This patch prevents potential host_no allocation race and
recycle unused host numbers by using idr.
Signed-off-by: Akinobu Mita <mita@xxxxxxxxxxxxxxxx>
--- 2.6-rc/drivers/scsi/hosts.c.orig 2005-12-14 15:22:11.000000000 +0900
+++ 2.6-rc/drivers/scsi/hosts.c 2005-12-14 16:36:15.000000000 +0900
@@ -31,6 +31,7 @@
#include <linux/completion.h>
#include <linux/transport_class.h>
#include <linux/platform_device.h>
+#include <linux/idr.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_host.h>
@@ -39,9 +40,9 @@
#include "scsi_priv.h"
#include "scsi_logging.h"
-
-static int scsi_host_next_hn; /* host_no for next new host */
-
+#define MAX_HOST_NO 0xffff
+static DEFINE_IDR(host_no_idr);
+static DEFINE_SPINLOCK(host_no_lock);
static void scsi_host_cls_release(struct class_device *class_dev)
{
@@ -259,6 +260,10 @@ static void scsi_host_dev_release(struct
struct Scsi_Host *shost = dev_to_shost(dev);
struct device *parent = dev->parent;
+ spin_lock(&host_no_lock);
+ idr_remove(&host_no_idr, shost->host_no);
+ spin_unlock(&host_no_lock);
+
if (shost->ehandler)
kthread_stop(shost->ehandler);
if (shost->work_q)
@@ -290,6 +295,8 @@ struct Scsi_Host *scsi_host_alloc(struct
struct Scsi_Host *shost;
gfp_t gfp_mask = GFP_KERNEL;
int rval;
+ int index;
+ int error;
if (sht->unchecked_isa_dma && privsize)
gfp_mask |= __GFP_DMA;
@@ -322,7 +329,18 @@ struct Scsi_Host *scsi_host_alloc(struct
init_MUTEX(&shost->scan_mutex);
- shost->host_no = scsi_host_next_hn++; /* XXX(hch): still racy */
+host_no_retry:
+ if (!idr_pre_get(&host_no_idr, GFP_KERNEL))
+ goto fail_kfree;
+ spin_lock(&host_no_lock);
+ error = idr_get_new(&host_no_idr, NULL, &index);
+ spin_unlock(&host_no_lock);
+ if (error == -EAGAIN)
+ goto host_no_retry;
+ if ((index >= MAX_HOST_NO) || error)
+ goto fail_kfree;
+
+ shost->host_no = index;
shost->dma_channel = 0xff;
/* These three are default values which can be overridden */
-
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