[PATCH] scsi: core: Fix missing lock when read async_scan in Scsi_Host

[Chaohai Chen]

When setting the async_scan flag in host, the host lock was locked,
but it is not locked during reading. Encapsulate the corresponding
API to fix this issue.

Signed-off-by: Chaohai Chen <wdhh6@xxxxxxxxxx>
---
 drivers/scsi/scsi_scan.c | 60 +++++++++++++++++++++++++++++-----------
 1 file changed, 44 insertions(+), 16 deletions(-)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 60c06fa4ec32..8b63130ef2e5 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -122,6 +122,42 @@ struct async_scan_data {
 	struct completion prev_finished;
 };
 
+static bool scsi_test_async_scan(struct Scsi_Host *shost)
+{
+	bool async;
+	unsigned long flags;
+
+	lockdep_assert_not_held(shost->host_lock);
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	async = shost->async_scan;
+	spin_unlock_irqrestore(shost->host_lock, flags);
+
+	return async;
+}
+
+static void scsi_set_async_scan(struct Scsi_Host *shost)
+{
+	unsigned long flags;
+
+	lockdep_assert_not_held(shost->host_lock);
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	shost->async_scan = 1;
+	spin_unlock_irqrestore(shost->host_lock, flags);
+}
+
+static void scsi_clear_async_scan(struct Scsi_Host *shost)
+{
+	unsigned long flags;
+
+	lockdep_assert_not_held(shost->host_lock);
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	shost->async_scan = 0;
+	spin_unlock_irqrestore(shost->host_lock, flags);
+}
+
 /*
  * scsi_enable_async_suspend - Enable async suspend and resume
  */
@@ -1298,7 +1334,7 @@ static int scsi_probe_and_add_lun(struct scsi_target *starget,
 		goto out_free_result;
 	}
 
-	res = scsi_add_lun(sdev, result, &bflags, shost->async_scan);
+	res = scsi_add_lun(sdev, result, &bflags, scsi_test_async_scan(shost));
 	if (res == SCSI_SCAN_LUN_PRESENT) {
 		if (bflags & BLIST_KEY) {
 			sdev->lockable = 0;
@@ -1629,7 +1665,7 @@ struct scsi_device *__scsi_add_device(struct Scsi_Host *shost, uint channel,
 	scsi_autopm_get_target(starget);
 
 	mutex_lock(&shost->scan_mutex);
-	if (!shost->async_scan)
+	if (!scsi_test_async_scan(shost))
 		scsi_complete_async_scans();
 
 	if (scsi_host_scan_allowed(shost) && scsi_autopm_get_host(shost) == 0) {
@@ -1839,7 +1875,7 @@ void scsi_scan_target(struct device *parent, unsigned int channel,
 		return;
 
 	mutex_lock(&shost->scan_mutex);
-	if (!shost->async_scan)
+	if (!scsi_test_async_scan(shost))
 		scsi_complete_async_scans();
 
 	if (scsi_host_scan_allowed(shost) && scsi_autopm_get_host(shost) == 0) {
@@ -1896,7 +1932,7 @@ int scsi_scan_host_selected(struct Scsi_Host *shost, unsigned int channel,
 		return -EINVAL;
 
 	mutex_lock(&shost->scan_mutex);
-	if (!shost->async_scan)
+	if (!scsi_test_async_scan(shost))
 		scsi_complete_async_scans();
 
 	if (scsi_host_scan_allowed(shost) && scsi_autopm_get_host(shost) == 0) {
@@ -1943,13 +1979,12 @@ static void scsi_sysfs_add_devices(struct Scsi_Host *shost)
 static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
 {
 	struct async_scan_data *data = NULL;
-	unsigned long flags;
 
 	if (strncmp(scsi_scan_type, "sync", 4) == 0)
 		return NULL;
 
 	mutex_lock(&shost->scan_mutex);
-	if (shost->async_scan) {
+	if (scsi_test_async_scan(shost)) {
 		shost_printk(KERN_DEBUG, shost, "%s called twice\n", __func__);
 		goto err;
 	}
@@ -1961,10 +1996,7 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
 	if (!data->shost)
 		goto err;
 	init_completion(&data->prev_finished);
-
-	spin_lock_irqsave(shost->host_lock, flags);
-	shost->async_scan = 1;
-	spin_unlock_irqrestore(shost->host_lock, flags);
+	scsi_set_async_scan(shost);
 	mutex_unlock(&shost->scan_mutex);
 
 	spin_lock(&async_scan_lock);
@@ -1992,7 +2024,6 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
 static void scsi_finish_async_scan(struct async_scan_data *data)
 {
 	struct Scsi_Host *shost;
-	unsigned long flags;
 
 	if (!data)
 		return;
@@ -2001,7 +2032,7 @@ static void scsi_finish_async_scan(struct async_scan_data *data)
 
 	mutex_lock(&shost->scan_mutex);
 
-	if (!shost->async_scan) {
+	if (!scsi_test_async_scan(shost)) {
 		shost_printk(KERN_INFO, shost, "%s called twice\n", __func__);
 		dump_stack();
 		mutex_unlock(&shost->scan_mutex);
@@ -2011,10 +2042,7 @@ static void scsi_finish_async_scan(struct async_scan_data *data)
 	wait_for_completion(&data->prev_finished);
 
 	scsi_sysfs_add_devices(shost);
-
-	spin_lock_irqsave(shost->host_lock, flags);
-	shost->async_scan = 0;
-	spin_unlock_irqrestore(shost->host_lock, flags);
+	scsi_clear_async_scan(shost);
 
 	mutex_unlock(&shost->scan_mutex);
 
-- 
2.43.7