linux-kernel - Re: [PATCH] fs/inode: No need to take ->i_lock right after alloc

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Date:	Wed, 08 Jan 2014 11:21:13 +0100
From:	Richard Weinberger <richard@....at>
To:	viro@...iv.linux.org.uk
Cc:	dchinner@...hat.com, hch@....de, eric.dumazet@...il.com,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/inode: No need to take ->i_lock right after alloc_inode()

Am Samstag, 14. Dezember 2013, 21:54:55 schrieb Richard Weinberger:
> In all three cases, new_inode_pseudo(), iget_locked() and iget5_locked(),
> we own the new inode exclusively at this point and therefore taking
> ->i_lock to protect ->i_state/->i_hash against concurrent access is
> superfluous.
> 
> Signed-off-by: Richard Weinberger <richard@....at>
> ---
>  fs/inode.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index 4bcdad3..5f2a735 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -869,9 +869,7 @@ struct inode *new_inode_pseudo(struct super_block *sb)
>  	struct inode *inode = alloc_inode(sb);
> 
>  	if (inode) {
> -		spin_lock(&inode->i_lock);
>  		inode->i_state = 0;
> -		spin_unlock(&inode->i_lock);
>  		INIT_LIST_HEAD(&inode->i_sb_list);
>  	}
>  	return inode;
> @@ -1025,10 +1023,8 @@ struct inode *iget5_locked(struct super_block *sb,
> unsigned long hashval, if (set(inode, data))
>  				goto set_failed;
> 
> -			spin_lock(&inode->i_lock);
>  			inode->i_state = I_NEW;
>  			hlist_add_head(&inode->i_hash, head);
> -			spin_unlock(&inode->i_lock);
>  			inode_sb_list_add(inode);
>  			spin_unlock(&inode_hash_lock);
> 
> @@ -1092,10 +1088,8 @@ struct inode *iget_locked(struct super_block *sb,
> unsigned long ino) old = find_inode_fast(sb, head, ino);
>  		if (!old) {
>  			inode->i_ino = ino;
> -			spin_lock(&inode->i_lock);
>  			inode->i_state = I_NEW;
>  			hlist_add_head(&inode->i_hash, head);
> -			spin_unlock(&inode->i_lock);
>  			inode_sb_list_add(inode);
>  			spin_unlock(&inode_hash_lock);

Any comments on this?

Thanks,
//richard
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