[PATCH 08/18] sd: use __register_blkdev to avoid a modprobe for an unregistered dev_t

From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Denis Efremov <efremov@linux.com>,
	"David S. Miller" <davem@davemloft.net>,
	Song Liu <song@kernel.org>, Al Viro <viro@zeniv.linux.org.uk>,
	Finn Thain <fthain@telegraphics.com.au>,
	Michael Schmitz <schmitzmic@gmail.com>,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-ide@vger.kernel.org, linux-raid@vger.kernel.org,
	linux-scsi@vger.kernel.org, linux-m68k@lists.linux-m68k.org,
	Hannes Reinecke <hare@suse.de>
Subject: [PATCH 08/18] sd: use __register_blkdev to avoid a modprobe for an unregistered dev_t
Date: Thu, 29 Oct 2020 15:58:31 +0100	[thread overview]
Message-ID: <20201029145841.144173-9-hch@lst.de> (raw)
In-Reply-To: <20201029145841.144173-1-hch@lst.de>

Switch from using blk_register_region to the probe callback passed to
__register_blkdev to disable the request_module call for an unclaimed
dev_t in the SD majors.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/sd.c | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 656bcf4940d6d1..106a9cda0eb7ed 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -630,13 +630,11 @@ 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.
+ * Don't request a new module, as that could deadlock in multipath
+ * environment.
  */
-static struct kobject *sd_default_probe(dev_t devt, int *partno, void *data)
+static void sd_default_probe(dev_t devt)
 {
-	return NULL;
 }
 
 /*
@@ -3528,9 +3526,6 @@ static int sd_remove(struct device *dev)
 
 	free_opal_dev(sdkp->opal_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);
@@ -3720,11 +3715,9 @@ 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)
+		if (__register_blkdev(sd_major(i), "sd", sd_default_probe))
 			continue;
 		majors++;
-		blk_register_region(sd_major(i), SD_MINORS, NULL,
-				    sd_default_probe, NULL, NULL);
 	}
 
 	if (!majors)
@@ -3797,10 +3790,8 @@ static void __exit exit_sd(void)
 
 	class_unregister(&sd_disk_class);
 
-	for (i = 0; i < SD_MAJORS; i++) {
-		blk_unregister_region(sd_major(i), SD_MINORS);
+	for (i = 0; i < SD_MAJORS; i++)
 		unregister_blkdev(sd_major(i), "sd");
-	}
 }
 
 module_init(init_sd);
-- 
2.28.0

