linux-kernel - [PATCH] prevent AoE causing cache aliases

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Date:	Thu, 22 Oct 2009 15:22:28 +0100
From:	phorton@...box.co.uk (Peter Horton)
To:	ecashin@...aid.com
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] prevent AoE causing cache aliases

This patch prevents the AoE block driver from creating cache aliases of
page cache pages on machines with virtually indexed caches.

Building kernels on an AT91SAM9G20 board without this patch fails with
segmentation faults after a couple of passes.

Signed-off-by: Peter Horton <zero@...onel-panic.org>

Index: linux-2.6.31/drivers/block/aoe/aoecmd.c
===================================================================
--- linux-2.6.31.orig/drivers/block/aoe/aoecmd.c	2009-09-09 23:13:59.000000000 +0100
+++ linux-2.6.31/drivers/block/aoe/aoecmd.c	2009-10-22 10:24:50.000000000 +0100
@@ -735,6 +735,21 @@
 	part_stat_unlock();
 }
 
+/*
+ * Ensure we don't create aliases in VI caches
+ */
+static inline void
+killalias(struct bio *bio)
+{
+	struct bio_vec *bv;
+	int i;
+
+	if (bio_data_dir(bio) == READ)
+		__bio_for_each_segment(bv, bio, i, 0) {
+			flush_dcache_page(bv->bv_page);
+		}
+}
+
 void
 aoecmd_ata_rsp(struct sk_buff *skb)
 {
@@ -853,8 +868,12 @@
 
 	if (buf && --buf->nframesout == 0 && buf->resid == 0) {
 		diskstats(d->gd, buf->bio, jiffies - buf->stime, buf->sector);
-		n = (buf->flags & BUFFL_FAIL) ? -EIO : 0;
-		bio_endio(buf->bio, n);
+		if (buf->flags & BUFFL_FAIL)
+			bio_endio(buf->bio, -EIO);
+		else {
+			killalias(buf->bio);
+			bio_endio(buf->bio, 0);
+		}
 		mempool_free(buf, d->bufpool);
 	}
 
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