Re: [PATCH] Revert "bcache: fix improper use of bi_end_io"

[Christoph Hellwig <hch@infradead.org>]

On Tue, Jan 13, 2026 at 03:30:41AM -0500, Kent Overstreet wrote:
> On Tue, Jan 13, 2026 at 12:07:54AM -0800, Christoph Hellwig wrote:
> > On Tue, Jan 13, 2026 at 02:09:39PM +0800, colyli@fnnas.com wrote:
> > > From: Coly Li <colyli@fnnas.com>
> > > 
> > > This reverts commit 53280e398471f0bddbb17b798a63d41264651325.
> > > 
> > > The above commit tries to address the race in bio chain handling,
> > > but it seems in detached_dev_end_io() simply using bio_endio() to
> > > replace bio->bi_end_io() may introduce potential regression.
> > > 
> > > This patch revert the commit, let's wait for better fix from Shida.
> > 
> > That's a pretty vague commit message for reverting a clear API
> > violation that has caused trouble.  What is the story here?
> 
> Christoph, you can't call bio_endio() on the same bio twice. You should
> know this. Calling a bare bi_end_io function is the correct thing to do
> when we're getting called from bio_endio().

Hi Kent,

indeed, calling bio_endio() twice is a very bad idea.  Nothing in the
quoted commit log indicates that is the case, though.  If that is
the problem it needs to be fixed, but calling ->bi_end_io directly
is not the proper fix either.  That's eaxtly why I'm asking for the
story behind this.