linux-kernel - Re: [PATCH 15/18] fs: icache remove inode

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Date:	Wed, 13 Oct 2010 09:42:17 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Dave Chinner <david@...morbit.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/18] fs: icache remove inode_lock

> +[mandatory]
> +	inode_lock is gone, replaced by fine grained locks. See fs/inode.c
> +for details of what locks to replace inode_lock with in order to protect
> +particular things. Most of the time, a filesystem only needs ->i_lock, which
> +protects *all* the inode state and its membership on lists that was
> +previously protected with inode_lock.


Actually in general filesystem don't need to know anything of the inode
locking, I suspect we could just drop this blurb.  inode_lock wasn't
exported so the only thing that changed for filesystems is that the
atomic i_count counter was replaced by i_ref.

Maybe replace the above with:

[mandatory]
	The i_count field in the inode is replaced with i_ref, which is
	a regular integer instead of an atomic_t.  Filesystems should
	not manipulate it directly but use helpers like iref, igrab
	and iput.

And btw, Documentation/filesystems/vfs.txt and include/linux/fs.h
still mention i_count, and arch/powerpc/platforms/cell/spufs/file.c
still has a reference to it in code.

> @@ -1261,9 +1234,7 @@ int sync_inode(struct inode *inode, struct writeback_control *wbc)
>  {
>  	int ret;
>  
> -	spin_lock(&inode_lock);
>  	ret = writeback_single_inode(inode, wbc);
> -	spin_unlock(&inode_lock);
>  	return ret;
>  }
>  EXPORT_SYMBOL(sync_inode);

At this point writeback_single_inode and sync_inode are the same.
I'd just rename writeback_single_inode to sync_inode and kill the
wrapper.

>   * Lock orders
> - * inode_lock
>   *   inode hash bucket lock
>   *     inode->i_lock
>   *
> - * inode_lock
>   *   sb inode lock
>   *     inode_lru_lock
>   *       wb->b_lock

reindent?


Otherwise looks good,


Reviewed-by: Christoph Hellwig <hch@....de>
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