

>
>
> On Wed, Aug 8, 2012 at 12:46 PM, Rohan Puri <rohan.puri15 at gmail.com>wrote:
>
>>
>>
>> On Tue, Aug 7, 2012 at 8:11 PM, Rishi Agrawal <rishi.b.agrawal at gmail.com>wrote:
>>
>>> Hi All,
>>>
>>>
>>> I had a module which used the path_lookup function to print the details
>>> of any file's inode. I now want to rewrite that module in order to show
>>> some juniors how to write some code in kernel.
>>>
>>> I am using 3.4.6 kernel, I tried finding out path_lookup but google
>>> showed that it has been removed.
>>>
>>> I tried the following code then which did not work
>>>
>>> .
>>> .
>>> .
>>> dentry = kern_path_create(AT_FDCWD, filename, &path, 1);
>>>
>>> if (IS_ERR(dentry)) {
>>>               printk("Failed to obtain the dentry");
>>>                return;
>>>        }
>>>
>>> its not returning dentry
>>>
>>> I again tried after seeing the implementation of vfs_stat function
>>>
>>> user_path_at(AT_FDCWD, filename, lookup_flags, &path);
>>>
>>> but this also fails.
>>>
>>>
>>> I am using a proc interface to pass the filename, and copying the
>>> filename into a kernel buffer.
>>>
>>> How can I get a copy of vfs inode for a file name.
>>>
>>>
>>> Need to use vfs_path_lookup for this, present in fs/namei.c file, which
>> would give you filled nameidata nd that contais inodes pointer.
>>
>>> --
>>> Regards,
>>> Rishi Agrawal
>>>
>>>
>>> _______________________________________________
>>> Kernelnewbies mailing list
>>> Kernelnewbies at kernelnewbies.org
>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>
>>>
>> - Rohan
>>
>
> vfs_path_lookup needs a dentry/mountpoint for the current path.
>
> How will I get those.
>
>
> /**
>  * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
>  * @dentry:  pointer to dentry of the base directory
>  * @mnt: pointer to vfs mount of the base directory
>  * @name: pointer to file name
>  * @flags: lookup flags
>  * @path: pointer to struct path to fill
>  */
>
>
> --
> Regards,
> Rishi Agrawal
>
> If you dont have vfsmount's ptr, then you can make use of kern_path api
with the LOOKUP_FOLLOW as second parameter. This will return the struct
path ptr which contains vfsmount and the dentry's ptr. Now the dentry's ptr
will contain the inode that you require.

- Rohan
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