[RFC PATCH] jffs2: add support for zstd compression

Rui Salvaterra
2021-03-12T09:57:48Z

Implement support for zstd compression in jffs2 at the default compression
level (3).

Lightly tested in OpenWrt, on a single CPU embedded MIPS32 system (AirGrid M2).

Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>
---
Sent as RFC, since I have no idea if locking is required (the crypto API
implementation doesn't do it, at least).

fs/jffs2/Kconfig | 9 +++
fs/jffs2/Makefile | 1 +
fs/jffs2/compr.c | 10 +++
fs/jffs2/compr.h | 6 ++
fs/jffs2/compr_zstd.c | 131 +++++++++++++++++++++++++++++++++++++
fs/jffs2/super.c | 7 ++
include/uapi/linux/jffs2.h | 1 +
7 files changed, 165 insertions(+)
create mode 100644 fs/jffs2/compr_zstd.c

diff --git a/fs/jffs2/Kconfig b/fs/jffs2/Kconfig
index 7c96bc107218..31308eb7267b 100644
--- a/fs/jffs2/Kconfig
+++ b/fs/jffs2/Kconfig
@@ -136,6 +136,15 @@ config JFFS2_LZO
This feature was added in July, 2007. Say 'N' if you need
compatibility with older bootloaders or kernels.

+config JFFS2_ZSTD
+ bool "JFFS2 zstd compression support" if JFFS2_COMPRESSION_OPTIONS
+ select ZSTD_COMPRESS
+ select ZSTD_DECOMPRESS
+ depends on JFFS2_FS
+ default n
+ help
+ Zstd compression.
+
config JFFS2_RTIME
bool "JFFS2 RTIME compression support" if JFFS2_COMPRESSION_OPTIONS
depends on JFFS2_FS
diff --git a/fs/jffs2/Makefile b/fs/jffs2/Makefile
index 5294969d5bf9..75f84b1467c5 100644
--- a/fs/jffs2/Makefile
+++ b/fs/jffs2/Makefile
@@ -19,4 +19,5 @@ jffs2-$(CONFIG_JFFS2_RUBIN) += compr_rubin.o
jffs2-$(CONFIG_JFFS2_RTIME) += compr_rtime.o
jffs2-$(CONFIG_JFFS2_ZLIB) += compr_zlib.o
jffs2-$(CONFIG_JFFS2_LZO) += compr_lzo.o
+jffs2-$(CONFIG_JFFS2_ZSTD) += compr_zstd.o
jffs2-$(CONFIG_JFFS2_SUMMARY) += summary.o
diff --git a/fs/jffs2/compr.c b/fs/jffs2/compr.c
index 4849a4c9a0e2..d65e0c39c9c5 100644
--- a/fs/jffs2/compr.c
+++ b/fs/jffs2/compr.c
@@ -237,6 +237,10 @@ uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
ret = jffs2_selected_compress(JFFS2_COMPR_ZLIB, data_in,
cpage_out, datalen, cdatalen);
break;
+ case JFFS2_COMPR_MODE_FORCEZSTD:
+ ret = jffs2_selected_compress(JFFS2_COMPR_ZSTD, data_in,
+ cpage_out, datalen, cdatalen);
+ break;
default:
pr_err("unknown compression mode\n");
}
@@ -378,6 +382,9 @@ int __init jffs2_compressors_init(void)
#ifdef CONFIG_JFFS2_LZO
jffs2_lzo_init();
#endif
+#ifdef CONFIG_JFFS2_ZSTD
+ jffs2_zstd_init();
+#endif
/* Setting default compression mode */
#ifdef CONFIG_JFFS2_CMODE_NONE
jffs2_compression_mode = JFFS2_COMPR_MODE_NONE;
@@ -413,6 +420,9 @@ int jffs2_compressors_exit(void)
#endif
#ifdef CONFIG_JFFS2_ZLIB
jffs2_zlib_exit();
+#endif
+#ifdef CONFIG_JFFS2_ZSTD
+ jffs2_zstd_exit();
#endif
return 0;
}
diff --git a/fs/jffs2/compr.h b/fs/jffs2/compr.h
index 5e91d578f4ed..8f7032c5ecb2 100644
--- a/fs/jffs2/compr.h
+++ b/fs/jffs2/compr.h
@@ -31,6 +31,7 @@
#define JFFS2_RTIME_PRIORITY 50
#define JFFS2_ZLIB_PRIORITY 60
#define JFFS2_LZO_PRIORITY 80
+#define JFFS2_ZSTD_PRIORITY 90

#define JFFS2_RUBINMIPS_DISABLED /* RUBINs will be used only */
@@ -42,6 +43,7 @@
#define JFFS2_COMPR_MODE_FAVOURLZO 3
#define JFFS2_COMPR_MODE_FORCELZO 4
#define JFFS2_COMPR_MODE_FORCEZLIB 5
+#define JFFS2_COMPR_MODE_FORCEZSTD 6

#define FAVOUR_LZO_PERCENT 80

@@ -101,5 +103,9 @@ void jffs2_zlib_exit(void);
int jffs2_lzo_init(void);
void jffs2_lzo_exit(void);
#endif
+#ifdef CONFIG_JFFS2_ZSTD
+int jffs2_zstd_init(void);
+void jffs2_zstd_exit(void);
+#endif

#endif /* __JFFS2_COMPR_H__ */
diff --git a/fs/jffs2/compr_zstd.c b/fs/jffs2/compr_zstd.c
new file mode 100644
index 000000000000..86b3d28670d7
--- /dev/null
+++ b/fs/jffs2/compr_zstd.c
@@ -0,0 +1,131 @@
+
+#include <linux/zstd.h>
+#include "compr.h"
+
+#define ZSTD_DEF_LEVEL 3
+
+static ZSTD_CCtx *cctx;
+static ZSTD_DCtx *dctx;
+static void *cwksp;
+static void *dwksp;
+
+static ZSTD_parameters zstd_params(void)
+{
+ return ZSTD_getParams(ZSTD_DEF_LEVEL, 0, 0);
+}
+
+static int zstd_comp_init(void)
+{
+ int ret = 0;
+ const ZSTD_parameters params = zstd_params();
+ const size_t wksp_size = ZSTD_CCtxWorkspaceBound(params.cParams);
+
+ cwksp = vzalloc(wksp_size);
+ if (!cwksp) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ cctx = ZSTD_initCCtx(cwksp, wksp_size);
+ if (cctx) {
+ ret = -EINVAL;
+ goto out_free;
+ }
+out:
+ return ret;
+out_free:
+ vfree(cwksp);
+ goto out;
+}
+
+static int zstd_decomp_init(void)
+{
+ int ret = 0;
+ const size_t wksp_size = ZSTD_DCtxWorkspaceBound();
+
+ dwksp = vzalloc(wksp_size);
+ if (!dwksp) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ dctx = ZSTD_initDCtx(dwksp, wksp_size);
+ if (!dctx) {
+ ret = -EINVAL;
+ goto out_free;
+ }
+out:
+ return ret;
+out_free:
+ vfree(dwksp);
+ goto out;
+}
+
+static void zstd_comp_exit(void)
+{
+ vfree(cwksp);
+ cwksp = NULL;
+ cctx = NULL;
+}
+
+static void zstd_decomp_exit(void)
+{
+ vfree(dwksp);
+ dwksp = NULL;
+ dctx = NULL;
+}
+
+static int jffs2_zstd_compress(unsigned char *data_in, unsigned char *cpage_out,
+ uint32_t *sourcelen, uint32_t *dstlen)
+{
+ size_t out_len;
+ const ZSTD_parameters params = zstd_params();
+
+ out_len = ZSTD_compressCCtx(cctx, cpage_out, *dstlen, data_in, *sourcelen, params);
+ if (ZSTD_isError(out_len) || out_len > *dstlen)
+ return -1;
+ *dstlen = out_len;
+ return 0;
+}
+
+static int jffs2_zstd_decompress(unsigned char *data_in, unsigned char *cpage_out,
+ uint32_t srclen, uint32_t destlen)
+{
+ size_t out_len;
+
+ out_len = ZSTD_decompressDCtx(dctx, cpage_out, destlen, data_in, srclen);
+ if (ZSTD_isError(out_len) || out_len != destlen)
+ return -1;
+
+ return 0;
+}
+
+static struct jffs2_compressor jffs2_zstd_comp = {
+ .priority = JFFS2_ZSTD_PRIORITY,
+ .name = "zstd",
+ .compr = JFFS2_COMPR_ZSTD,
+ .compress = &jffs2_zstd_compress,
+ .decompress = &jffs2_zstd_decompress,
+ .disabled = 0,
+};
+
+int __init jffs2_zstd_init(void)
+{
+ int ret;
+
+ ret = zstd_comp_init();
+ if (ret)
+ return ret;
+ ret = zstd_decomp_init();
+ if (ret)
+ zstd_comp_exit();
+ ret = jffs2_register_compressor(&jffs2_zstd_comp);
+ return ret;
+}
+
+void jffs2_zstd_exit(void)
+{
+ jffs2_unregister_compressor(&jffs2_zstd_comp);
+ zstd_comp_exit();
+ zstd_decomp_exit();
+}
diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c
index 81ca58c10b72..ddce95c55dde 100644
--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -73,6 +73,10 @@ static const char *jffs2_compr_name(unsigned int compr)
#ifdef CONFIG_JFFS2_ZLIB
case JFFS2_COMPR_MODE_FORCEZLIB:
return "zlib";
+#endif
+#ifdef CONFIG_JFFS2_ZSTD
+ case JFFS2_COMPR_MODE_FORCEZSTD:
+ return "zstd";
#endif
default:
/* should never happen; programmer error */
@@ -174,6 +178,9 @@ static const struct constant_table jffs2_param_compr[] = {
#endif
#ifdef CONFIG_JFFS2_ZLIB
{"zlib", JFFS2_COMPR_MODE_FORCEZLIB },
+#endif
+#ifdef CONFIG_JFFS2_ZSTD
+ {"zstd", JFFS2_COMPR_MODE_FORCEZSTD },
#endif
{}
};
diff --git a/include/uapi/linux/jffs2.h b/include/uapi/linux/jffs2.h
index 784ba0b9690a..af4fb69c8d69 100644
--- a/include/uapi/linux/jffs2.h
+++ b/include/uapi/linux/jffs2.h
@@ -46,6 +46,7 @@
#define JFFS2_COMPR_DYNRUBIN 0x05
#define JFFS2_COMPR_ZLIB 0x06
#define JFFS2_COMPR_LZO 0x07
+#define JFFS2_COMPR_ZSTD 0x08
/* Compatibility flags. */
#define JFFS2_COMPAT_MASK 0xc000 /* What do to if an unknown nodetype is found */
#define JFFS2_NODE_ACCURATE 0x2000
--
2.30.2

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