From: majianpeng <majianpeng@gmail.com>
Date: Tue, 31 Jul 2012 00:05:44 +0000 (+1000)
Subject: md/raid5: For odirect-write performance, do not set STRIPE_PREREAD_ACTIVE.
X-Git-Tag: v3.6-rc1~21^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=895e3c5c58a80bb9e4e05d9ac38b4f30e0f97d80;p=pandora-kernel.git

md/raid5: For odirect-write performance, do not set STRIPE_PREREAD_ACTIVE.

'sync' writes set both REQ_SYNC and REQ_NOIDLE.
O_DIRECT writes set REQ_SYNC but not REQ_NOIDLE.

We currently assume that a REQ_SYNC request will not be followed by
more requests and so set STRIPE_PREREAD_ACTIVE to expedite the
request.
This is appropriate for sync requests, but not for O_DIRECT requests.

So make the setting of STRIPE_PREREAD_ACTIVE conditional on REQ_NOIDLE
rather than REQ_SYNC.  This is consistent with the documented meaning
of REQ_NOIDLE:

        __REQ_NOIDLE,           /* don't anticipate more IO after this one */

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
---

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