linux-kernel - Re: [PATCH 5/8] exofs: dir_inode and directory operations

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Date:	Tue, 31 Mar 2009 01:04:23 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Boaz Harrosh <bharrosh@...asas.com>
Cc:	Avishay Traeger <avishay@...il.com>, Jeff Garzik <jeff@...zik.org>,
	Evgeniy Polyakov <zbr@...emap.net>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	open-osd <osd-dev@...n-osd.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Subject: Re: [PATCH 5/8] exofs: dir_inode and directory operations

On Wed, 18 Mar 2009 20:08:49 +0200 Boaz Harrosh <bharrosh@...asas.com> wrote:

> implementation of directory and inode operations.
> 
> * A directory is treated as a file, and essentially contains a list
>   of <file name, inode #> pairs for files that are found in that
>   directory. The object IDs correspond to the files' inode numbers
>   and are allocated using a 64bit incrementing global counter.
> * Each file's control block (AKA on-disk inode) is stored in its
>   object's attributes. This applies to both regular files and other
>   types (directories, device files, symlinks, etc.).
> 
>
> ...
>
> +static inline unsigned long dir_pages(struct inode *inode)
> +{
> +	return (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
> +}

Do we need i_size_read() here?  Probably not if it's always called
under i_mutex.  Needs checking and commenting please.

> +static unsigned exofs_last_byte(struct inode *inode, unsigned long page_nr)
> +{
> +	unsigned last_byte = inode->i_size;
> +
> +	last_byte -= page_nr << PAGE_CACHE_SHIFT;

hm.  Strange to left-shift an unsigned long and then copy it to a
smaller type.

Are the types here appropriately chosen?

> +	if (last_byte > PAGE_CACHE_SIZE)
> +		last_byte = PAGE_CACHE_SIZE;
> +	return last_byte;
> +}
> +
> +static int exofs_commit_chunk(struct page *page, loff_t pos, unsigned len)
>
> ...
>

This all looks vaguely familiar :)
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