linux-kernel - [PATCH 08/12] x86/mm: Remove pgd_list use from vmalloc_sync

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Date:	Thu, 11 Jun 2015 16:07:13 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	linux-kernel@...r.kernel.org
Cc:	linux-mml@...r.kernel.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 08/12] x86/mm: Remove pgd_list use from vmalloc_sync_all()

The vmalloc() code uses vmalloc_sync_all() to synchronize changes to
the global reference kernel PGD to task PGDs.

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

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: 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@...r.kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/mm/fault.c   | 21 ++++++++++++++-------
 arch/x86/mm/init_64.c |  3 ++-
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 50342825f221..2d587e548b59 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -235,24 +235,31 @@ void vmalloc_sync_all(void)
 	for (address = VMALLOC_START & PMD_MASK;
 	     address >= TASK_SIZE && address < FIXADDR_TOP;
 	     address += PMD_SIZE) {
-		struct page *page;
 
+		struct task_struct *g, *p;
+
+		rcu_read_lock();
 		spin_lock(&pgd_lock);
-		list_for_each_entry(page, &pgd_list, lru) {
+
+		for_each_process_thread(g, p) {
 			spinlock_t *pgt_lock;
-			pmd_t *ret;
+			pmd_t *pmd_ret;
 
-			/* 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 on Xen: */
+			pgt_lock = &p->mm->page_table_lock;
 			spin_lock(pgt_lock);
-			ret = vmalloc_sync_one(page_address(page), address);
+			pmd_ret = vmalloc_sync_one(p->mm->pgd, address);
 			spin_unlock(pgt_lock);
 
-			if (!ret)
+			if (!pmd_ret)
 				break;
 		}
+
 		spin_unlock(&pgd_lock);
+		rcu_read_unlock();
 	}
 }
 
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index beee532b76a7..730560c4873e 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -184,11 +184,12 @@ void sync_global_pgds(unsigned long start, unsigned long end)
 		spin_lock(&pgd_lock);
 
 		for_each_process_thread(g, p) {
-			pgd_t *pgd = p->mm->pgd;
+			pgd_t *pgd;
 			spinlock_t *pgt_lock;
 
 			if (!p->mm)
 				continue;
+			pgd = p->mm->pgd;
 
 			/* The pgt_lock is only used by Xen: */
 			pgt_lock = &p->mm->page_table_lock;
-- 
2.1.4

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