[RFC PATCH v8 1/4] erofs-utils: fuse: support interlaced uncompressed pcluster

[Yue Hu <zbestahu@gmail.com>]

From: Yue Hu <huyue2@coolpad.com>

Support uncompressed data layout with on-disk interlaced offset in
compression mode for erofsfuse.

Signed-off-by: Yue Hu <huyue2@coolpad.com>
---
 include/erofs/decompress.h |  3 +++
 include/erofs_fs.h         |  2 ++
 lib/data.c                 |  8 +++++++-
 lib/decompress.c           | 17 +++++++++++++++--
 4 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/include/erofs/decompress.h b/include/erofs/decompress.h
index 82bf7b8..a9067cb 100644
--- a/include/erofs/decompress.h
+++ b/include/erofs/decompress.h
@@ -23,6 +23,9 @@ struct z_erofs_decompress_req {
 	unsigned int decodedskip;
 	unsigned int inputsize, decodedlength;
 
+	/* cut point of interlaced uncompressed data */
+	unsigned int interlaced_offset;
+
 	/* indicate the algorithm will be used for decompression */
 	unsigned int alg;
 	bool partial_decoding;
diff --git a/include/erofs_fs.h b/include/erofs_fs.h
index 08f9761..b8a7421 100644
--- a/include/erofs_fs.h
+++ b/include/erofs_fs.h
@@ -294,11 +294,13 @@ struct z_erofs_lzma_cfgs {
  * bit 1 : HEAD1 big pcluster (0 - off; 1 - on)
  * bit 2 : HEAD2 big pcluster (0 - off; 1 - on)
  * bit 3 : tailpacking inline pcluster (0 - off; 1 - on)
+ * bit 4 : interlaced plain pcluster (0 - off; 1 - on)
  */
 #define Z_EROFS_ADVISE_COMPACTED_2B		0x0001
 #define Z_EROFS_ADVISE_BIG_PCLUSTER_1		0x0002
 #define Z_EROFS_ADVISE_BIG_PCLUSTER_2		0x0004
 #define Z_EROFS_ADVISE_INLINE_PCLUSTER		0x0008
+#define Z_EROFS_ADVISE_INTERLACED_PCLUSTER	0x0010
 
 struct z_erofs_map_header {
 	__le16	h_reserved1;
diff --git a/lib/data.c b/lib/data.c
index ad7b2cb..2d76816 100644
--- a/lib/data.c
+++ b/lib/data.c
@@ -226,7 +226,7 @@ static int z_erofs_read_data(struct erofs_inode *inode, char *buffer,
 	};
 	struct erofs_map_dev mdev;
 	bool partial;
-	unsigned int bufsize = 0;
+	unsigned int bufsize = 0, interlaced_offset;
 	char *raw = NULL;
 	int ret = 0;
 
@@ -287,10 +287,16 @@ static int z_erofs_read_data(struct erofs_inode *inode, char *buffer,
 		if (ret < 0)
 			break;
 
+		interlaced_offset = 0;
+		if ((inode->z_advise & Z_EROFS_ADVISE_INTERLACED_PCLUSTER) &&
+		    map.m_algorithmformat == Z_EROFS_COMPRESSION_SHIFTED)
+			interlaced_offset = erofs_blkoff(map.m_la);
+
 		ret = z_erofs_decompress(&(struct z_erofs_decompress_req) {
 					.in = raw,
 					.out = buffer + end - offset,
 					.decodedskip = skip,
+					.interlaced_offset = interlaced_offset,
 					.inputsize = map.m_plen,
 					.decodedlength = length,
 					.alg = map.m_algorithmformat,
diff --git a/lib/decompress.c b/lib/decompress.c
index 1661f91..39da555 100644
--- a/lib/decompress.c
+++ b/lib/decompress.c
@@ -132,14 +132,27 @@ out:
 int z_erofs_decompress(struct z_erofs_decompress_req *rq)
 {
 	if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED) {
+		unsigned int count, rightpart, skip;
+
 		if (rq->inputsize > EROFS_BLKSIZ)
 			return -EFSCORRUPTED;
 
 		DBG_BUGON(rq->decodedlength > EROFS_BLKSIZ);
 		DBG_BUGON(rq->decodedlength < rq->decodedskip);
 
-		memcpy(rq->out, rq->in + rq->decodedskip,
-		       rq->decodedlength - rq->decodedskip);
+		count = rq->decodedlength - rq->decodedskip;
+
+		if (rq->interlaced_offset) {
+			skip = erofs_blkoff(rq->interlaced_offset +
+					    rq->decodedskip);
+			rightpart = min(EROFS_BLKSIZ - skip, count);
+		} else {
+			skip = rq->decodedskip;
+			rightpart = count;
+		}
+		memcpy(rq->out, rq->in + skip, rightpart);
+		memcpy(rq->out + rightpart, rq->in, count - rightpart);
+
 		return 0;
 	}
 
-- 
2.17.1