linux-kernel - [PATCH 09/12] x86/mm/pat/32: Remove pgd

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Message-Id: <1434188955-31397-10-git-send-email-mingo@kernel.org>
Date:	Sat, 13 Jun 2015 11:49:12 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org, 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>,
	Thomas Gleixner <tglx@...utronix.de>,
	Waiman Long <Waiman.Long@...com>
Subject: [PATCH 09/12] 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 | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 997fc97e9072..4ff6a1808f1d 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -438,17 +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) {
+		/* We are holding pgd_lock, which implies rcu_read_lock(): */
+
+		for_each_process_thread(g, 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);
-			pud = pud_offset(pgd, address);
-			pmd = pmd_offset(pud, address);
-			set_pte_atomic((pte_t *)pmd, pte);
+			task_lock(p);
+			mm = p->mm;
+			if (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);
 		}
 	}
 #endif
-- 
2.1.4

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