On 2019-8-18 10:53, Matthew Wilcox wrote:
On Sun, Aug 18, 2019 at 10:32:45AM +0800, Gao Xiang wrote:
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?
I don't think it matters whether it's due to a disk error or a corrupted image. We can't read the directory entry, so we should probably return -EFSCORRUPTED. Thinking about it some more, read_mapping_page() can also return -ENOMEM, so it should probably look something like this:
err = 0; if (dentry_page == ERR_PTR(-ENOMEM)) err = -ENOMEM; else if (IS_ERR(dentry_page)) { errln("fail to readdir of logical block %u of nid %llu", i, EROFS_V(dir)->nid); err = -EFSCORRUPTED;
Well, if there is real IO error happen under filesystem, we should return -EIO instead of EFSCORRUPTED?
The right fix may be that doing sanity check on on-disk blkaddr, and return -EFSCORRUPTED if the blkaddr is invalid and propagate the error to its caller erofs_readdir(), IIUC below error info.
[36297.354090] attempt to access beyond end of device [36297.354098] loop17: rw=0, want=29887428984, limit=1953128 [36297.354107] attempt to access beyond end of device [36297.354109] loop17: rw=0, want=29887428480, limit=1953128 [36301.827234] attempt to access beyond end of device [36301.827243] loop17: rw=0, want=29887428480, limit=1953128
Thanks,
} if (err) break;