[PATCH] erofs: don't calculate new start when expanding read length

[Yue Hu]

From: Yue Hu <huyue2 at coolpad.com>

We only expand the trailing edge and not the leading edge.  So no need
to obtain new start again.  Let's use the existing ->headoffset instead.

Signed-off-by: Yue Hu <huyue2 at coolpad.com>
---
 fs/erofs/zdata.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 874fee35af32..bab8dcb8e848 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -1828,26 +1828,24 @@ static void z_erofs_pcluster_readmore(struct z_erofs_decompress_frontend *f,
 {
 	struct inode *inode = f->inode;
 	struct erofs_map_blocks *map = &f->map;
-	erofs_off_t cur, end;
+	erofs_off_t cur, end, headoffset = f->headoffset;
 	int err;
 
 	if (backmost) {
 		if (rac)
-			end = f->headoffset + readahead_length(rac) - 1;
+			end = headoffset + readahead_length(rac) - 1;
 		else
-			end = f->headoffset + PAGE_SIZE - 1;
+			end = headoffset + PAGE_SIZE - 1;
 		map->m_la = end;
 		err = z_erofs_map_blocks_iter(inode, map,
 					      EROFS_GET_BLOCKS_READMORE);
 		if (err)
 			return;
 
-		/* expend ra for the trailing edge if readahead */
+		/* expand ra for the trailing edge if readahead */
 		if (rac) {
-			loff_t newstart = readahead_pos(rac);
-
 			cur = round_up(map->m_la + map->m_llen, PAGE_SIZE);
-			readahead_expand(rac, newstart, cur - newstart);
+			readahead_expand(rac, headoffset, cur - headoffset);
 			return;
 		}
 		end = round_up(end, PAGE_SIZE);
-- 
2.17.1