linux-kernel - [PATCH 08/11] x86/mm/pat/32: Remove pgd

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Date:	Tue, 22 Sep 2015 08:23:38 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:	Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Brian Gerst <brgerst@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Waiman Long <waiman.long@...com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 08/11] x86/mm/pat/32: Remove pgd_list use from the PAT code

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@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Waiman Long <Waiman.Long@...com>
Cc: linux-mm@...ck.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/mm/pageattr.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index b784ed7c9a7e..bc7533801014 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -12,6 +12,7 @@
 #include <linux/pfn.h>
 #include <linux/percpu.h>
 #include <linux/gfp.h>
+#include <linux/oom.h>
 #include <linux/pci.h>
 #include <linux/vmalloc.h>
 
@@ -438,18 +439,36 @@ 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;
 
-		list_for_each_entry(page, &pgd_list, lru) {
+		rcu_read_lock(); /* Task list walk */
+
+		for_each_process(g) {
+			struct task_struct *p;
+			struct mm_struct *mm;
+			spinlock_t *pgt_lock;
 			pgd_t *pgd;
 			pud_t *pud;
 			pmd_t *pmd;
 
-			pgd = (pgd_t *)page_address(page) + pgd_index(address);
+			p = find_lock_task_mm(g);
+			if (!p)
+				continue;
+
+			mm = p->mm;
+			pgt_lock = &mm->page_table_lock;
+			spin_lock(pgt_lock);
+
+			pgd = 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);
+
+			task_unlock(p);
 		}
+		rcu_read_unlock();
 	}
 #endif
 }
-- 
2.1.4

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