[SCSI] sd: avoid deadlocks when running under multipath
When multipathed systems run into an all-paths-down scenario
all devices might be dropped, too. This causes 'del_gendisk'
to be called, which will unregister the kobj_map->probe()
function for all disk device numbers.
When the device comes back the default ->probe() function
is run which will call __request_module(), which will
deadlock.
As 'del_gendisk' typically does _not_ trigger a module unload
the default ->probe() function is pointless anyway.
This patch implements a dummy ->probe() function, which will
just return NULL if the disk is not registered.
This will avoid the deadlock. Plus it'll speed up device
scanning.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index c1c5552..a37eda9 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -504,6 +504,16 @@
};
/*
+ * Dummy kobj_map->probe function.
+ * The default ->probe function will call modprobe, which is
+ * pointless as this module is already loaded.
+ */
+static struct kobject *sd_default_probe(dev_t devt, int *partno, void *data)
+{
+ return NULL;
+}
+
+/*
* Device no to disk mapping:
*
* major disc2 disc p1
@@ -2970,8 +2980,10 @@
static int sd_remove(struct device *dev)
{
struct scsi_disk *sdkp;
+ dev_t devt;
sdkp = dev_get_drvdata(dev);
+ devt = disk_devt(sdkp->disk);
scsi_autopm_get_device(sdkp->device);
async_synchronize_full_domain(&scsi_sd_probe_domain);
@@ -2981,6 +2993,9 @@
del_gendisk(sdkp->disk);
sd_shutdown(dev);
+ blk_register_region(devt, SD_MINORS, NULL,
+ sd_default_probe, NULL, NULL);
+
mutex_lock(&sd_ref_mutex);
dev_set_drvdata(dev, NULL);
put_device(&sdkp->dev);
@@ -3124,9 +3139,13 @@
SCSI_LOG_HLQUEUE(3, printk("init_sd: sd driver entry point\n"));
- for (i = 0; i < SD_MAJORS; i++)
- if (register_blkdev(sd_major(i), "sd") == 0)
- majors++;
+ for (i = 0; i < SD_MAJORS; i++) {
+ if (register_blkdev(sd_major(i), "sd") != 0)
+ continue;
+ majors++;
+ blk_register_region(sd_major(i), SD_MINORS, NULL,
+ sd_default_probe, NULL, NULL);
+ }
if (!majors)
return -ENODEV;
@@ -3185,8 +3204,10 @@
class_unregister(&sd_disk_class);
- for (i = 0; i < SD_MAJORS; i++)
+ for (i = 0; i < SD_MAJORS; i++) {
+ blk_unregister_region(sd_major(i), SD_MINORS);
unregister_blkdev(sd_major(i), "sd");
+ }
}
module_init(init_sd);