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SubjectRe: [PATCH 02/12] x86/mm/hotplug: Remove pgd_list use from the memory hotplug code

* Waiman Long <waiman.long@hp.com> wrote:

> >@@ -169,29 +169,33 @@ void sync_global_pgds(unsigned long start, unsigned long end, int removed)
> >
> > for (address = start; address<= end; address += PGDIR_SIZE) {
> > const pgd_t *pgd_ref = pgd_offset_k(address);
> >- struct page *page;
> >+ struct task_struct *g, *p;
> >
> > /*
> >- * When it is called after memory hot remove, pgd_none()
> >- * returns true. In this case (removed == 1), we must clear
> >- * the PGD entries in the local PGD level page.
> >+ * When this function is called after memory hot remove,
> >+ * pgd_none() already returns true, but only the reference
> >+ * kernel PGD has been cleared, not the process PGDs.
> >+ *
> >+ * So clear the affected entries in every process PGD as well:
> > */
> > if (pgd_none(*pgd_ref)&& !removed)
> > continue;
> >
> > spin_lock(&pgd_lock);
> >- list_for_each_entry(page,&pgd_list, lru) {
> >- pgd_t *pgd;
> >+
> >+ for_each_process_thread(g, p) {
> >+ pgd_t *pgd = p->mm->pgd;
> > spinlock_t *pgt_lock;
> >
> >- pgd = (pgd_t *)page_address(page) + pgd_index(address);
> >- /* the pgt_lock only for Xen */
> >- pgt_lock =&pgd_page_get_mm(page)->page_table_lock;
> >+ if (!p->mm)
> >+ continue;
>
> pgd was initialized to p->mm->pgd before the "p->mm" check is done.
> Shouldn't the initialization be moved after that.

Yes, already found this bug in testing and fixed it - will send out a new series
with all the feedback so far addressed.

Thanks,

Ingo


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