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u-boot: v2025.10: add btrfs zstd decompression fix
Same patch as v2026.01 — fs/btrfs/compression.c is identical. Tested on Helios4 (Marvell A388). Placed in both board_helios4/ (board-specific BOOTPATCHDIR) and v2025.10/ root (shared, for boards like rockpi-e, orangepi4-lts).
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‎patch/u-boot/v2025.10/board_helios4/general-fix-btrfs-zstd-decompression.patch‎

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Igor Velkov <iav-armbian@draconpern.com>
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Date: Thu, 10 Apr 2026 00:00:00 +0000
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Subject: [PATCH] fs: btrfs: fix zstd decompression for BTRFS extents
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The generic zstd_decompress() wrapper in lib/zstd/zstd.c works for FIT
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images but fails for BTRFS filesystem extents due to two issues:
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1. Sector-aligned compressed size: BTRFS stores compressed extents
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padded to sector boundaries (4096 bytes). The on-disk size
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(disk_num_bytes) may be larger than the actual zstd frame.
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zstd_decompress_dctx() rejects trailing data after the frame,
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causing decompression failures for regular (non-inline) extents.
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2. Sector-aligned decompressed size: BTRFS compresses in sector-sized
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blocks, so the zstd frame content size may exceed the actual data
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size (ram_bytes) stored in extent metadata. For example, a 3906
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byte file is compressed as a 4096 byte block. When the output
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buffer is sized to ram_bytes, zstd_decompress_dctx() fails with
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ZSTD_error_dstSize_tooSmall (error 70) for inline extents.
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Both issues manifest as boot failures on zstd-compressed BTRFS:
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zstd_decompress: failed to decompress: 70
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BTRFS: An error occurred while reading file /boot/boot.scr
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Fix by calling zstd_decompress_dctx() directly with two adjustments:
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- Use zstd_find_frame_compressed_size() to strip sector padding from
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the input, giving zstd the exact frame size.
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- Use ZSTD_getFrameContentSize() to detect when the frame decompresses
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to more than dlen bytes, and allocate a temporary buffer for the
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full decompressed frame when needed.
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This is consistent with decompress_lzo() and decompress_zlib() which
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also call their library functions directly without generic wrappers.
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Signed-off-by: Igor Velkov <iav-armbian@draconpern.com>
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---
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fs/btrfs/compression.c | 66 +++++++++++++++++++++++++++++++++++++++++++----
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1 file changed, 62 insertions(+), 4 deletions(-)
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diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
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--- a/fs/btrfs/compression.c
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+++ b/fs/btrfs/compression.c
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@@ -137,12 +137,70 @@
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static u32 decompress_zstd(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen)
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{
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- struct abuf in, out;
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+ zstd_dctx *ctx;
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+ size_t wsize, ret, frame_csize, out_len;
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+ void *workspace;
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+ unsigned long long fcs;
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+ u8 *tmp = NULL;
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+ u8 *out_buf = dbuf;
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+
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+ out_len = dlen;
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- abuf_init_set(&in, (u8 *)cbuf, clen);
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- abuf_init_set(&out, dbuf, dlen);
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+ /*
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+ * Find the actual compressed frame size. BTRFS stores compressed
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+ * extents padded to sector boundaries, but zstd_decompress_dctx()
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+ * requires the exact frame size without trailing padding.
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+ */
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+ frame_csize = zstd_find_frame_compressed_size(cbuf, clen);
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+ if (!zstd_is_error(frame_csize))
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+ clen = frame_csize;
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- return zstd_decompress(&in, &out);
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+ /*
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+ * BTRFS compresses in sector-sized blocks, so the zstd frame may
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+ * decompress to a full sector (e.g. 4096) even when the actual
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+ * data (ram_bytes) is smaller. Allocate a larger buffer when needed
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+ * to avoid ZSTD_error_dstSize_tooSmall.
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+ */
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+ fcs = ZSTD_getFrameContentSize(cbuf, clen);
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+ if (fcs != ZSTD_CONTENTSIZE_ERROR &&
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+ fcs != ZSTD_CONTENTSIZE_UNKNOWN && fcs > dlen) {
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+ if (fcs > SIZE_MAX)
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+ return -1;
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+ tmp = malloc(fcs);
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+ if (!tmp)
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+ return -1;
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+ out_buf = tmp;
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+ out_len = fcs;
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+ }
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+
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+ wsize = zstd_dctx_workspace_bound();
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+ workspace = malloc(wsize);
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+ if (!workspace) {
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+ free(tmp);
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+ return -1;
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+ }
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+
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+ ctx = zstd_init_dctx(workspace, wsize);
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+ if (!ctx) {
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+ free(workspace);
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+ free(tmp);
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+ return -1;
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+ }
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+
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+ ret = zstd_decompress_dctx(ctx, out_buf, out_len, cbuf, clen);
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+ free(workspace);
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+
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+ if (zstd_is_error(ret)) {
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+ free(tmp);
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+ return -1;
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+ }
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+
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+ if (tmp) {
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+ memcpy(dbuf, tmp, dlen);
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+ free(tmp);
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+ }
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+
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+ return dlen;
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}
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u32 btrfs_decompress(u8 type, const char *c, u32 clen, char *d, u32 dlen)

‎patch/u-boot/v2025.10/general-fix-btrfs-zstd-decompression.patch‎

Lines changed: 119 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,119 @@
1+
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
2+
From: Igor Velkov <iav-armbian@draconpern.com>
3+
Date: Thu, 10 Apr 2026 00:00:00 +0000
4+
Subject: [PATCH] fs: btrfs: fix zstd decompression for BTRFS extents
5+
6+
The generic zstd_decompress() wrapper in lib/zstd/zstd.c works for FIT
7+
images but fails for BTRFS filesystem extents due to two issues:
8+
9+
1. Sector-aligned compressed size: BTRFS stores compressed extents
10+
padded to sector boundaries (4096 bytes). The on-disk size
11+
(disk_num_bytes) may be larger than the actual zstd frame.
12+
zstd_decompress_dctx() rejects trailing data after the frame,
13+
causing decompression failures for regular (non-inline) extents.
14+
15+
2. Sector-aligned decompressed size: BTRFS compresses in sector-sized
16+
blocks, so the zstd frame content size may exceed the actual data
17+
size (ram_bytes) stored in extent metadata. For example, a 3906
18+
byte file is compressed as a 4096 byte block. When the output
19+
buffer is sized to ram_bytes, zstd_decompress_dctx() fails with
20+
ZSTD_error_dstSize_tooSmall (error 70) for inline extents.
21+
22+
Both issues manifest as boot failures on zstd-compressed BTRFS:
23+
24+
zstd_decompress: failed to decompress: 70
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BTRFS: An error occurred while reading file /boot/boot.scr
26+
27+
Fix by calling zstd_decompress_dctx() directly with two adjustments:
28+
- Use zstd_find_frame_compressed_size() to strip sector padding from
29+
the input, giving zstd the exact frame size.
30+
- Use ZSTD_getFrameContentSize() to detect when the frame decompresses
31+
to more than dlen bytes, and allocate a temporary buffer for the
32+
full decompressed frame when needed.
33+
34+
This is consistent with decompress_lzo() and decompress_zlib() which
35+
also call their library functions directly without generic wrappers.
36+
37+
Signed-off-by: Igor Velkov <iav-armbian@draconpern.com>
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---
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fs/btrfs/compression.c | 66 +++++++++++++++++++++++++++++++++++++++++++----
40+
1 file changed, 62 insertions(+), 4 deletions(-)
41+
42+
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
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--- a/fs/btrfs/compression.c
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+++ b/fs/btrfs/compression.c
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@@ -137,12 +137,70 @@
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static u32 decompress_zstd(const u8 *cbuf, u32 clen, u8 *dbuf, u32 dlen)
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{
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- struct abuf in, out;
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+ zstd_dctx *ctx;
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+ size_t wsize, ret, frame_csize, out_len;
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+ void *workspace;
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+ unsigned long long fcs;
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+ u8 *tmp = NULL;
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+ u8 *out_buf = dbuf;
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+
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+ out_len = dlen;
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- abuf_init_set(&in, (u8 *)cbuf, clen);
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- abuf_init_set(&out, dbuf, dlen);
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+ /*
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+ * Find the actual compressed frame size. BTRFS stores compressed
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+ * extents padded to sector boundaries, but zstd_decompress_dctx()
64+
+ * requires the exact frame size without trailing padding.
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+ */
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+ frame_csize = zstd_find_frame_compressed_size(cbuf, clen);
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+ if (!zstd_is_error(frame_csize))
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+ clen = frame_csize;
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- return zstd_decompress(&in, &out);
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+ /*
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+ * BTRFS compresses in sector-sized blocks, so the zstd frame may
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+ * decompress to a full sector (e.g. 4096) even when the actual
74+
+ * data (ram_bytes) is smaller. Allocate a larger buffer when needed
75+
+ * to avoid ZSTD_error_dstSize_tooSmall.
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+ */
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+ fcs = ZSTD_getFrameContentSize(cbuf, clen);
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+ if (fcs != ZSTD_CONTENTSIZE_ERROR &&
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+ fcs != ZSTD_CONTENTSIZE_UNKNOWN && fcs > dlen) {
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+ if (fcs > SIZE_MAX)
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+ return -1;
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+ tmp = malloc(fcs);
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+ if (!tmp)
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+ return -1;
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+ out_buf = tmp;
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+ out_len = fcs;
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+ }
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+
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+ wsize = zstd_dctx_workspace_bound();
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+ workspace = malloc(wsize);
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+ if (!workspace) {
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+ free(tmp);
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+ return -1;
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+ }
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+
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+ ctx = zstd_init_dctx(workspace, wsize);
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+ if (!ctx) {
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+ free(workspace);
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+ free(tmp);
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+ return -1;
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+ }
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+
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+ ret = zstd_decompress_dctx(ctx, out_buf, out_len, cbuf, clen);
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+ free(workspace);
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+
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+ if (zstd_is_error(ret)) {
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+ free(tmp);
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+ return -1;
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+ }
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+
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+ if (tmp) {
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+ memcpy(dbuf, tmp, dlen);
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+ free(tmp);
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+ }
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+
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+ return dlen;
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}
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u32 btrfs_decompress(u8 type, const char *c, u32 clen, char *d, u32 dlen)

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