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Date:	Tue, 15 Sep 2015 16:17:46 -0700
From:	Nikhilesh Reddy <reddyn@...eaurora.org>
To:	Theodore Ts'o <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Using Cache barriers in lieu of REQ_FLUSH | REQ_FUA for emmc 5.1
 (jdec spec JESD84-B51)

Hi

The eMMC 5.1 spec defines cache "barrier" capability of the eMMC device 
as defined in JESD84-B51

I was wondering if there were any downsides to replacing the 
WRITE_FLUSH_FUA	 with the cache barrier?

I understand that REQ_FLUSH is used to ensure that the current cache be 
flushed to prevent any reordering but I dont seem to be clear on why
REQ_FUA is used.
Can someone please help me understand this part?

But as far as I understand it ... the cache barriers can be used to 
replace all the flush requests.

Please let me know if there is any downside to this ?

I know there there was a big decision in 2010 
https://lwn.net/Articles/400541/
and http://lwn.net/Articles/399148/
to remove the software based barrier support... but with the hardware 
supporting "barriers" is there a downside to using them to replace the 
flushes?
-- 
Thanks
Nikhilesh Reddy

Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.
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