v4.19.13 snapshot.
diff --git a/fs/squashfs/zstd_wrapper.c b/fs/squashfs/zstd_wrapper.c
new file mode 100644
index 0000000..eeaabf8
--- /dev/null
+++ b/fs/squashfs/zstd_wrapper.c
@@ -0,0 +1,151 @@
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2,
+ * or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * zstd_wrapper.c
+ */
+
+#include <linux/mutex.h>
+#include <linux/buffer_head.h>
+#include <linux/slab.h>
+#include <linux/zstd.h>
+#include <linux/vmalloc.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs.h"
+#include "decompressor.h"
+#include "page_actor.h"
+
+struct workspace {
+ void *mem;
+ size_t mem_size;
+ size_t window_size;
+};
+
+static void *zstd_init(struct squashfs_sb_info *msblk, void *buff)
+{
+ struct workspace *wksp = kmalloc(sizeof(*wksp), GFP_KERNEL);
+
+ if (wksp == NULL)
+ goto failed;
+ wksp->window_size = max_t(size_t,
+ msblk->block_size, SQUASHFS_METADATA_SIZE);
+ wksp->mem_size = ZSTD_DStreamWorkspaceBound(wksp->window_size);
+ wksp->mem = vmalloc(wksp->mem_size);
+ if (wksp->mem == NULL)
+ goto failed;
+
+ return wksp;
+
+failed:
+ ERROR("Failed to allocate zstd workspace\n");
+ kfree(wksp);
+ return ERR_PTR(-ENOMEM);
+}
+
+
+static void zstd_free(void *strm)
+{
+ struct workspace *wksp = strm;
+
+ if (wksp)
+ vfree(wksp->mem);
+ kfree(wksp);
+}
+
+
+static int zstd_uncompress(struct squashfs_sb_info *msblk, void *strm,
+ struct buffer_head **bh, int b, int offset, int length,
+ struct squashfs_page_actor *output)
+{
+ struct workspace *wksp = strm;
+ ZSTD_DStream *stream;
+ size_t total_out = 0;
+ size_t zstd_err;
+ int k = 0;
+ ZSTD_inBuffer in_buf = { NULL, 0, 0 };
+ ZSTD_outBuffer out_buf = { NULL, 0, 0 };
+
+ stream = ZSTD_initDStream(wksp->window_size, wksp->mem, wksp->mem_size);
+
+ if (!stream) {
+ ERROR("Failed to initialize zstd decompressor\n");
+ goto out;
+ }
+
+ out_buf.size = PAGE_SIZE;
+ out_buf.dst = squashfs_first_page(output);
+
+ do {
+ if (in_buf.pos == in_buf.size && k < b) {
+ int avail = min(length, msblk->devblksize - offset);
+
+ length -= avail;
+ in_buf.src = bh[k]->b_data + offset;
+ in_buf.size = avail;
+ in_buf.pos = 0;
+ offset = 0;
+ }
+
+ if (out_buf.pos == out_buf.size) {
+ out_buf.dst = squashfs_next_page(output);
+ if (out_buf.dst == NULL) {
+ /* Shouldn't run out of pages
+ * before stream is done.
+ */
+ squashfs_finish_page(output);
+ goto out;
+ }
+ out_buf.pos = 0;
+ out_buf.size = PAGE_SIZE;
+ }
+
+ total_out -= out_buf.pos;
+ zstd_err = ZSTD_decompressStream(stream, &out_buf, &in_buf);
+ total_out += out_buf.pos; /* add the additional data produced */
+
+ if (in_buf.pos == in_buf.size && k < b)
+ put_bh(bh[k++]);
+ } while (zstd_err != 0 && !ZSTD_isError(zstd_err));
+
+ squashfs_finish_page(output);
+
+ if (ZSTD_isError(zstd_err)) {
+ ERROR("zstd decompression error: %d\n",
+ (int)ZSTD_getErrorCode(zstd_err));
+ goto out;
+ }
+
+ if (k < b)
+ goto out;
+
+ return (int)total_out;
+
+out:
+ for (; k < b; k++)
+ put_bh(bh[k]);
+
+ return -EIO;
+}
+
+const struct squashfs_decompressor squashfs_zstd_comp_ops = {
+ .init = zstd_init,
+ .free = zstd_free,
+ .decompress = zstd_uncompress,
+ .id = ZSTD_COMPRESSION,
+ .name = "zstd",
+ .supported = 1
+};