smb3: mark compression as CONFIG_EXPERIMENTAL and fix missing compression operation

Move SMB3.1.1 compression code into experimental config option,
and fix the compress mount option. Implement unchained LZ77
"plain" compression algorithm as per MS-XCA specification
section "2.3 Plain LZ77 Compression Algorithm Details".

Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: smfrench

fs/smb/client/Kconfig

@@ -204,4 +204,18 @@ config CIFS_ROOT
 
 	  Most people say N here.
 
+config CIFS_COMPRESSION
+	bool "SMB message compression (Experimental)"
+	depends on CIFS
+	default n
+	help
+	  Enables over-the-wire message compression for SMB 3.1.1
+	  mounts when negotiated with the server.
+
+	  Only write requests with data size >= PAGE_SIZE will be
+	  compressed to avoid wasting resources.
+
+	  Say Y here if you want SMB traffic to be compressed.
+	  If unsure, say N.
+
 endif

fs/smb/client/Makefile

@@ -33,3 +33,5 @@ cifs-$(CONFIG_CIFS_SMB_DIRECT) += smbdirect.o
 cifs-$(CONFIG_CIFS_ROOT) += cifsroot.o
 
 cifs-$(CONFIG_CIFS_ALLOW_INSECURE_LEGACY) += smb1ops.o cifssmb.o
+
+cifs-$(CONFIG_CIFS_COMPRESSION) += compress.o compress/lz77.o

fs/smb/client/cifs_debug.c

@@ -349,6 +349,9 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 	seq_printf(m, ",ACL");
 #ifdef CONFIG_CIFS_SWN_UPCALL
 	seq_puts(m, ",WITNESS");
+#endif
+#ifdef CONFIG_CIFS_COMPRESSION
+	seq_puts(m, ",COMPRESSION");
 #endif
 	seq_putc(m, '\n');
 	seq_printf(m, "CIFSMaxBufSize: %d\n", CIFSMaxBufSize);
@@ -475,7 +478,9 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 		}
 
 		seq_puts(m, "\nCompression: ");
-		if (!server->compression.requested)
+		if (!IS_ENABLED(CONFIG_CIFS_COMPRESSION))
+			seq_puts(m, "no built-in support");
+		else if (!server->compression.requested)
 			seq_puts(m, "disabled on mount");
 		else if (server->compression.enabled)
 			seq_printf(m, "enabled (%s)", compression_alg_str(server->compression.alg));

fs/smb/client/cifsglob.h

@@ -555,7 +555,7 @@ struct smb_version_operations {
 	bool (*dir_needs_close)(struct cifsFileInfo *);
 	long (*fallocate)(struct file *, struct cifs_tcon *, int, loff_t,
 			  loff_t);
-	/* init transform request - used for encryption for now */
+	/* init transform (compress/encrypt) request */
 	int (*init_transform_rq)(struct TCP_Server_Info *, int num_rqst,
 				 struct smb_rqst *, struct smb_rqst *);
 	int (*is_transform_hdr)(void *buf);
@@ -1876,6 +1876,7 @@ static inline bool is_replayable_error(int error)
 #define   CIFS_HAS_CREDITS        0x0400 /* already has credits */
 #define   CIFS_TRANSFORM_REQ      0x0800 /* transform request before sending */
 #define   CIFS_NO_SRV_RSP         0x1000 /* there is no server response */
+#define   CIFS_COMPRESS_REQ       0x4000 /* compress request before sending */
 
 /* Security Flags: indicate type of session setup needed */
 #define   CIFSSEC_MAY_SIGN	0x00001

fs/smb/client/compress.c

@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024, SUSE LLC
+ *
+ * Authors: Enzo Matsumiya <ematsumiya@suse.de>
+ *
+ * This file implements I/O compression support for SMB2 messages (SMB 3.1.1 only).
+ * See compress/ for implementation details of each algorithm.
+ *
+ * References:
+ * MS-SMB2 "3.1.4.4 Compressing the Message"
+ * MS-SMB2 "3.1.5.3 Decompressing the Chained Message"
+ * MS-XCA - for details of the supported algorithms
+ */
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/uio.h>
+
+#include "cifsglob.h"
+#include "../common/smb2pdu.h"
+#include "cifsproto.h"
+#include "smb2proto.h"
+
+#include "compress/lz77.h"
+#include "compress.h"
+
+int smb_compress(void *buf, const void *data, size_t *len)
+{
+	struct smb2_compression_hdr *hdr;
+	size_t buf_len, data_len;
+	int ret;
+
+	buf_len = sizeof(struct smb2_write_req);
+	data_len = *len;
+	*len = 0;
+
+	hdr = buf;
+	hdr->ProtocolId = SMB2_COMPRESSION_TRANSFORM_ID;
+	hdr->OriginalCompressedSegmentSize = cpu_to_le32(data_len);
+	hdr->Offset = cpu_to_le32(buf_len);
+	hdr->Flags = SMB2_COMPRESSION_FLAG_NONE;
+	hdr->CompressionAlgorithm = SMB3_COMPRESS_LZ77;
+
+	/* XXX: add other algs here as they're implemented */
+	ret = lz77_compress(data, data_len, buf + SMB_COMPRESS_HDR_LEN + buf_len, &data_len);
+	if (!ret)
+		*len = SMB_COMPRESS_HDR_LEN + buf_len + data_len;
+
+	return ret;
+}

fs/smb/client/compress.h

@@ -0,0 +1,109 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024, SUSE LLC
+ *
+ * Authors: Enzo Matsumiya <ematsumiya@suse.de>
+ *
+ * This file implements I/O compression support for SMB2 messages (SMB 3.1.1 only).
+ * See compress/ for implementation details of each algorithm.
+ *
+ * References:
+ * MS-SMB2 "3.1.4.4 Compressing the Message" - for compression details
+ * MS-SMB2 "3.1.5.3 Decompressing the Chained Message" - for decompression details
+ * MS-XCA - for details of the supported algorithms
+ */
+#ifndef _SMB_COMPRESS_H
+#define _SMB_COMPRESS_H
+
+#include <linux/uio.h>
+#include <linux/kernel.h>
+#include "../common/smb2pdu.h"
+#include "cifsglob.h"
+
+/* sizeof(smb2_compression_hdr) - sizeof(OriginalPayloadSize) */
+#define SMB_COMPRESS_HDR_LEN		16
+/* sizeof(smb2_compression_payload_hdr) - sizeof(OriginalPayloadSize) */
+#define SMB_COMPRESS_PAYLOAD_HDR_LEN	8
+#define SMB_COMPRESS_MIN_LEN		PAGE_SIZE
+
+struct smb_compress_ctx {
+	struct TCP_Server_Info *server;
+	struct work_struct work;
+	struct mid_q_entry *mid;
+
+	void *buf; /* compressed data */
+	void *data; /* uncompressed data */
+	size_t len;
+};
+
+#ifdef CONFIG_CIFS_COMPRESSION
+int smb_compress(void *buf, const void *data, size_t *len);
+
+/**
+ * smb_compress_alg_valid() - Validate a compression algorithm.
+ * @alg: Compression algorithm to check.
+ * @valid_none: Conditional check whether NONE algorithm should be
+ *		considered valid or not.
+ *
+ * If @alg is SMB3_COMPRESS_NONE, this function returns @valid_none.
+ *
+ * Note that 'NONE' (0) compressor type is considered invalid in protocol
+ * negotiation, as it's never requested to/returned from the server.
+ *
+ * Return: true if @alg is valid/supported, false otherwise.
+ */
+static __always_inline int smb_compress_alg_valid(__le16 alg, bool valid_none)
+{
+	if (alg == SMB3_COMPRESS_NONE)
+		return valid_none;
+
+	if (alg == SMB3_COMPRESS_LZ77 || alg == SMB3_COMPRESS_PATTERN)
+		return true;
+
+	return false;
+}
+
+/**
+ * should_compress() - Determines if a request (write) or the response to a
+ *		       request (read) should be compressed.
+ * @tcon: tcon of the request is being sent to
+ * @buf: buffer with an SMB2 READ/WRITE request
+ *
+ * Return: true iff:
+ * - compression was successfully negotiated with server
+ * - server has enabled compression for the share
+ * - it's a read or write request
+ * - if write, request length is >= SMB_COMPRESS_MIN_LEN
+ *
+ * Return false otherwise.
+ */
+static __always_inline bool should_compress(const struct cifs_tcon *tcon, const void *buf)
+{
+	const struct smb2_hdr *shdr = buf;
+
+	if (!tcon || !tcon->ses || !tcon->ses->server)
+		return false;
+
+	if (!tcon->ses->server->compression.enabled)
+		return false;
+
+	if (!(tcon->share_flags & SMB2_SHAREFLAG_COMPRESS_DATA))
+		return false;
+
+	if (shdr->Command == SMB2_WRITE) {
+		const struct smb2_write_req *req = buf;
+
+		return (req->Length >= SMB_COMPRESS_MIN_LEN);
+	}
+
+	return (shdr->Command == SMB2_READ);
+}
+/*
+ * #else !CONFIG_CIFS_COMPRESSION ...
+ * These routines should not be called when CONFIG_CIFS_COMPRESSION disabled
+ * #define smb_compress(arg1, arg2, arg3)		(-EOPNOTSUPP)
+ * #define smb_compress_alg_valid(arg1, arg2)	(-EOPNOTSUPP)
+ * #define should_compress(arg1, arg2)		(false)
+ */
+#endif /* !CONFIG_CIFS_COMPRESSION */
+#endif /* _SMB_COMPRESS_H */