Re: [PATCH v2] erofs: update ctx->pos for every emitted dirent

[Chao Yu <chao@kernel.org>]

On 2022/6/9 11:40, Hongnan Li wrote:
> erofs_readdir update ctx->pos after filling a batch of dentries
> and it may cause dir/files duplication for NFS readdirplus which
> depends on ctx->pos to fill dir correctly. So update ctx->pos for
> every emitted dirent in erofs_fill_dentries to fix it.
> 
> Fixes: 3e917cc305c6 ("erofs: make filesystem exportable")
> Signed-off-by: Hongnan Li <hongnan.li@linux.alibaba.com>
> ---
>   fs/erofs/dir.c | 20 ++++++++++----------
>   1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
> index 18e59821c597..94ef5287237a 100644
> --- a/fs/erofs/dir.c
> +++ b/fs/erofs/dir.c
> @@ -22,10 +22,9 @@ static void debug_one_dentry(unsigned char d_type, const char *de_name,
>   }
>   
>   static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
> -			       void *dentry_blk, unsigned int *ofs,
> +			       void *dentry_blk, struct erofs_dirent *de,
>   			       unsigned int nameoff, unsigned int maxsize)
>   {
> -	struct erofs_dirent *de = dentry_blk + *ofs;
>   	const struct erofs_dirent *end = dentry_blk + nameoff;
>   
>   	while (de < end) {
> @@ -59,9 +58,8 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
>   			/* stopped by some reason */
>   			return 1;
>   		++de;
> -		*ofs += sizeof(struct erofs_dirent);
> +		ctx->pos += sizeof(struct erofs_dirent);
>   	}
> -	*ofs = maxsize;
>   	return 0;
>   }
>   
> @@ -95,7 +93,7 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
>   				  "invalid de[0].nameoff %u @ nid %llu",
>   				  nameoff, EROFS_I(dir)->nid);
>   			err = -EFSCORRUPTED;
> -			goto skip_this;
> +			break;
>   		}
>   
>   		maxsize = min_t(unsigned int,
> @@ -106,17 +104,19 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
>   			initial = false;
>   
>   			ofs = roundup(ofs, sizeof(struct erofs_dirent));
> -			if (ofs >= nameoff)
> +			if (ofs >= nameoff) {
> +				ctx->pos = blknr_to_addr(i) + ofs;
>   				goto skip_this;
> +			}
>   		}
>   
> -		err = erofs_fill_dentries(dir, ctx, de, &ofs,
> -					  nameoff, maxsize);
> -skip_this:
>   		ctx->pos = blknr_to_addr(i) + ofs;

Why updating ctx->pos before erofs_fill_dentries()?

Thanks,

> -
> +		err = erofs_fill_dentries(dir, ctx, de, (void *)de + ofs,
> +					  nameoff, maxsize);
>   		if (err)
>   			break;
> +		ctx->pos = blknr_to_addr(i) + maxsize;
> +skip_this:
>   		++i;
>   		ofs = 0;
>   	}