[PATCH 4/8] erofs-utils: mkfs: support interlaced uncompressed data layout

[Gao Xiang]

From: Yue Hu <huyue2 at coolpad.com>

Interlaced uncompressed data can minimize unnecessary data processing
by using in-place I/O.

However it cannot be used together with deduplication.

Signed-off-by: Yue Hu <huyue2 at coolpad.com>
Signed-off-by: Gao Xiang <hsiangkao at linux.alibaba.com>
---
 lib/compress.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/lib/compress.c b/lib/compress.c
index 3c1d9db..8fa60e2 100644
--- a/lib/compress.c
+++ b/lib/compress.c
@@ -150,7 +150,7 @@ static int write_uncompressed_extent(struct z_erofs_vle_compress_ctx *ctx,
 				     unsigned int *len, char *dst)
 {
 	int ret;
-	unsigned int count;
+	unsigned int count, interlaced_offset, rightpart;
 
 	/* reset clusterofs to 0 if permitted */
 	if (!erofs_sb_has_lz4_0padding() && ctx->clusterofs &&
@@ -160,11 +160,16 @@ static int write_uncompressed_extent(struct z_erofs_vle_compress_ctx *ctx,
 		ctx->clusterofs = 0;
 	}
 
-	/* write uncompressed data */
 	count = min(EROFS_BLKSIZ, *len);
 
-	memcpy(dst, ctx->queue + ctx->head, count);
-	memset(dst + count, 0, EROFS_BLKSIZ - count);
+	/* write interlaced uncompressed data if needed */
+	interlaced_offset = 0; /* will set it to clusterofs */
+	rightpart = min(EROFS_BLKSIZ - interlaced_offset, count);
+
+	memset(dst, 0, EROFS_BLKSIZ);
+
+	memcpy(dst + interlaced_offset, ctx->queue + ctx->head, rightpart);
+	memcpy(dst, ctx->queue + ctx->head + rightpart, count - rightpart);
 
 	erofs_dbg("Writing %u uncompressed data to block %u",
 		  count, ctx->blkaddr);
-- 
2.24.4