linux-ext4 - Using Cache barriers in lieu of REQ_FLUSH | REQ

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

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.
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html