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

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Message-ID: <49D1DCA4.6010306@panasas.com>
Date:	Tue, 31 Mar 2009 12:04:36 +0300
From:	Boaz Harrosh <bharrosh@...asas.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
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 03/31/2009 11:04 AM, Andrew Morton wrote:
> 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;
> 

In that case I might make pcol->pg_first loff_t.

Why is inode->i_index not an loff_t then?
Page-index <=> byte-offset, is done all the time 12 bits does not
make a difference.

>> ...
>>
>> +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;
>> +
>>
>> ...
>>
> 

Thanks
Boaz
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