erofs: don't align offset for erofs_read_metabuf() (simple cases)

Most of the callers of erofs_read_metabuf() have the following form:

	block = erofs_blknr(sb, offset);
	off = erofs_blkoff(sb, offset);
	p = erofs_read_metabuf(...., erofs_pos(sb, block), ...);
	if (IS_ERR(p))
		return PTR_ERR(p);
	q = p + off;
	// no further uses of p, block or off.

The value passed to erofs_read_metabuf() is offset rounded down to block
size, i.e. offset - off.  Passing offset as-is would increase the return
value by off in case of success and keep the return value unchanged in
in case of error.  In other words, the same could be achieved by

	q = erofs_read_metabuf(...., offset, ...);
	if (IS_ERR(q))
		return PTR_ERR(q);

This commit convert these simple cases.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/r/20240425195915.GD1031757@ZenIV
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

1 files changed, 3 insertions, 9 deletions

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index ac618b3484f1..fda16eedafb5 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -273,21 +273,15 @@ static int erofs_fscache_data_read_slice(struct erofs_fscache_rq *req)
 	if (map.m_flags & EROFS_MAP_META) {
 		struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
 		struct iov_iter iter;
-		erofs_blk_t blknr;
-		size_t offset, size;
+		size_t size = map.m_llen;
 		void *src;
 
-		/* For tail packing layout, the offset may be non-zero. */
-		offset = erofs_blkoff(sb, map.m_pa);
-		blknr = erofs_blknr(sb, map.m_pa);
-		size = map.m_llen;
-
-		src = erofs_read_metabuf(&buf, sb, erofs_pos(sb, blknr), EROFS_KMAP);
+		src = erofs_read_metabuf(&buf, sb, map.m_pa, EROFS_KMAP);
 		if (IS_ERR(src))
 			return PTR_ERR(src);
 
 		iov_iter_xarray(&iter, ITER_DEST, &mapping->i_pages, pos, PAGE_SIZE);
-		if (copy_to_iter(src + offset, size, &iter) != size) {
+		if (copy_to_iter(src, size, &iter) != size) {
 			erofs_put_metabuf(&buf);
 			return -EFAULT;
 		}