[patch] block: fix queue bounce limit calculation

[Chuck Ebbert]

Queue bounce should start after the max page, not on it.

Signed-off-by: Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx>
---

Could this explain reported slowdown on x86_64 after limit was
changed in 2.6.16.7?

--- 2.6.17.9-64.orig/block/ll_rw_blk.c
+++ 2.6.17.9-64/block/ll_rw_blk.c
@@ -638,11 +638,11 @@ void blk_queue_bounce_limit(request_queu
 	/* Assume anything <= 4GB can be handled by IOMMU.
 	   Actually some IOMMUs can handle everything, but I don't
 	   know of a way to test this here. */
-	if (bounce_pfn < (min_t(u64,0xffffffff,BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
+	if (bounce_pfn <= (min_t(u64,0xffffffff,BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
 		dma = 1;
 	q->bounce_pfn = max_low_pfn;
 #else
-	if (bounce_pfn < blk_max_low_pfn)
+	if (bounce_pfn <= blk_max_low_pfn)
 		dma = 1;
 	q->bounce_pfn = bounce_pfn;
 #endif
-- 
Chuck
-
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