[PATCH 36/36] scsi: core: Protect host state changes with the host lock

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

Some but not all SCSI host state changes are protected with the SCSI
host lock. Annotate the SCSI host state with __guarded_by(&host_lock),
protect all SCSI host state changes with the SCSI host lock and use
READ_ONCE() for all SCSI host state reads. This patch prevents that
KCSAN complains about data races when accessing the SCSI host state.

Reported-by: Jianzhou Zhao <luckd0g@163.com>
Closes: https://lore.kernel.org/all/36d59d0e.6db0.19cdbeee01b.Coremail.luckd0g@163.com/
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/hosts.c                      | 13 ++++++++-----
 drivers/scsi/megaraid/megaraid_sas_base.c |  2 +-
 drivers/scsi/mpt3sas/mpt3sas_scsih.c      |  2 +-
 drivers/scsi/qla4xxx/ql4_os.c             |  6 ++----
 drivers/scsi/scsi_lib.c                   |  3 +--
 drivers/scsi/scsi_sysfs.c                 |  7 ++++---
 include/scsi/scsi_host.h                  | 23 ++++++++++++++++-------
 7 files changed, 33 insertions(+), 23 deletions(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index e047747d4ecf..7482ae7777c8 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -278,7 +278,8 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 	if (error)
 		goto out_disable_runtime_pm;
 
-	scsi_host_set_state(shost, SHOST_RUNNING);
+	scoped_guard(spinlock_irq, shost->host_lock)
+		scsi_host_set_state(shost, SHOST_RUNNING);
 	get_device(shost->shost_gendev.parent);
 
 	device_enable_async_suspend(&shost->shost_dev);
@@ -352,6 +353,7 @@ EXPORT_SYMBOL(scsi_add_host_with_dma);
 static void scsi_host_dev_release(struct device *dev)
 {
 	struct Scsi_Host *shost = dev_to_shost(dev);
+	enum scsi_host_state host_state = scsi_get_host_state(shost);
 	struct device *parent = dev->parent;
 
 	/* Wait for functions invoked through call_rcu(&scmd->rcu, ...) */
@@ -364,7 +366,7 @@ static void scsi_host_dev_release(struct device *dev)
 	if (shost->work_q)
 		destroy_workqueue(shost->work_q);
 
-	if (shost->shost_state == SHOST_CREATED) {
+	if (host_state == SHOST_CREATED) {
 		/*
 		 * Free the shost_dev device name and remove the proc host dir
 		 * here if scsi_host_{alloc,put}() have been called but neither
@@ -380,7 +382,7 @@ static void scsi_host_dev_release(struct device *dev)
 
 	ida_free(&host_index_ida, shost->host_no);
 
-	if (shost->shost_state != SHOST_CREATED)
+	if (host_state != SHOST_CREATED)
 		put_device(parent);
 	kfree(shost);
 }
@@ -414,7 +416,8 @@ struct Scsi_Host *scsi_host_alloc(const struct scsi_host_template *sht, int priv
 
 	shost->host_lock = &shost->default_lock;
 	spin_lock_init(shost->host_lock);
-	shost->shost_state = SHOST_CREATED;
+	scoped_guard(spinlock_init, shost->host_lock)
+		shost->shost_state = SHOST_CREATED;
 	INIT_LIST_HEAD(&shost->__devices);
 	INIT_LIST_HEAD(&shost->__targets);
 	INIT_LIST_HEAD(&shost->eh_abort_list);
@@ -600,7 +603,7 @@ EXPORT_SYMBOL(scsi_host_lookup);
  **/
 struct Scsi_Host *scsi_host_get(struct Scsi_Host *shost)
 {
-	if ((shost->shost_state == SHOST_DEL) ||
+	if (scsi_get_host_state(shost) == SHOST_DEL ||
 		!get_device(&shost->shost_gendev))
 		return NULL;
 	return shost;
diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c b/drivers/scsi/megaraid/megaraid_sas_base.c
index ccefe5841a17..97a81a86db82 100644
--- a/drivers/scsi/megaraid/megaraid_sas_base.c
+++ b/drivers/scsi/megaraid/megaraid_sas_base.c
@@ -3075,7 +3075,7 @@ static int megasas_reset_bus_host(struct scsi_cmnd *scmd)
 
 	scmd_printk(KERN_INFO, scmd,
 		"SCSI host state: %d  SCSI host busy: %d  FW outstanding: %d\n",
-		scmd->device->host->shost_state,
+		scsi_get_host_state(scmd->device->host),
 		scsi_host_busy(scmd->device->host),
 		atomic_read(&instance->fw_outstanding));
 	/*
diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
index 6ff788557294..e40913d2479e 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
@@ -5460,7 +5460,7 @@ static enum scsi_qc_status scsih_qcmd(struct Scsi_Host *shost,
 	 * Avoid error handling escallation when device is disconnected
 	 */
 	if (handle == MPT3SAS_INVALID_DEVICE_HANDLE || sas_device_priv_data->block) {
-		if (scmd->device->host->shost_state == SHOST_RECOVERY &&
+		if (scsi_get_host_state(scmd->device->host) == SHOST_RECOVERY &&
 		    scmd->cmnd[0] == TEST_UNIT_READY) {
 			scsi_build_sense(scmd, 0, UNIT_ATTENTION, 0x29, 0x07);
 			scsi_done(scmd);
diff --git a/drivers/scsi/qla4xxx/ql4_os.c b/drivers/scsi/qla4xxx/ql4_os.c
index d598ab4126f8..c9d9fc7c81fb 100644
--- a/drivers/scsi/qla4xxx/ql4_os.c
+++ b/drivers/scsi/qla4xxx/ql4_os.c
@@ -9411,11 +9411,9 @@ static int qla4xxx_eh_target_reset(struct scsi_cmnd *cmd)
  * This routine finds that if reset host is called in EH
  * scenario or from some application like sg_reset
  **/
-static int qla4xxx_is_eh_active(struct Scsi_Host *shost)
+static bool qla4xxx_is_eh_active(struct Scsi_Host *shost)
 {
-	if (shost->shost_state == SHOST_RECOVERY)
-		return 1;
-	return 0;
+	return scsi_get_host_state(shost) == SHOST_RECOVERY;
 }
 
 /**
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 6e8c7a42603e..5f7580b089e9 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1638,10 +1638,9 @@ static enum scsi_qc_status scsi_dispatch_cmd(struct scsi_cmnd *cmd)
 		goto done;
 	}
 
-	if (unlikely(host->shost_state == SHOST_DEL)) {
+	if (scsi_get_host_state(host) == SHOST_DEL) {
 		cmd->result = (DID_NO_CONNECT << 16);
 		goto done;
-
 	}
 
 	trace_scsi_dispatch_cmd_start(cmd);
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index dfc3559e7e04..9480432f650b 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -214,8 +214,9 @@ store_shost_state(struct device *dev, struct device_attribute *attr,
 	if (!state)
 		return -EINVAL;
 
-	if (scsi_host_set_state(shost, state))
-		return -EINVAL;
+	scoped_guard(spinlock_irq, shost->host_lock)
+		if (scsi_host_set_state(shost, state))
+			return -EINVAL;
 	return count;
 }
 
@@ -223,7 +224,7 @@ static ssize_t
 show_shost_state(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	struct Scsi_Host *shost = class_to_shost(dev);
-	const char *name = scsi_host_state_name(shost->shost_state);
+	const char *name = scsi_host_state_name(scsi_get_host_state(shost));
 
 	if (!name)
 		return -EINVAL;
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 2bbe7cb0060b..9841402e8bdf 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -729,7 +729,7 @@ struct Scsi_Host {
 	unsigned int  irq;
 	
 
-	enum scsi_host_state shost_state;
+	enum scsi_host_state shost_state __guarded_by(&host_lock);
 
 	/* ldm bits */
 	struct device		shost_gendev, shost_dev;
@@ -787,11 +787,18 @@ static inline struct Scsi_Host *dev_to_shost(struct device *dev)
 	return container_of(dev, struct Scsi_Host, shost_gendev);
 }
 
+static inline enum scsi_host_state scsi_get_host_state(struct Scsi_Host *shost)
+{
+	return context_unsafe(READ_ONCE(shost->shost_state));
+}
+
 static inline int scsi_host_in_recovery(struct Scsi_Host *shost)
 {
-	return shost->shost_state == SHOST_RECOVERY ||
-		shost->shost_state == SHOST_CANCEL_RECOVERY ||
-		shost->shost_state == SHOST_DEL_RECOVERY ||
+	enum scsi_host_state state = scsi_get_host_state(shost);
+
+	return state == SHOST_RECOVERY ||
+		state == SHOST_CANCEL_RECOVERY ||
+		state == SHOST_DEL_RECOVERY ||
 		shost->tmf_in_progress;
 }
 
@@ -837,8 +844,9 @@ static inline struct device *scsi_get_device(struct Scsi_Host *shost)
  **/
 static inline int scsi_host_scan_allowed(struct Scsi_Host *shost)
 {
-	return shost->shost_state == SHOST_RUNNING ||
-	       shost->shost_state == SHOST_RECOVERY;
+	enum scsi_host_state state = scsi_get_host_state(shost);
+
+	return state == SHOST_RUNNING || state == SHOST_RECOVERY;
 }
 
 extern void scsi_unblock_requests(struct Scsi_Host *);
@@ -942,6 +950,7 @@ static inline unsigned char scsi_host_get_guard(struct Scsi_Host *shost)
 	return shost->prot_guard_type;
 }
 
-extern int scsi_host_set_state(struct Scsi_Host *, enum scsi_host_state);
+int scsi_host_set_state(struct Scsi_Host *shost, enum scsi_host_state state)
+	__must_hold(&shost->host_lock);
 
 #endif /* _SCSI_SCSI_HOST_H */