Re: [PATCH v2] erofs-utils: lib: fix erofs_iterate_dir() recursion

[Gao Xiang <xiang@kernel.org>]

On Sat, Jul 22, 2023 at 03:04:23PM +0800, Jingbo Xu wrote:
> 
> 
> On 7/22/23 2:20 PM, Gao Xiang wrote:
> > Hi Jingbo,
> > 
> > On Sat, Jul 22, 2023 at 01:40:09PM +0800, Jingbo Xu wrote:
> >> ctx->dir may have changed when ctx is reused along erofs_iterate_dir()
> >> recursion.
> >>
> >> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> >> ---
> >> changes since last version:
> >> since traverse_dirents() can be called multiple times in one single
> >> erofs_iterate_dir() call, ctx->dir may have changed at the entry of
> >> traverse_dirents().  The previous v1 shall be deprecated.
> >>
> >> v1: https://lore.kernel.org/all/20230718052101.124039-3-jefflexu@linux.alibaba.com/
> > 
> > I plan to drop this commit directly.  `struct erofs_dir_context` is not
> > designed for reusing recursively. It's not the case just due to
> > `ctx->dir` but also internal states.
> > 
> > You need to build another ctx for recursion.
> 
> It seems that ctx is reused to avoid stack overflow.  So we have to
> allocate ctx on heap to avoid stack overflow?

It'd be better to use heap space for allocation in principle (even
avoid recursion), but I think it's just some userspace code and
stack space to enough in general.

Thanks,
Gao Xiang

> 
> -- 
> Thanks,
> Jingbo