linux-kernel - Re: [PATCH 4/8 ver5] exofs: address_space

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Date:	Tue, 31 Mar 2009 01:04:20 -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>,
	Marcin Slusarz <marcin.slusarz@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Subject: Re: [PATCH 4/8 ver5] exofs: address_space_operations

On Sun, 22 Mar 2009 15:58:46 +0200 Boaz Harrosh <bharrosh@...asas.com> wrote:

> 
> OK Now we start to read and write from osd-objects. We try to
> collect at most contiguous pages as possible in a single write/read.
> The first page index is the object's offset.
> 
> TODO:
>    In 64-bit a single bio can carry at most 128 pages.
>    Add support of chaining multiple bios
> 
>
> ...
>
> +static int write_exec(struct page_collect *pcol)
> +{
> +	struct exofs_i_info *oi = exofs_i(pcol->inode);
> +	struct osd_obj_id obj = {pcol->sbi->s_pid,
> +					pcol->inode->i_ino + EXOFS_OBJ_OFF};
> +	struct osd_request *or = NULL;
> +	struct page_collect *pcol_copy = NULL;
> +	loff_t i_start = pcol->pg_first << PAGE_CACHE_SHIFT;

bug.  On 32-bit this shift will overflow prior to getting promoted to
64-bit.  Do:

	loff_t i_start = (loff_t)pcol->pg_first << PAGE_CACHE_SHIFT;

>
> ...
>
> +static int writepage_strip(struct page *page,
> +			   struct writeback_control *wbc_unused, void *data)

Some of these functions could do with some comments explaining why they exist.

> +	struct page_collect *pcol = data;
> +	struct inode *inode = pcol->inode;
> +	struct exofs_i_info *oi = exofs_i(inode);
> +	loff_t i_size = i_size_read(inode);
> +	pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
> +	size_t len;
> +	int ret;
> +
>
> ...
>

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