Re: [BK PATCH] SCSI host num allocation improvement

Andrew Morton
2004-02-27T22:28:54Z

Mike Anderson <andmike@us.ibm.com> wrote:
>
> Ben Collins [bcollins@debian.org] wrote:
> > static void scsi_host_cls_release(struct class_device *class_dev)
> > {
> > + down(&host_num_lock);
> > + idr_remove(&allocated_hosts, class_to_shost(class_dev)->host_no);
> > + up(&host_num_lock);
> > put_device(&class_to_shost(class_dev)->shost_gendev);
> > }
> >
>
> Should the idr_remove be done in scsi_host_dev_release instead? We
> really should not make this number available until everyone is done with
> this host.

Beats me. If you're right, this is the patch.

diff -puN drivers/scsi/hosts.c~scsi-host-allocation-fix drivers/scsi/hosts.c
--- 25/drivers/scsi/hosts.c~scsi-host-allocation-fix Fri Feb 27 14:11:47 2004
+++ 25-akpm/drivers/scsi/hosts.c Fri Feb 27 14:29:01 2004
@@ -30,6 +30,7 @@
#include <linux/list.h>
#include <linux/completion.h>
#include <linux/unistd.h>
+#include <linux/idr.h>

#include <scsi/scsi_host.h>
#include "scsi.h"
@@ -37,9 +38,26 @@
#include "scsi_priv.h"
#include "scsi_logging.h"

+static DECLARE_MUTEX(host_num_lock);
+static struct idr allocated_hosts;

-static int scsi_host_next_hn; /* host_no for next new host */
+static int alloc_host_no(void)
+{
+ int ret = -ENOMEM;
+
+ down(&host_num_lock);
+ if (idr_pre_get(&allocated_hosts, GFP_KERNEL))
+ ret = idr_get_new(&allocated_hosts, NULL);
+ up(&host_num_lock);
+ return ret;
+}

+static void free_host_no(int host_no)
+{
+ down(&host_num_lock);
+ idr_remove(&allocated_hosts, host_no);
+ up(&host_num_lock);
+}

static void scsi_host_cls_release(struct class_device *class_dev)
{
@@ -163,9 +181,11 @@ static void scsi_host_dev_release(struct
*/
if (parent)
put_device(parent);
+ free_host_no(shost->host_no);
kfree(shost);
}

+
/**
* scsi_host_alloc - register a scsi host adapter instance.
* @sht: pointer to scsi host template
@@ -184,6 +204,7 @@ struct Scsi_Host *scsi_host_alloc(struct
struct Scsi_Host *shost;
int gfp_mask = GFP_KERNEL, rval;
DECLARE_COMPLETION(complete);
+ int host_no;

if (sht->unchecked_isa_dma && privsize)
gfp_mask |= __GFP_DMA;
@@ -214,7 +235,6 @@ struct Scsi_Host *scsi_host_alloc(struct

init_MUTEX(&shost->scan_mutex);

- shost->host_no = scsi_host_next_hn++; /* XXX(hch): still racy */
shost->dma_channel = 0xff;

/* These three are default values which can be overridden */
@@ -259,6 +279,11 @@ struct Scsi_Host *scsi_host_alloc(struct
else
shost->dma_boundary = 0xffffffff;

+ host_no = alloc_host_no();
+ if (host_no < 0)
+ goto fail_kfree;
+ shost->host_no = host_no;
+
rval = scsi_setup_command_freelist(shost);
if (rval)
goto fail_kfree;
@@ -361,6 +386,7 @@ void scsi_host_put(struct Scsi_Host *sho

int scsi_init_hosts(void)
{
+ idr_init(&allocated_hosts);
return class_register(&shost_class);
}

_