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 <[email protected]> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index 7992635..2ee0aa6 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -489,6 +489,16 @@ static struct scsi_driver sd_template = { }; /* + * 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 @@ -2961,8 +2971,10 @@ static int sd_probe(struct device *dev) 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); @@ -2972,6 +2984,9 @@ static int sd_remove(struct device *dev) 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); @@ -3115,9 +3130,13 @@ static int __init init_sd(void) 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; @@ -3176,8 +3195,10 @@ static void __exit exit_sd(void) 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); -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
