[RFC] Missing compound_head() in memory-failure

[Matthew Wilcox <willy@xxxxxxxxxxxxx>]

Unless I am mistaken, you have to pass the compound head of the page
which has the error to collect_procs().  Am I mistaken?

(found by code inspection as part of the folio work; I think
collect_procs() needs to take a folio, which would eliminate this class
of errors)

+++ b/mm/memory-failure.c
@@ -1633,7 +1633,7 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
         * SIGBUS (i.e. MF_MUST_KILL)
         */
        flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
-       collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);
+       collect_procs(compound_head(page), &tokill, flags & MF_ACTION_REQUIRED);

        list_for_each_entry(tk, &tokill, nd)
                if (tk->size_shift)