The memory hotplug code uses sync_global_pgds() to synchronize updates
to the global (&init_mm) kernel PGD and the task PGDs. It does this
by iterating over the pgd_list - which list closely tracks task
creation/destruction via fork/clone.
But we want to remove this list, so that it does not have to be
maintained from fork()/exit(), so convert the memory hotplug code
to use the task list to iterate over all pgds in the system.
Also improve the comments a bit, to make this function easier
to understand.
Only lightly tested, as I don't have a memory hotplug setup.
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Andy Lutomirski <l...@amacapital.net>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Brian Gerst <brge...@gmail.com>
Cc: Denys Vlasenko <dvlas...@redhat.com>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Waiman Long <waiman.l...@hp.com>
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
arch/x86/mm/init_64.c | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 3fba623e3ba5..1921acbd49fd 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -160,8 +160,8 @@ static int __init nonx32_setup(char *str)
__setup("noexec32=", nonx32_setup);
/*
- * When memory was added/removed make sure all the processes MM have
- * suitable PGD entries in the local PGD level page.
+ * When memory was added/removed make sure all the process MMs have
+ * matching PGD entries in the local PGD level page as well.
*/
void sync_global_pgds(unsigned long start, unsigned long end, int removed)
{
@@ -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;
+
+ /* The pgt_lock is only used by Xen: */
+ pgt_lock = &p->mm->page_table_lock;
spin_lock(pgt_lock);
if (!pgd_none(*pgd_ref) && !pgd_none(*pgd))
- BUG_ON(pgd_page_vaddr(*pgd)
- != pgd_page_vaddr(*pgd_ref));
+ BUG_ON(pgd_page_vaddr(*pgd) !=
pgd_page_vaddr(*pgd_ref));
if (removed) {
if (pgd_none(*pgd_ref) && !pgd_none(*pgd))
--
2.1.4
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