lib: zstd: export API needed for dictionary support

Patch series "zram: introduce custom comp backends API", v7.

This series introduces support for run-time compression algorithms tuning,
so users, for instance, can adjust compression/acceleration levels and
provide pre-trained compression/decompression dictionaries which certain
algorithms support.

At this point we stop supporting (old/deprecated) comp API. We may add
new acomp API support in the future, but before that zram needs to undergo
some major rework (we are not ready for async compression).

Some benchmarks for reference (look at column #2)

*** init zstd
/sys/block/zram0/mm_stat
1750659072 504622188 514355200 0 514355200 1 0 34204 34204

*** init zstd dict=/home/ss/zstd-dict-amd64
/sys/block/zram0/mm_stat
1750650880 465908890 475398144 0 475398144 1 0 34185 34185

*** init zstd level=8 dict=/home/ss/zstd-dict-amd64
/sys/block/zram0/mm_stat
1750654976 430803319 439873536 0 439873536 1 0 34185 34185

*** init lz4
/sys/block/zram0/mm_stat
1750646784 664266564 677060608 0 677060608 1 0 34288 34288

*** init lz4 dict=/home/ss/lz4-dict-amd64
/sys/block/zram0/mm_stat
1750650880 619990300 632102912 0 632102912 1 0 34278 34278

*** init lz4hc
/sys/block/zram0/mm_stat
1750630400 609023822 621232128 0 621232128 1 0 34288 34288

*** init lz4hc dict=/home/ss/lz4-dict-amd64
/sys/block/zram0/mm_stat
1750659072 505133172 515231744 0 515231744 1 0 34278 34278


Recompress
init zram zstd (prio=0), zstd level=5 (prio 1), zstd with dict (prio 2)

*** zstd
/sys/block/zram0/mm_stat
1750982656 504630584 514269184 0 514269184 1 0 34204 34204

*** idle recompress priority=1 (zstd level=5)
/sys/block/zram0/mm_stat
1750982656 488645601 525438976 0 514269184 1 0 34204 34204

*** idle recompress priority=2 (zstd dict)
/sys/block/zram0/mm_stat
1750982656 460869640 517914624 0 514269184 1 0 34185 34204


This patch (of 24):

We need to export a number of API functions that enable advanced zstd
usage - C/D dictionaries, dictionaries sharing between contexts, etc.

Link: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Sergey Senozhatsky <[e-mail]>
Cc: Nick Terrell <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Cc: Sergey Senozhatsky <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/linux/zstd.h

···
  */
 int zstd_max_clevel(void);
 
+/**
+ * zstd_default_clevel() - default compression level
+ *
+ * Return: Default compression level.
+ */
+int zstd_default_clevel(void);
+
+/**
+ * struct zstd_custom_mem - custom memory allocation
+ */
+typedef ZSTD_customMem zstd_custom_mem;
+
+/**
+ * struct zstd_dict_load_method - Dictionary load method.
+ * See zstd_lib.h.
+ */
+typedef ZSTD_dictLoadMethod_e zstd_dict_load_method;
+
+/**
+ * struct zstd_dict_content_type - Dictionary context type.
+ * See zstd_lib.h.
+ */
+typedef ZSTD_dictContentType_e zstd_dict_content_type;
+
 /* ======   Parameter Selection   ====== */
 
 /**
···
 zstd_parameters zstd_get_params(int level,
 	unsigned long long estimated_src_size);
 
+
+/**
+ * zstd_get_cparams() - returns zstd_compression_parameters for selected level
+ * @level:              The compression level
+ * @estimated_src_size: The estimated source size to compress or 0
+ *                      if unknown.
+ * @dict_size:          Dictionary size.
+ *
+ * Return:              The selected zstd_compression_parameters.
+ */
+zstd_compression_parameters zstd_get_cparams(int level,
+	unsigned long long estimated_src_size, size_t dict_size);
+
 /* ======   Single-pass Compression   ====== */
 
 typedef ZSTD_CCtx zstd_cctx;
···
 size_t zstd_compress_cctx(zstd_cctx *cctx, void *dst, size_t dst_capacity,
 	const void *src, size_t src_size, const zstd_parameters *parameters);
 
+/**
+ * zstd_create_cctx_advanced() - Create compression context
+ * @custom_mem:   Custom allocator.
+ *
+ * Return:        NULL on error, pointer to compression context otherwise.
+ */
+zstd_cctx *zstd_create_cctx_advanced(zstd_custom_mem custom_mem);
+
+/**
+ * zstd_free_cctx() - Free compression context
+ * @cdict:        Pointer to compression context.
+ *
+ * Return:        Always 0.
+ */
+size_t zstd_free_cctx(zstd_cctx* cctx);
+
+/**
+ * struct zstd_cdict - Compression dictionary.
+ * See zstd_lib.h.
+ */
+typedef ZSTD_CDict zstd_cdict;
+
+/**
+ * zstd_create_cdict_byreference() - Create compression dictionary
+ * @dict:              Pointer to dictionary buffer.
+ * @dict_size:         Size of the dictionary buffer.
+ * @dict_load_method:  Dictionary load method.
+ * @dict_content_type: Dictionary content type.
+ * @custom_mem:        Memory allocator.
+ *
+ * Note, this uses @dict by reference (ZSTD_dlm_byRef), so it should be
+ * free before zstd_cdict is destroyed.
+ *
+ * Return:             NULL on error, pointer to compression dictionary
+ *                     otherwise.
+ */
+zstd_cdict *zstd_create_cdict_byreference(const void *dict, size_t dict_size,
+					  zstd_compression_parameters cparams,
+					  zstd_custom_mem custom_mem);
+
+/**
+ * zstd_free_cdict() - Free compression dictionary
+ * @cdict:        Pointer to compression dictionary.
+ *
+ * Return:        Always 0.
+ */
+size_t zstd_free_cdict(zstd_cdict* cdict);
+
+/**
+ * zstd_compress_using_cdict() - compress src into dst using a dictionary
+ * @cctx:         The context. Must have been initialized with zstd_init_cctx().
+ * @dst:          The buffer to compress src into.
+ * @dst_capacity: The size of the destination buffer. May be any size, but
+ *                ZSTD_compressBound(srcSize) is guaranteed to be large enough.
+ * @src:          The data to compress.
+ * @src_size:     The size of the data to compress.
+ * @cdict:        The dictionary to be used.
+ *
+ * Return:        The compressed size or an error, which can be checked using
+ *                zstd_is_error().
+ */
+size_t zstd_compress_using_cdict(zstd_cctx *cctx, void *dst,
+	size_t dst_capacity, const void *src, size_t src_size,
+	const zstd_cdict *cdict);
+
 /* ======   Single-pass Decompression   ====== */
 
 typedef ZSTD_DCtx zstd_dctx;
···
  */
 size_t zstd_decompress_dctx(zstd_dctx *dctx, void *dst, size_t dst_capacity,
 	const void *src, size_t src_size);
+
+/**
+ * struct zstd_ddict - Decompression dictionary.
+ * See zstd_lib.h.
+ */
+typedef ZSTD_DDict zstd_ddict;
+
+/**
+ * zstd_create_ddict_byreference() - Create decompression dictionary
+ * @dict:              Pointer to dictionary buffer.
+ * @dict_size:         Size of the dictionary buffer.
+ * @dict_load_method:  Dictionary load method.
+ * @dict_content_type: Dictionary content type.
+ * @custom_mem:        Memory allocator.
+ *
+ * Note, this uses @dict by reference (ZSTD_dlm_byRef), so it should be
+ * free before zstd_ddict is destroyed.
+ *
+ * Return:             NULL on error, pointer to decompression dictionary
+ *                     otherwise.
+ */
+zstd_ddict *zstd_create_ddict_byreference(const void *dict, size_t dict_size,
+					  zstd_custom_mem custom_mem);
+/**
+ * zstd_free_ddict() - Free decompression dictionary
+ * @dict:         Pointer to the dictionary.
+ *
+ * Return:        Always 0.
+ */
+size_t zstd_free_ddict(zstd_ddict *ddict);
+
+/**
+ * zstd_create_dctx_advanced() - Create decompression context
+ * @custom_mem:   Custom allocator.
+ *
+ * Return:        NULL on error, pointer to decompression context otherwise.
+ */
+zstd_dctx *zstd_create_dctx_advanced(zstd_custom_mem custom_mem);
+
+/**
+ * zstd_free_dctx() -- Free decompression context
+ * @dctx:         Pointer to decompression context.
+ * Return:        Always 0.
+ */
+size_t zstd_free_dctx(zstd_dctx *dctx);
+
+/**
+ * zstd_decompress_using_ddict() - decompress src into dst using a dictionary
+ * @dctx:         The decompression context.
+ * @dst:          The buffer to decompress src into.
+ * @dst_capacity: The size of the destination buffer. Must be at least as large
+ *                as the decompressed size. If the caller cannot upper bound the
+ *                decompressed size, then it's better to use the streaming API.
+ * @src:          The zstd compressed data to decompress. Multiple concatenated
+ *                frames and skippable frames are allowed.
+ * @src_size:     The exact size of the data to decompress.
+ * @ddict:        The dictionary to be used.
+ *
+ * Return:        The decompressed size or an error, which can be checked using
+ *                zstd_is_error().
+ */
+size_t zstd_decompress_using_ddict(zstd_dctx *dctx,
+	void *dst, size_t dst_capacity, const void *src, size_t src_size,
+	const zstd_ddict *ddict);
+
 
 /* ======   Streaming Buffers   ====== */
 

lib/zstd/zstd_compress_module.c

···
 }
 EXPORT_SYMBOL(zstd_max_clevel);
 
+int zstd_default_clevel(void)
+{
+	return ZSTD_defaultCLevel();
+}
+EXPORT_SYMBOL(zstd_default_clevel);
+
 size_t zstd_compress_bound(size_t src_size)
 {
 	return ZSTD_compressBound(src_size);
···
 	return ZSTD_getParams(level, estimated_src_size, 0);
 }
 EXPORT_SYMBOL(zstd_get_params);
+
+zstd_compression_parameters zstd_get_cparams(int level,
+	unsigned long long estimated_src_size, size_t dict_size)
+{
+	return ZSTD_getCParams(level, estimated_src_size, dict_size);
+}
+EXPORT_SYMBOL(zstd_get_cparams);
 
 size_t zstd_cctx_workspace_bound(const zstd_compression_parameters *cparams)
 {
···
 }
 EXPORT_SYMBOL(zstd_init_cctx);
 
+zstd_cctx *zstd_create_cctx_advanced(zstd_custom_mem custom_mem)
+{
+	return ZSTD_createCCtx_advanced(custom_mem);
+}
+EXPORT_SYMBOL(zstd_create_cctx_advanced);
+
+size_t zstd_free_cctx(zstd_cctx *cctx)
+{
+	return ZSTD_freeCCtx(cctx);
+}
+EXPORT_SYMBOL(zstd_free_cctx);
+
+zstd_cdict *zstd_create_cdict_byreference(const void *dict, size_t dict_size,
+					  zstd_compression_parameters cparams,
+					  zstd_custom_mem custom_mem)
+{
+	return ZSTD_createCDict_advanced(dict, dict_size, ZSTD_dlm_byRef,
+					 ZSTD_dct_auto, cparams, custom_mem);
+}
+EXPORT_SYMBOL(zstd_create_cdict_byreference);
+
+size_t zstd_free_cdict(zstd_cdict *cdict)
+{
+	return ZSTD_freeCDict(cdict);
+}
+EXPORT_SYMBOL(zstd_free_cdict);
+
 size_t zstd_compress_cctx(zstd_cctx *cctx, void *dst, size_t dst_capacity,
 	const void *src, size_t src_size, const zstd_parameters *parameters)
 {
···
 	return ZSTD_compress2(cctx, dst, dst_capacity, src, src_size);
 }
 EXPORT_SYMBOL(zstd_compress_cctx);
+
+size_t zstd_compress_using_cdict(zstd_cctx *cctx, void *dst,
+	size_t dst_capacity, const void *src, size_t src_size,
+	const ZSTD_CDict *cdict)
+{
+	return ZSTD_compress_usingCDict(cctx, dst, dst_capacity,
+					src, src_size, cdict);
+}
+EXPORT_SYMBOL(zstd_compress_using_cdict);
 
 size_t zstd_cstream_workspace_bound(const zstd_compression_parameters *cparams)
 {

lib/zstd/zstd_decompress_module.c

···
 }
 EXPORT_SYMBOL(zstd_dctx_workspace_bound);
 
+zstd_dctx *zstd_create_dctx_advanced(zstd_custom_mem custom_mem)
+{
+	return ZSTD_createDCtx_advanced(custom_mem);
+}
+EXPORT_SYMBOL(zstd_create_dctx_advanced);
+
+size_t zstd_free_dctx(zstd_dctx *dctx)
+{
+	return ZSTD_freeDCtx(dctx);
+}
+EXPORT_SYMBOL(zstd_free_dctx);
+
+zstd_ddict *zstd_create_ddict_byreference(const void *dict, size_t dict_size,
+					  zstd_custom_mem custom_mem)
+{
+	return ZSTD_createDDict_advanced(dict, dict_size, ZSTD_dlm_byRef,
+					 ZSTD_dct_auto, custom_mem);
+
+}
+EXPORT_SYMBOL(zstd_create_ddict_byreference);
+
+size_t zstd_free_ddict(zstd_ddict *ddict)
+{
+	return ZSTD_freeDDict(ddict);
+}
+EXPORT_SYMBOL(zstd_free_ddict);
+
 zstd_dctx *zstd_init_dctx(void *workspace, size_t workspace_size)
 {
 	if (workspace == NULL)
···
 	return ZSTD_decompressDCtx(dctx, dst, dst_capacity, src, src_size);
 }
 EXPORT_SYMBOL(zstd_decompress_dctx);
+
+size_t zstd_decompress_using_ddict(zstd_dctx *dctx,
+	void *dst, size_t dst_capacity, const void* src, size_t src_size,
+	const zstd_ddict* ddict)
+{
+	return ZSTD_decompress_usingDDict(dctx, dst, dst_capacity, src,
+					  src_size, ddict);
+}
+EXPORT_SYMBOL(zstd_decompress_using_ddict);
 
 size_t zstd_dstream_workspace_bound(size_t max_window_size)
 {