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Commit 0761df9c authored by Hannes Reinecke's avatar Hannes Reinecke Committed by James Bottomley
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[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: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent 70288b4c

drivers/scsi/sd.c

+25 −4
Original line number Original line Diff line number Diff line
@@ -503,6 +503,16 @@ static struct scsi_driver sd_template = { 
	.eh_action		= sd_eh_action,

	.eh_action		= sd_eh_action,

};

};





/*

 * 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:

 * Device no to disk mapping:

 * 

 *
@@ -2970,8 +2980,10 @@ static int sd_probe(struct device *dev) 
static int sd_remove(struct device *dev)

static int sd_remove(struct device *dev)

{

{

	struct scsi_disk *sdkp;

	struct scsi_disk *sdkp;

	dev_t devt;





	sdkp = dev_get_drvdata(dev);

	sdkp = dev_get_drvdata(dev);

	devt = disk_devt(sdkp->disk);

	scsi_autopm_get_device(sdkp->device);

	scsi_autopm_get_device(sdkp->device);





	async_synchronize_full_domain(&scsi_sd_probe_domain);

	async_synchronize_full_domain(&scsi_sd_probe_domain);
@@ -2981,6 +2993,9 @@ static int sd_remove(struct device *dev) 
	del_gendisk(sdkp->disk);

	del_gendisk(sdkp->disk);

	sd_shutdown(dev);

	sd_shutdown(dev);





	blk_register_region(devt, SD_MINORS, NULL,

			    sd_default_probe, NULL, NULL);



	mutex_lock(&sd_ref_mutex);

	mutex_lock(&sd_ref_mutex);

	dev_set_drvdata(dev, NULL);

	dev_set_drvdata(dev, NULL);

	put_device(&sdkp->dev);

	put_device(&sdkp->dev);
@@ -3124,9 +3139,13 @@ static int __init init_sd(void) 




	SCSI_LOG_HLQUEUE(3, printk("init_sd: sd driver entry point\n"));

	SCSI_LOG_HLQUEUE(3, printk("init_sd: sd driver entry point\n"));





	for (i = 0; i < SD_MAJORS; i++)

	for (i = 0; i < SD_MAJORS; i++) {

		if (register_blkdev(sd_major(i), "sd") == 0)

		if (register_blkdev(sd_major(i), "sd") != 0)

			continue;

		majors++;

		majors++;

		blk_register_region(sd_major(i), SD_MINORS, NULL,

				    sd_default_probe, NULL, NULL);

	}





	if (!majors)

	if (!majors)

		return -ENODEV;

		return -ENODEV;
@@ -3185,9 +3204,11 @@ static void __exit exit_sd(void) 




	class_unregister(&sd_disk_class);

	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");

		unregister_blkdev(sd_major(i), "sd");

	}

	}

}





module_init(init_sd);

module_init(init_sd);

module_exit(exit_sd);

module_exit(exit_sd);