[Pvfs2-developers] kmod no read_inode or iget

[Sam Lang]

On Feb 16, 2008, at 5:46 PM, Pete Wyckoff wrote:

> If anyone is excited about tracking the latest kernels,

Oh, so very.

> pvfs kmod
> breaks on 2.6.25-rc1 and later due to this commit.  It's a bit too
> deep for me to handle.

More config checks and #ifdefs.  We basically can call our read_inode  
directly (which does a getattr to fill in the inode) if its no longer  
part of the super_operations struct.  We were doing this before, but  
through the actual s_ops->read_inode pointer.  Can you try the  
attached patch?  It compiles against the latest tree, but I don't have  
a machine that I can run that kernel on at the moment.

Also, I didn't include configure in this patch so you'll have to ./ 
prepare.

The #ifdefs around the iget4, iget5_locked, etc. code are especially  
nasty.  iget5_locked has been defined in all versions of the 2.6  
kernel, so it would be really nice to just whack those #ifdefs if we  
were to decide not to support 2.4 kernels in future releases.

Thanks,
-sam

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>
>
> 		-- Pete
>
>
> commit 12debc4248a4a7f1873e47cda2cdd7faca80b099
> Author: David Howells <dhowells at redhat.com>
> Date:   Thu Feb 7 00:15:52 2008 -0800
>
> iget: remove iget() and the read_inode() super op as being obsolete
>
> Remove the old iget() call and the read_inode() superblock operation  
> it uses
> as these are really obsolete, and the use of read_inode() does not  
> produce
> proper error handling (no distinction between ENOMEM and EIO when  
> marking an
> inode bad).
>
> Furthermore, this removes the temptation to use iget() to find an  
> inode by
> number in a filesystem from code outside that filesystem.
>
> iget_locked() should be used instead.  A new function is added in an  
> earlier
> patch (iget_failed) that is to be called to mark an inode as bad,  
> unlock it
> and release it should the get routine fail.  Mark iget() and  
> read_inode() as
> being obsolete and remove references to them from the documentation.
>
> Typically a filesystem will be modified such that the read_inode  
> function
> becomes an internal iget function, for example the following:
>
>    void thingyfs_read_inode(struct inode *inode)
>    {
> 	    ...
>    }
>
> would be changed into something like:
>
>    struct inode *thingyfs_iget(struct super_block *sp, unsigned long  
> ino)
>    {
> 	    struct inode *inode;
> 	    int ret;
>
> 	    inode = iget_locked(sb, ino);
> 	    if (!inode)
> 		    return ERR_PTR(-ENOMEM);
> 	    if (!(inode->i_state & I_NEW))
> 		    return inode;
>
> 	    ...
> 	    unlock_new_inode(inode);
> 	    return inode;
>    error:
> 	    iget_failed(inode);
> 	    return ERR_PTR(ret);
>    }
>
> and then thingyfs_iget() would be called rather than iget(), for  
> example:
>
>    ret = -EINVAL;
>    inode = iget(sb, ino);
>    if (!inode || is_bad_inode(inode))
> 	    goto error;
>
> becomes:
>
>    inode = thingyfs_iget(sb, ino);
>    if (IS_ERR(inode)) {
> 	    ret = PTR_ERR(inode);
> 	    goto error;
>    }
>
> Note that is_bad_inode() does not need to be called.  The error  
> returned by
> thingyfs_iget() should render it unnecessary.
>
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