Re: question about mapping_set_error when writeback fails?

[Matthew Wilcox <willy@infradead.org>]

On Wed, Jun 02, 2021 at 01:27:56PM -0700, Darrick J. Wong wrote:
> In iomap_finish_page_writeback,
> 
> static void
> iomap_finish_page_writeback(struct inode *inode, struct page *page,
> 		int error, unsigned int len)
> {
> 	struct iomap_page *iop = to_iomap_page(page);
> 
> 	if (error) {
> 		SetPageError(page);
> 		mapping_set_error(inode->i_mapping, -EIO);
> 
> Why don't we pass error to mapping_set_error here?  If the writeback
> completion failed due to insufficient space (e.g. extent mapping btree
> expansion hit ENOSPC while trying to perform an unwritten extent
> conversion) then we set AS_EIO which causes fsync to return EIO instead
> of ENOSPC like you'd expect.

Hah, I noticed the same thing a few weeks ago and didn't get round to
asking about it yet.  I'm pretty sure we should pass the real error to
mapping_set_error().

I also wonder if we shouldn't support more of the errors from
blk_errors, like -ETIMEDOUT or -EILSEQ, but that's a different
conversation.