Re: [PATCH] fs: buffer: check huge page size instead of single page for invalidatepage

[Yang Shi]

On Sun, Sep 19, 2021 at 7:41 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> On Fri, Sep 17, 2021 at 05:07:03PM -0700, Yang Shi wrote:
> > > The debugging showed the page passed to invalidatepage is a huge page
> > > and the length is the size of huge page instead of single page due to
> > > read only FS THP support.  But block_invalidatepage() would throw BUG if
> > > the size is greater than single page.
>
> Things have already gone wrong before we get to this point.  See
> do_dentry_open().  You aren't supposed to be able to get a writable file
> descriptor on a file which has had huge pages added to the page cache
> without the filesystem's knowledge.  That's the problem that needs to
> be fixed.

I don't quite understand your point here. Do you mean do_dentry_open()
should fail for such cases instead of truncating the page cache?