lib: zstd: Upgrade to latest upstream zstd version 1.4.6

Upgrade to the latest upstream zstd version 1.4.6.

This patch is 100% generated from upstream zstd commit 2fb09ad48201 [0].

This patch is very large because it is transitioning from the custom
kernel zstd to using upstream directly. The new zstd follows upstreams
file structure which is different. Future update patches will be much
smaller because they will only contain the changes from one upstream
zstd release.

As an aid for review I've created a commit [1] that shows the diff
between upstream zstd as-is (which doesn't compile), and the zstd
code imported in this patch. The verion of zstd in this patch is
generated from upstream with changes applied by automation to replace
upstreams libc dependencies, remove unnecessary portability macros,
and use the kernel's xxhash instead of bundling it.

The benefits of this patch are as follows:
1. Using upstream directly with automated script to generate kernel
   code. This allows us to update the kernel every upstream release, so
   the kernel gets the latest bug fixes and performance improvements,
   and doesn't get 3 years out of date again. The automation and the
   translated code are tested every upstream commit to ensure it
   continues to work.
2. Upgrades from a custom zstd based on 1.3.1 to 1.4.6, getting 3 years
   of performance improvements and bug fixes. On x86_64 I've measured
   15% faster BtrFS and SquashFS decompression+read speeds, 35% faster
   kernel decompression, and 30% faster ZRAM decompression+read speeds.
   Additionally, the latest zstd uses ~1 KB less stack space for
   compression.
3. Switches to using the upstream API directly. It is slightly less
   ergonomic for the kernel use case, where malloc/free aren't provided.
   But, it means that users don't need to familiarize themselves with 2
   zstd APIs.

I chose the bulk update instead of replaying upstream commits because
there have been ~3500 upstream commits since the 1.3.1 release, zstd
wasn't ready to be used in the kernel as-is before a month ago, and not
all upstream zstd commits build. The bulk update preserves bisectablity
because bugs can be bisected to the zstd version update. At that point
the update can be reverted, and we can work with upstream to find and
fix the bug.

Note that upstream zstd release 1.4.6 doesn't exist yet. I have cut a
staging branch at 2fb09ad48201 [0] and will apply any changes requested
to the staging branch. Once we're ready to merge this update I will cut
a zstd release at the commit we merge, so we have a known zstd release
in the kernel.

[0] facebook/zstd@2fb09ad
[1] terrelln@47b52ad

Signed-off-by: Nick Terrell <terrelln@fb.com>

include/linux/zstd_errors.h

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2016-2020, Yann Collet, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ * You may select, at your option, one of the above-listed licenses.
+ */
+
+#ifndef ZSTD_ERRORS_H_398273423
+#define ZSTD_ERRORS_H_398273423
+
+
+/*===== dependency =====*/
+#include <linux/types.h>   /* size_t */
+
+
+/* =====   ZSTDERRORLIB_API : control library symbols visibility   ===== */
+#define ZSTDERRORLIB_VISIBILITY 
+#define ZSTDERRORLIB_API ZSTDERRORLIB_VISIBILITY
+
+/*-*********************************************
+ *  Error codes list
+ *-*********************************************
+ *  Error codes _values_ are pinned down since v1.3.1 only.
+ *  Therefore, don't rely on values if you may link to any version < v1.3.1.
+ *
+ *  Only values < 100 are considered stable.
+ *
+ *  note 1 : this API shall be used with static linking only.
+ *           dynamic linking is not yet officially supported.
+ *  note 2 : Prefer relying on the enum than on its value whenever possible
+ *           This is the only supported way to use the error list < v1.3.1
+ *  note 3 : ZSTD_isError() is always correct, whatever the library version.
+ **********************************************/
+typedef enum {
+  ZSTD_error_no_error = 0,
+  ZSTD_error_GENERIC  = 1,
+  ZSTD_error_prefix_unknown                = 10,
+  ZSTD_error_version_unsupported           = 12,
+  ZSTD_error_frameParameter_unsupported    = 14,
+  ZSTD_error_frameParameter_windowTooLarge = 16,
+  ZSTD_error_corruption_detected = 20,
+  ZSTD_error_checksum_wrong      = 22,
+  ZSTD_error_dictionary_corrupted      = 30,
+  ZSTD_error_dictionary_wrong          = 32,
+  ZSTD_error_dictionaryCreation_failed = 34,
+  ZSTD_error_parameter_unsupported   = 40,
+  ZSTD_error_parameter_outOfBound    = 42,
+  ZSTD_error_tableLog_tooLarge       = 44,
+  ZSTD_error_maxSymbolValue_tooLarge = 46,
+  ZSTD_error_maxSymbolValue_tooSmall = 48,
+  ZSTD_error_stage_wrong       = 60,
+  ZSTD_error_init_missing      = 62,
+  ZSTD_error_memory_allocation = 64,
+  ZSTD_error_workSpace_tooSmall= 66,
+  ZSTD_error_dstSize_tooSmall = 70,
+  ZSTD_error_srcSize_wrong    = 72,
+  ZSTD_error_dstBuffer_null   = 74,
+  /* following error codes are __NOT STABLE__, they can be removed or changed in future versions */
+  ZSTD_error_frameIndex_tooLarge = 100,
+  ZSTD_error_seekableIO          = 102,
+  ZSTD_error_dstBuffer_wrong     = 104,
+  ZSTD_error_maxCode = 120  /* never EVER use this value directly, it can change in future versions! Use ZSTD_isError() instead */
+} ZSTD_ErrorCode;
+
+/*! ZSTD_getErrorCode() :
+    convert a `size_t` function result into a `ZSTD_ErrorCode` enum type,
+    which can be used to compare with enum list published above */
+ZSTDERRORLIB_API ZSTD_ErrorCode ZSTD_getErrorCode(size_t functionResult);
+ZSTDERRORLIB_API const char* ZSTD_getErrorString(ZSTD_ErrorCode code);   /**< Same as ZSTD_getErrorName, but using a `ZSTD_ErrorCode` enum argument */
+
+
+
+#endif /* ZSTD_ERRORS_H_398273423 */

lib/zstd/Makefile

@@ -4,7 +4,34 @@ obj-$(CONFIG_ZSTD_DECOMPRESS) += zstd_decompress.o
 
 ccflags-y += -O3
 
-zstd_compress-y := fse_compress.o huf_compress.o compress.o \
-		   entropy_common.o fse_decompress.o zstd_common.o
-zstd_decompress-y := huf_decompress.o decompress.o \
-		     entropy_common.o fse_decompress.o zstd_common.o
+zstd_compress-y := \
+		zstd_compress_module.o \
+		common/debug.o \
+		common/entropy_common.o \
+		common/error_private.o \
+		common/fse_decompress.o \
+		common/zstd_common.o \
+		compress/fse_compress.o \
+		compress/hist.o \
+		compress/huf_compress.o \
+		compress/zstd_compress.o \
+		compress/zstd_compress_literals.o \
+		compress/zstd_compress_sequences.o \
+		compress/zstd_compress_superblock.o \
+		compress/zstd_double_fast.o \
+		compress/zstd_fast.o \
+		compress/zstd_lazy.o \
+		compress/zstd_ldm.o \
+		compress/zstd_opt.o \
+
+zstd_decompress-y := \
+		zstd_decompress_module.o \
+		common/debug.o \
+		common/entropy_common.o \
+		common/error_private.o \
+		common/fse_decompress.o \
+		common/zstd_common.o \
+		decompress/huf_decompress.o \
+		decompress/zstd_ddict.o \
+		decompress/zstd_decompress.o \
+		decompress/zstd_decompress_block.o \