f2fs: fix readdir incorrectness

In the previous Al Viro's readdir patch set, there occurs a bug when
running
xfstest: 006 as follows.

[Error output]
alpha size = 4, name length = 6, total files = 4096, nproc=1
1023 files created
rm: cannot remove `/mnt/f2fs/permname.15150/a': Directory not empty

[Correct output]
alpha size = 4, name length = 6, total files = 4096, nproc=1
4097 files created

This bug is due to the misupdate of directory position in ctx.
So, this patch fixes this.

[AV: fixed a braino]

CC: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/f2fs/dir.c

@@ -610,13 +610,12 @@ static int f2fs_readdir(struct file *file, struct dir_context *ctx)
 {
 	struct inode *inode = file_inode(file);
 	unsigned long npages = dir_blocks(inode);
-	unsigned int bit_pos = 0, start_bit_pos = 0;
+	unsigned int bit_pos = 0;
 	struct f2fs_dentry_block *dentry_blk = NULL;
 	struct f2fs_dir_entry *de = NULL;
 	struct page *dentry_page = NULL;
 	unsigned int n = ((unsigned long)ctx->pos / NR_DENTRY_IN_BLOCK);
 	unsigned char d_type = DT_UNKNOWN;
-	int slots;
 
 	bit_pos = ((unsigned long)ctx->pos % NR_DENTRY_IN_BLOCK);
 
@@ -625,7 +624,6 @@ static int f2fs_readdir(struct file *file, struct dir_context *ctx)
 		if (IS_ERR(dentry_page))
 			continue;
 
-		start_bit_pos = bit_pos;
 		dentry_blk = kmap(dentry_page);
 		while (bit_pos < NR_DENTRY_IN_BLOCK) {
 			bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
@@ -634,27 +632,27 @@ static int f2fs_readdir(struct file *file, struct dir_context *ctx)
 			if (bit_pos >= NR_DENTRY_IN_BLOCK)
 				break;
 
-			ctx->pos += bit_pos - start_bit_pos;
 			de = &dentry_blk->dentry[bit_pos];
 			if (de->file_type < F2FS_FT_MAX)
 				d_type = f2fs_filetype_table[de->file_type];
 			else
 				d_type = DT_UNKNOWN;
 			if (!dir_emit(ctx,
-				      dentry_blk->filename[bit_pos],
-				      le16_to_cpu(de->name_len),
-				      le32_to_cpu(de->ino), d_type))
-				goto success;
-			slots = GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
-			bit_pos += slots;
+					dentry_blk->filename[bit_pos],
+					le16_to_cpu(de->name_len),
+					le32_to_cpu(de->ino), d_type))
+				goto stop;
+
+			bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
+			ctx->pos = n * NR_DENTRY_IN_BLOCK + bit_pos;
 		}
 		bit_pos = 0;
 		ctx->pos = (n + 1) * NR_DENTRY_IN_BLOCK;
 		kunmap(dentry_page);
 		f2fs_put_page(dentry_page, 1);
 		dentry_page = NULL;
 	}
-success:
+stop:
 	if (dentry_page && !IS_ERR(dentry_page)) {
 		kunmap(dentry_page);
 		f2fs_put_page(dentry_page, 1);