Re: [PATCH v2] read-modify-write page updating

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On Fri, Jul 10, 2009 at 11:57:02AM -0400, Peter Staubach wrote:
> Trond Myklebust wrote:
>> On Thu, 2009-07-09 at 10:12 -0400, Peter Staubach wrote:
>>
>>   
>>> Signed-off-by: Peter Staubach <staubach@xxxxxxxxxx>
>>>     
>>
>> Please could you send such patches as inline, rather than as
>> attachments. It makes it harder to comment on the patch contents...
>>
>>   
>
> I will investigate how to do this.

See Documentation/email-clients.txt.  (It has an entry for Thunderbird,
for example.)

--b.

>
>>> +static int nfs_want_read_modify_write(struct file *file, struct page *page,
>>> +			loff_t pos, unsigned len)
>>> +{
>>> +	unsigned int pglen = nfs_page_length(page);
>>> +	unsigned int offset = pos & (PAGE_CACHE_SIZE - 1);
>>> +	unsigned int end = offset + len;
>>> +
>>> +	if ((file->f_mode & FMODE_READ) &&	/* open for read? */
>>> +	    !PageUptodate(page) &&		/* Uptodate? */
>>> +	    !PageDirty(page) &&			/* Dirty already? */
>>> +	    !PagePrivate(page) &&		/* i/o request already? */
>>>     
>>
>> I don't think you need the PageDirty() test. These days we should be
>> guaranteed to always have PagePrivate() set whenever PageDirty() is
>> (although the converse is not true). Anything else would be a bug...
>>
>>   
>
> Okie doke.  It seemed to me that this should be true, but it was
> safer to leave both tests.
>
> I will remove that PageDirty test, retest, and then send another
> version of the patch.  I will be out next week, so it will take a
> couple of weeks.
>
>    Thanx...
>
>       ps
>
>>> +	    pglen &&				/* valid bytes of file? */
>>> +	    (end < pglen || offset))		/* replace all valid bytes? */
>>> +		return 1;
>>> +	return 0;
>>> +}
>>> +
>>>     
>>
>>   
>
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