Re: [PATCH v2] staging: erofs: fix an error handling in erofs_readdir()

From: Gao Xiang
Date: Sat Aug 17 2019 - 22:33:12 EST

Hi Willy,

On Sat, Aug 17, 2019 at 07:20:55PM -0700, Matthew Wilcox wrote:
> On Sun, Aug 18, 2019 at 09:56:31AM +0800, Gao Xiang wrote:
> > @@ -82,8 +82,12 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
> > unsigned int nameoff, maxsize;
> >
> > dentry_page = read_mapping_page(mapping, i, NULL);
> > - if (IS_ERR(dentry_page))
> > - continue;
> > + if (IS_ERR(dentry_page)) {
> > + errln("fail to readdir of logical block %u of nid %llu",
> > + i, EROFS_V(dir)->nid);
> > + err = PTR_ERR(dentry_page);
> > + break;
> I don't think you want to use the errno that came back from
> read_mapping_page() (which is, I think, always going to be -EIO).
> Rather you want -EFSCORRUPTED, at least if I understand the recent
> patches to ext2/ext4/f2fs/xfs/...

Thanks for your reply and noticing this. :)

Yes, as I talked with you about read_mapping_page() in a xfs related
topic earlier, I think I fully understand what returns here.

I actually had some concern about that before sending out this patch.
You know the status is
PG_uptodate is not set and PG_error is set here.

But we cannot know it is actually a disk read error or due to
corrupted images (due to lack of page flags or some status, and
I think it could be a waste of page structure space for such
corrupted image or disk error)...

And some people also like propagate errors from insiders...
(and they could argue about err = -EFSCORRUPTED as well..)

I'd like hear your suggestion about this after my words above?
still return -EFSCORRUPTED?

Gao Xiang