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SubjectRe: [PATCH] erofs: update ctx->pos for every emitted dirent
Hi Hongnan,

On Fri, May 27, 2022 at 03:25:36PM +0800, 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 | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
> index 18e59821c597..3015974fe2ff 100644
> --- a/fs/erofs/dir.c
> +++ b/fs/erofs/dir.c
> @@ -22,11 +22,12 @@ 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, void *dentry_begin,
> unsigned int nameoff, unsigned int maxsize)
> {
> - struct erofs_dirent *de = dentry_blk + *ofs;
> + struct erofs_dirent *de = dentry_begin;
> const struct erofs_dirent *end = dentry_blk + nameoff;
> + loff_t begin_pos = ctx->pos;
>
> while (de < end) {
> const char *de_name;
> @@ -59,9 +60,9 @@ 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;
> + ctx->pos = begin_pos + maxsize;
> return 0;
> }
>
> @@ -110,11 +111,9 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
> goto skip_this;
> }
>
> - err = erofs_fill_dentries(dir, ctx, de, &ofs,
> + err = erofs_fill_dentries(dir, ctx, de, de + ofs,
> nameoff, maxsize);

This will break the calculation, since de is a pointer of erofs_dirent
rather than byte-based.

Thanks,
Gao Xiang

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