[PATCH] fs/erofs: add DEFLATE algorithm support

[Jianan Huang]

This patch adds DEFLATE compression algorithm support. It's a good choice
to trade off between compression ratios and performance compared to LZ4.
Alternatively, DEFLATE could be used for some specific files since EROFS
supports multiple compression algorithms in one image.

Signed-off-by: Jianan Huang <jnhuang95 at gmail.com>
---
 fs/erofs/Kconfig      | 15 ++++++++
 fs/erofs/decompress.c | 83 +++++++++++++++++++++++++++++++++++++++++++
 fs/erofs/erofs_fs.h   |  1 +
 3 files changed, 99 insertions(+)

diff --git a/fs/erofs/Kconfig b/fs/erofs/Kconfig
index ee4e777c5c..c8463357ca 100644
--- a/fs/erofs/Kconfig
+++ b/fs/erofs/Kconfig
@@ -19,3 +19,18 @@ config FS_EROFS_ZIP
 	help
 	  Enable fixed-sized output compression for EROFS.
 	  If you don't want to enable compression feature, say N.
+
+config FS_EROFS_ZIP_DEFLATE
+	bool "EROFS DEFLATE compressed data support"
+	depends on FS_EROFS_ZIP
+	select ZLIB
+	help
+	  Saying Y here includes support for reading EROFS file systems
+	  containing DEFLATE compressed data.  It gives better compression
+	  ratios than the default LZ4 format, while it costs more CPU
+	  overhead.
+
+	  DEFLATE support is an experimental feature for now and so most
+	  file systems will be readable without selecting this option.
+
+	  If unsure, say N.
diff --git a/fs/erofs/decompress.c b/fs/erofs/decompress.c
index e04e5c34a8..ec74816534 100644
--- a/fs/erofs/decompress.c
+++ b/fs/erofs/decompress.c
@@ -1,6 +1,85 @@
 // SPDX-License-Identifier: GPL-2.0+
 #include "decompress.h"
 
+#if IS_ENABLED(CONFIG_ZLIB)
+#include <u-boot/zlib.h>
+
+/* report a zlib or i/o error */
+static int zerr(int ret)
+{
+	switch (ret) {
+	case Z_STREAM_ERROR:
+		return -EINVAL;
+	case Z_DATA_ERROR:
+		return -EIO;
+	case Z_MEM_ERROR:
+		return -ENOMEM;
+	case Z_ERRNO:
+	default:
+		return -EFAULT;
+	}
+}
+
+static int z_erofs_decompress_deflate(struct z_erofs_decompress_req *rq)
+{
+	u8 *dest = (u8 *)rq->out;
+	u8 *src = (u8 *)rq->in;
+	u8 *buff = NULL;
+	unsigned int inputmargin = 0;
+	z_stream strm;
+	int ret;
+
+	while (!src[inputmargin & (erofs_blksiz() - 1)])
+		if (!(++inputmargin & (erofs_blksiz() - 1)))
+			break;
+
+	if (inputmargin >= rq->inputsize)
+		return -EFSCORRUPTED;
+
+	if (rq->decodedskip) {
+		buff = malloc(rq->decodedlength);
+		if (!buff)
+			return -ENOMEM;
+		dest = buff;
+	}
+
+	/* allocate inflate state */
+	strm.zalloc = Z_NULL;
+	strm.zfree = Z_NULL;
+	strm.opaque = Z_NULL;
+	strm.avail_in = 0;
+	strm.next_in = Z_NULL;
+	ret = inflateInit2(&strm, -15);
+	if (ret != Z_OK) {
+		free(buff);
+		return zerr(ret);
+	}
+
+	strm.next_in = src + inputmargin;
+	strm.avail_in = rq->inputsize - inputmargin;
+	strm.next_out = dest;
+	strm.avail_out = rq->decodedlength;
+
+	ret = inflate(&strm, rq->partial_decoding ? Z_SYNC_FLUSH : Z_FINISH);
+	if (ret != Z_STREAM_END || strm.total_out != rq->decodedlength) {
+		if (ret != Z_OK || !rq->partial_decoding) {
+			ret = zerr(ret);
+			goto out_inflate_end;
+		}
+	}
+
+	if (rq->decodedskip)
+		memcpy(rq->out, dest + rq->decodedskip,
+		       rq->decodedlength - rq->decodedskip);
+
+out_inflate_end:
+	inflateEnd(&strm);
+	if (buff)
+		free(buff);
+	return ret;
+}
+#endif
+
 #if IS_ENABLED(CONFIG_LZ4)
 #include <u-boot/lz4.h>
 static int z_erofs_decompress_lz4(struct z_erofs_decompress_req *rq)
@@ -93,6 +172,10 @@ int z_erofs_decompress(struct z_erofs_decompress_req *rq)
 #if IS_ENABLED(CONFIG_LZ4)
 	if (rq->alg == Z_EROFS_COMPRESSION_LZ4)
 		return z_erofs_decompress_lz4(rq);
+#endif
+#if IS_ENABLED(CONFIG_ZLIB)
+	if (rq->alg == Z_EROFS_COMPRESSION_DEFLATE)
+		return z_erofs_decompress_deflate(rq);
 #endif
 	return -EOPNOTSUPP;
 }
diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
index 158e2c68a1..5bac4fe1a1 100644
--- a/fs/erofs/erofs_fs.h
+++ b/fs/erofs/erofs_fs.h
@@ -304,6 +304,7 @@ enum {
 enum {
 	Z_EROFS_COMPRESSION_LZ4		= 0,
 	Z_EROFS_COMPRESSION_LZMA	= 1,
+	Z_EROFS_COMPRESSION_DEFLATE	= 2,
 	Z_EROFS_COMPRESSION_MAX
 };
 
-- 
2.34.1