bucket: copy key before Put

Application might change key value after seeking and before real put.
This unexpected behaviour could corrupt database. When users file issue,
maintainers doesn't know application behaviour. It could be caused by
data race. This patch is to prevent such case and save maintainers' time.

Signed-off-by: Wei Fu <fuweid89@gmail.com>
(cherry picked from commit a05ec68)
Signed-off-by: Wei Fu <fuweid89@gmail.com>

bucket.go

@@ -290,21 +290,22 @@ func (b *Bucket) Put(key []byte, value []byte) error {
 		return ErrValueTooLarge
 	}
 
+	// Insert into node.
+	// Tip: Use a new variable `newKey` instead of reusing the existing `key` to prevent
+	// it from being marked as leaking, and accordingly cannot be allocated on stack.
+	newKey := cloneBytes(key)
+
 	// Move cursor to correct position.
 	c := b.Cursor()
-	k, _, flags := c.seek(key)
+	k, _, flags := c.seek(newKey)
 
 	// Return an error if there is an existing key with a bucket value.
-	if bytes.Equal(key, k) && (flags&bucketLeafFlag) != 0 {
+	if bytes.Equal(newKey, k) && (flags&bucketLeafFlag) != 0 {
 		return ErrIncompatibleValue
 	}
 
 	// gofail: var beforeBucketPut struct{}
 
-	// Insert into node.
-	// Tip: Use a new variable `newKey` instead of reusing the existing `key` to prevent
-	// it from being marked as leaking, and accordingly cannot be allocated on stack.
-	newKey := cloneBytes(key)
 	c.node().put(newKey, newKey, value, 0, 0)
 
 	return nil