ubifs: Add support for zstd compression.

zstd shows a good compression rate and is faster than lzo,
also on slow ARM cores.

Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Signed-off-by: Michele Dionisio <michele.dionisio@gmail.com>
[rw: rewrote commit message]
Signed-off-by: Richard Weinberger <richard@nod.at>

fs/ubifs/Kconfig

@@ -6,8 +6,10 @@ config UBIFS_FS
 	select CRYPTO if UBIFS_FS_ADVANCED_COMPR
 	select CRYPTO if UBIFS_FS_LZO
 	select CRYPTO if UBIFS_FS_ZLIB
+	select CRYPTO if UBIFS_FS_ZSTD
 	select CRYPTO_LZO if UBIFS_FS_LZO
 	select CRYPTO_DEFLATE if UBIFS_FS_ZLIB
+	select CRYPTO_ZSTD if UBIFS_FS_ZSTD
 	select CRYPTO_HASH_INFO
 	select UBIFS_FS_XATTR if FS_ENCRYPTION
 	depends on MTD_UBI
@@ -38,6 +40,14 @@ config UBIFS_FS_ZLIB
 	help
 	  Zlib compresses better than LZO but it is slower. Say 'Y' if unsure.
 
+config UBIFS_FS_ZSTD
+	bool "ZSTD compression support" if UBIFS_FS_ADVANCED_COMPR
+	depends on UBIFS_FS
+	default y
+	help
+	  ZSTD compresses is a big win in speed over Zlib and
+	  in compression ratio over LZO. Say 'Y' if unsure.
+
 config UBIFS_ATIME_SUPPORT
 	bool "Access time support"
 	default n

fs/ubifs/compress.c

@@ -59,6 +59,24 @@ static struct ubifs_compressor zlib_compr = {
 };
 #endif
 
+#ifdef CONFIG_UBIFS_FS_ZSTD
+static DEFINE_MUTEX(zstd_enc_mutex);
+static DEFINE_MUTEX(zstd_dec_mutex);
+
+static struct ubifs_compressor zstd_compr = {
+	.compr_type = UBIFS_COMPR_ZSTD,
+	.comp_mutex = &zstd_enc_mutex,
+	.decomp_mutex = &zstd_dec_mutex,
+	.name = "zstd",
+	.capi_name = "zstd",
+};
+#else
+static struct ubifs_compressor zstd_compr = {
+	.compr_type = UBIFS_COMPR_ZSTD,
+	.name = "zstd",
+};
+#endif
+
 /* All UBIFS compressors */
 struct ubifs_compressor *ubifs_compressors[UBIFS_COMPR_TYPES_CNT];
 
@@ -216,13 +234,19 @@ int __init ubifs_compressors_init(void)
 	if (err)
 		return err;
 
-	err = compr_init(&zlib_compr);
+	err = compr_init(&zstd_compr);
 	if (err)
 		goto out_lzo;
 
+	err = compr_init(&zlib_compr);
+	if (err)
+		goto out_zstd;
+
 	ubifs_compressors[UBIFS_COMPR_NONE] = &none_compr;
 	return 0;
 
+out_zstd:
+	compr_exit(&zstd_compr);
 out_lzo:
 	compr_exit(&lzo_compr);
 	return err;
@@ -235,4 +259,5 @@ void ubifs_compressors_exit(void)
 {
 	compr_exit(&lzo_compr);
 	compr_exit(&zlib_compr);
+	compr_exit(&zstd_compr);
 }

fs/ubifs/super.c

@@ -1045,6 +1045,8 @@ static int ubifs_parse_options(struct ubifs_info *c, char *options,
 				c->mount_opts.compr_type = UBIFS_COMPR_LZO;
 			else if (!strcmp(name, "zlib"))
 				c->mount_opts.compr_type = UBIFS_COMPR_ZLIB;
+			else if (!strcmp(name, "zstd"))
+				c->mount_opts.compr_type = UBIFS_COMPR_ZSTD;
 			else {
 				ubifs_err(c, "unknown compressor \"%s\"", name); //FIXME: is c ready?
 				kfree(name);

fs/ubifs/ubifs-media.h

@@ -340,12 +340,14 @@ enum {
  * UBIFS_COMPR_NONE: no compression
  * UBIFS_COMPR_LZO: LZO compression
  * UBIFS_COMPR_ZLIB: ZLIB compression
+ * UBIFS_COMPR_ZSTD: ZSTD compression
  * UBIFS_COMPR_TYPES_CNT: count of supported compression types
  */
 enum {
 	UBIFS_COMPR_NONE,
 	UBIFS_COMPR_LZO,
 	UBIFS_COMPR_ZLIB,
+	UBIFS_COMPR_ZSTD,
 	UBIFS_COMPR_TYPES_CNT,
 };