[PATCH v7 8/8] scsi: core: Release SCSI devices synchronously

[Bart Van Assche <bvanassche@acm.org>]

All upstream scsi_device_put() calls happen from thread context. Hence
simplify scsi_device_put() by always calling the release function
synchronously. This patch prepares for constifying the SCSI host template
by removing an assignment that clears the module pointer in the SCSI host
template.

scsi_device_dev_release_usercontext() was introduced in 2006 via
commit 65110b216895 ("[SCSI] fix wrong context bugs in SCSI").

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: John Garry <john.garry@huawei.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi.c        |  2 ++
 drivers/scsi/scsi_sysfs.c  | 22 ++--------------------
 include/scsi/scsi_device.h |  1 -
 3 files changed, 4 insertions(+), 21 deletions(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 9feb0323bc44..1426b9b03612 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -588,6 +588,8 @@ void scsi_device_put(struct scsi_device *sdev)
 {
 	struct module *mod = sdev->host->hostt->module;
 
+	might_sleep();
+
 	put_device(&sdev->sdev_gendev);
 	module_put(mod);
 }
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index c8b178983585..c76f5757b863 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -441,20 +441,15 @@ static void scsi_device_cls_release(struct device *class_dev)
 	put_device(&sdev->sdev_gendev);
 }
 
-static void scsi_device_dev_release_usercontext(struct work_struct *work)
+static void scsi_device_dev_release(struct device *dev)
 {
-	struct scsi_device *sdev;
+	struct scsi_device *sdev = to_scsi_device(dev);
 	struct device *parent;
 	struct list_head *this, *tmp;
 	struct scsi_vpd *vpd_pg80 = NULL, *vpd_pg83 = NULL;
 	struct scsi_vpd *vpd_pg0 = NULL, *vpd_pg89 = NULL;
 	struct scsi_vpd *vpd_pgb0 = NULL, *vpd_pgb1 = NULL, *vpd_pgb2 = NULL;
 	unsigned long flags;
-	struct module *mod;
-
-	sdev = container_of(work, struct scsi_device, ew.work);
-
-	mod = sdev->host->hostt->module;
 
 	parent = sdev->sdev_gendev.parent;
 
@@ -516,19 +511,6 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
 
 	if (parent)
 		put_device(parent);
-	module_put(mod);
-}
-
-static void scsi_device_dev_release(struct device *dev)
-{
-	struct scsi_device *sdp = to_scsi_device(dev);
-
-	/* Set module pointer as NULL in case of module unloading */
-	if (!try_module_get(sdp->host->hostt->module))
-		sdp->host->hostt->module = NULL;
-
-	execute_in_process_context(scsi_device_dev_release_usercontext,
-				   &sdp->ew);
 }
 
 static struct class sdev_class = {
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index c36656d8ac6c..24bdbf7999ab 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -236,7 +236,6 @@ struct scsi_device {
 	struct device		sdev_gendev,
 				sdev_dev;
 
-	struct execute_work	ew; /* used to get process context on put */
 	struct work_struct	requeue_work;
 
 	struct scsi_device_handler *handler;