[PATCH] erofs: simplify readdir operation

[Hongzhen Luo]

  - Use i_size instead of i_size_read() due to immutable fses;

  - Get rid of an unneeded goto since erofs_fill_dentries() also works;

  - Remove unnecessary lines.

Signed-off-by: Hongzhen Luo<hongzhen at linux.alibaba.com>
---
  fs/erofs/dir.c      | 35 ++++++++++++-----------------------
  fs/erofs/internal.h |  2 +-
  2 files changed, 13 insertions(+), 24 deletions(-)

diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
index 2193a6710c8f..c3b90abdee37 100644
--- a/fs/erofs/dir.c
+++ b/fs/erofs/dir.c
@@ -8,19 +8,15 @@
  
  static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
  			       void *dentry_blk, struct erofs_dirent *de,
-			       unsigned int nameoff, unsigned int maxsize)
+			       unsigned int nameoff0, unsigned int maxsize)
  {
-	const struct erofs_dirent *end = dentry_blk + nameoff;
+	const struct erofs_dirent *end = dentry_blk + nameoff0;
  
  	while (de < end) {
-		const char *de_name;
+		unsigned char d_type = fs_ftype_to_dtype(de->file_type);
+		unsigned int nameoff = le16_to_cpu(de->nameoff);
+		const char *de_name = (char *)dentry_blk + nameoff;
  		unsigned int de_namelen;
-		unsigned char d_type;
-
-		d_type = fs_ftype_to_dtype(de->file_type);
-
-		nameoff = le16_to_cpu(de->nameoff);
-		de_name = (char *)dentry_blk + nameoff;
  
  		/* the last dirent in the block? */
  		if (de + 1 >= end)
@@ -52,21 +48,20 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
  	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
  	struct super_block *sb = dir->i_sb;
  	unsigned long bsz = sb->s_blocksize;
-	const size_t dirsize = i_size_read(dir);
-	unsigned int i = erofs_blknr(sb, ctx->pos);
  	unsigned int ofs = erofs_blkoff(sb, ctx->pos);
  	int err = 0;
  	bool initial = true;
  
  	buf.mapping = dir->i_mapping;
-	while (ctx->pos < dirsize) {
+	while (ctx->pos < dir->i_size) {
+		erofs_off_t dbstart = ctx->pos - ofs;
  		struct erofs_dirent *de;
  		unsigned int nameoff, maxsize;
  
-		de = erofs_bread(&buf, erofs_pos(sb, i), EROFS_KMAP);
+		de = erofs_bread(&buf, dbstart, EROFS_KMAP);
  		if (IS_ERR(de)) {
  			erofs_err(sb, "fail to readdir of logical block %u of nid %llu",
-				  i, EROFS_I(dir)->nid);
+				  erofs_blknr(sb, dbstart), EROFS_I(dir)->nid);
  			err = PTR_ERR(de);
  			break;
  		}
@@ -79,25 +74,19 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
  			break;
  		}
  
-		maxsize = min_t(unsigned int, dirsize - ctx->pos + ofs, bsz);
-
+		maxsize = min_t(unsigned int, dir->i_size - dbstart, bsz);
  		/* search dirents at the arbitrary position */
  		if (initial) {
  			initial = false;
-
  			ofs = roundup(ofs, sizeof(struct erofs_dirent));
-			ctx->pos = erofs_pos(sb, i) + ofs;
-			if (ofs >= nameoff)
-				goto skip_this;
+			ctx->pos = dbstart + ofs;
  		}
  
  		err = erofs_fill_dentries(dir, ctx, de, (void *)de + ofs,
  					  nameoff, maxsize);
  		if (err)
  			break;
-skip_this:
-		ctx->pos = erofs_pos(sb, i) + maxsize;
-		++i;
+		ctx->pos = dbstart + maxsize;
  		ofs = 0;
  	}
  	erofs_put_metabuf(&buf);
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 736607675396..45dc15ebd870 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -220,7 +220,7 @@ struct erofs_buf {
  };
  #define __EROFS_BUF_INITIALIZER	((struct erofs_buf){ .page = NULL })
  
-#define erofs_blknr(sb, addr)	((addr) >> (sb)->s_blocksize_bits)
+#define erofs_blknr(sb, addr)	((erofs_blk_t)((addr) >> (sb)->s_blocksize_bits))
  #define erofs_blkoff(sb, addr)	((addr) & ((sb)->s_blocksize - 1))
  #define erofs_pos(sb, blk)	((erofs_off_t)(blk) << (sb)->s_blocksize_bits)
  #define erofs_iblks(i)	(round_up((i)->i_size, i_blocksize(i)) >> (i)->i_blkbits)
-- 2.43.5