[PATCH 09/12] x86/mm/pat/32: Remove pgd_list use from the PAT code

[Ingo Molnar]

The 32-bit x86 PAT code uses __set_pmd_pte() to update pmds.

This uses pgd_list currently, but we don't need the global
list as we can walk the task list under RCU.

(This code already holds the pgd_lock.)

Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Waiman Long <Waiman.Long@xxxxxx>
Cc: linux-mm@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/mm/pageattr.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 997fc97e9072..93c134fdb398 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -438,18 +438,31 @@ static void __set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte)
 	set_pte_atomic(kpte, pte);
 #ifdef CONFIG_X86_32
 	if (!SHARED_KERNEL_PMD) {
-		struct page *page;
+		struct task_struct *g, *p;
 
-		list_for_each_entry(page, &pgd_list, lru) {
+		rcu_read_lock();
+
+		for_each_process_thread(g, p) {
+			spinlock_t *pgt_lock;
 			pgd_t *pgd;
 			pud_t *pud;
 			pmd_t *pmd;
 
-			pgd = (pgd_t *)page_address(page) + pgd_index(address);
+			if (!p->mm)
+				continue;
+
+			pgt_lock = &p->mm->page_table_lock;
+			spin_lock(pgt_lock);
+
+			pgd = p->mm->pgd + pgd_index(address);
 			pud = pud_offset(pgd, address);
 			pmd = pmd_offset(pud, address);
 			set_pte_atomic((pte_t *)pmd, pte);
+
+			spin_unlock(pgt_lock);
 		}
+
+		rcu_read_unlock();
 	}
 #endif
 }
-- 
2.1.4

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