On Tue, Oct 18, 2022 at 01:48:34PM -0700, Andrew Morton wrote: > On Tue, 18 Oct 2022 15:39:39 +0100 Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > On Tue, Oct 18, 2022 at 10:36:39PM +0800, Tuo Cao wrote: > > > The folio returned from __filemap_get_folio may be a NULL, it will > > > causes the kernel crash when access folio->page. > > > > This is not a bug. &folio->page does not dereference folio but performs > > pointer arithmetic. > > This is the third attempt to "fix" this. So far. I think we should > take the hint and make the check for a null pointer more explicit. I think it's doing a great job of pointing out how many alleged kernel programmers don't actually understand C and aren't capable of searching mailing lists to see if somebody else already sent a patch. Hopefully somebody's keeping track and is feeding this information into their hiring algorithms. The real solution is to convert all the callers of pagecache_get_page() to use folios, and then we can delete this code. I have a small series in progress. The amount of text savings is immense; half a kilobyte from one conversion alone. Our compound_head() has got very bloated.
