linux-kernel - Re: [PATCH 2/3] proc : no need to initialize proc_inode->fd in proc_get

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Date:	Tue, 4 Sep 2012 15:49:37 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	yan <clouds.yan@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] proc : no need to initialize proc_inode->fd in
 proc_get_inode

On Mon,  3 Sep 2012 22:14:06 +0800
yan <clouds.yan@...il.com> wrote:

> It has been initialized in proc_alloc_inode.
>
> ...

I think what you mean here is that the preceding call to iget_locked()
will call alloc_inode() which will call proc_alloc_inode() which clears
pro_inode.fd.  

And if iget_locked() instead found the inode via find_inode_fast(),
that inode will not have I_NEW set so this change has no effect.

Yes?  Please do spell things out in this level of detail so that others
can check your logic.

> --- a/fs/proc/inode.c
> +++ b/fs/proc/inode.c
> @@ -450,7 +450,6 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
>  		return NULL;
>  	if (inode->i_state & I_NEW) {
>  		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
> -		PROC_I(inode)->fd = 0;
>  		PROC_I(inode)->pde = de;
>  
>  		if (de->mode) {

I provided this changelog:

: proc_get_inode() obtains the inode via a call to iget_locked(). 
: iget_locked() calls alloc_inode() which will call proc_alloc_inode() which
: clears proc_inode.fd, so there is no need to clear this field in
: proc_get_inode().
:
: If iget_locked() instead found the inode via find_inode_fast(), that inode
: will not have I_NEW set so this change has no effect.

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