linux-kernel - [patch 2/6] scsi: warn and avoid creating dma caches if DMA support is disabled

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Message-ID: <alpine.DEB.2.00.1105241650480.29780@chino.kir.corp.google.com>
Date:	Tue, 24 May 2011 16:53:48 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	"James E.J. Bottomley" <James.Bottomley@...e.de>
cc:	Pekka Enberg <penberg@...nel.org>,
	Christoph Lameter <cl@...ux.com>, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [patch 2/6] scsi: warn and avoid creating dma caches if DMA support
 is disabled

__GFP_DMA may not be passed to scsi_{get,put}_host_cmd_pool() if
CONFIG_ZONE_DMA is disabled, which is now possible on x86.  If passed,
emit a warning and return.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 drivers/scsi/scsi.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -359,6 +359,11 @@ EXPORT_SYMBOL(scsi_put_command);
 static struct scsi_host_cmd_pool *scsi_get_host_cmd_pool(gfp_t gfp_mask)
 {
 	struct scsi_host_cmd_pool *retval = NULL, *pool;
+
+#ifndef CONFIG_ZONE_DMA
+	if (WARN_ON_ONCE(gfp_mask & __GFP_DMA))
+		return NULL;
+#endif
 	/*
 	 * Select a command slab for this host and create it if not
 	 * yet existent.
@@ -393,6 +398,10 @@ static void scsi_put_host_cmd_pool(gfp_t gfp_mask)
 {
 	struct scsi_host_cmd_pool *pool;
 
+#ifndef CONFIG_ZONE_DMA
+        if (WARN_ON_ONCE(gfp_mask & __GFP_DMA))
+                return;
+#endif
 	mutex_lock(&host_cmd_pool_mutex);
 	pool = (gfp_mask & __GFP_DMA) ? &scsi_cmd_dma_pool :
 		&scsi_cmd_pool;
--
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