linux-kernel - Re: [PATCH v2] staging: erofs: fix an error handling in erofs

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Message-ID: <20190818023240.GA7739@hsiangkao-HP-ZHAN-66-Pro-G1>
Date:   Sun, 18 Aug 2019 10:32:45 +0800
From:   Gao Xiang <hsiangkao@....com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Chao Yu <yuchao0@...wei.com>, Richard Weinberger <richard@....at>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org, linux-fsdevel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        linux-erofs@...ts.ozlabs.org, Chao Yu <chao@...nel.org>,
        Miao Xie <miaoxie@...wei.com>, Fang Wei <fangwei1@...wei.com>,
        Gao Xiang <gaoxiang25@...wei.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2] staging: erofs: fix an error handling in
 erofs_readdir()

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?

Thanks,
Gao Xiang