memstick: avert possible race condition between idr_pre_get and idr_g…

…et_new Implement the usual pattern around idr_pre_get() and idr_get_new() to handlethe situation where another thread concurrently steals this thread's idr_pre_get() preallocation. Signed-off-by: Alex Dubov <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
chewitt · Jan 13, 2011 · d8256d4 · d8256d4
1 parent 8930c8a
commit d8256d4
Show file tree

Hide file tree

Showing 2 changed files with 15 additions and 9 deletions.
diff --git a/drivers/memstick/core/memstick.c b/drivers/memstick/core/memstick.c
@@ -511,14 +511,18 @@ int memstick_add_host(struct memstick_host *host)
 {
 	int rc;
 
-	if (!idr_pre_get(&memstick_host_idr, GFP_KERNEL))
-		return -ENOMEM;
+	while (1) {
+		if (!idr_pre_get(&memstick_host_idr, GFP_KERNEL))
+			return -ENOMEM;
 
-	spin_lock(&memstick_host_lock);
-	rc = idr_get_new(&memstick_host_idr, host, &host->id);
-	spin_unlock(&memstick_host_lock);
-	if (rc)
-		return rc;
+		spin_lock(&memstick_host_lock);
+		rc = idr_get_new(&memstick_host_idr, host, &host->id);
+		spin_unlock(&memstick_host_lock);
+		if (!rc)
+			break;
+		else if (rc != -EAGAIN)
+			return rc;
+	}
 
 	dev_set_name(&host->dev, "memstick%u", host->id);
 

diff --git a/drivers/memstick/core/mspro_block.c b/drivers/memstick/core/mspro_block.c
@@ -1206,10 +1206,12 @@ static int mspro_block_init_disk(struct memstick_dev *card)
 
 	msb->page_size = be16_to_cpu(sys_info->unit_size);
 
-	if (!idr_pre_get(&mspro_block_disk_idr, GFP_KERNEL))
+	mutex_lock(&mspro_block_disk_lock);
+	if (!idr_pre_get(&mspro_block_disk_idr, GFP_KERNEL)) {
+		mutex_unlock(&mspro_block_disk_lock);
 		return -ENOMEM;
+	}
 
-	mutex_lock(&mspro_block_disk_lock);
 	rc = idr_get_new(&mspro_block_disk_idr, card, &disk_id);
 	mutex_unlock(&mspro_block_disk_lock);