1 files changed, 26 insertions, 19 deletions

diff --git a/fs/smb/common/smb2pdu.h b/fs/smb/common/smb2pdu.h
index 17f1bddb95d0..20784f76a604 100644
--- a/fs/smb/common/smb2pdu.h
+++ b/fs/smb/common/smb2pdu.h
@@ -208,36 +208,43 @@ struct smb2_transform_hdr {
 	__le64  SessionId;
 } __packed;
 
+/*
+ * These are simplified versions from the spec, as we don't need a fully fledged
+ * form of both unchained and chained structs.
+ *
+ * Moreover, even in chained compressed payloads, the initial compression header
+ * has the form of the unchained one -- i.e. it never has the
+ * OriginalPayloadSize field and ::Offset field always represent an offset
+ * (instead of a length, as it is in the chained header).
+ *
+ * See MS-SMB2 2.2.42 for more details.
+ */
+#define SMB2_COMPRESSION_FLAG_NONE	0x0000
+#define SMB2_COMPRESSION_FLAG_CHAINED	0x0001
 
-/* See MS-SMB2 2.2.42 */
-struct smb2_compression_transform_hdr_unchained {
-	__le32 ProtocolId;	/* 0xFC 'S' 'M' 'B' */
+struct smb2_compression_hdr {
+	__le32 ProtocolId; /* 0xFC 'S' 'M' 'B' */
 	__le32 OriginalCompressedSegmentSize;
 	__le16 CompressionAlgorithm;
 	__le16 Flags;
-	__le16 Length; /* if chained it is length, else offset */
+	__le16 Offset; /* this is the size of the uncompressed SMB2 header below */
+	/* uncompressed SMB2 header (READ or WRITE) goes here */
+	/* compressed data goes here */
 } __packed;
 
-/* See MS-SMB2 2.2.42.1 */
-#define SMB2_COMPRESSION_FLAG_NONE	0x0000
-#define SMB2_COMPRESSION_FLAG_CHAINED	0x0001
-
-struct compression_payload_header {
+/*
+ * ... OTOH, set compression payload header to always have OriginalPayloadSize
+ * as it's easier to pass the struct size minus sizeof(OriginalPayloadSize)
+ * than to juggle around the header/data memory.
+ */
+struct smb2_compression_payload_hdr {
 	__le16	CompressionAlgorithm;
 	__le16	Flags;
 	__le32	Length; /* length of compressed playload including field below if present */
-	/* __le32 OriginalPayloadSize; */ /* optional, present when LZNT1, LZ77, LZ77+Huffman */
-} __packed;
-
-/* See MS-SMB2 2.2.42.2 */
-struct smb2_compression_transform_hdr_chained {
-	__le32 ProtocolId;	/* 0xFC 'S' 'M' 'B' */
-	__le32 OriginalCompressedSegmentSize;
-	/* struct compression_payload_header[] */
+	__le32 OriginalPayloadSize; /* accounted when LZNT1, LZ77, LZ77+Huffman */
 } __packed;
 
-/* See MS-SMB2 2.2.42.2.2 */
-struct compression_pattern_payload_v1 {
+struct smb2_compression_pattern_v1 {
 	__u8	Pattern;
 	__u8	Reserved1;
 	__le16	Reserved2;