The vmalloc() code uses vmalloc_sync_all() to synchronize changes to
the global reference kernel PGD to task PGDs in certain rare cases,
like register_die_notifier().
This use seems to be somewhat questionable, as most other vmalloc
page table fixups are vmalloc_fault() driven, but nevertheless
it's there and it's using the pgd_list.
But we don't need the global list, as we can walk the task list
under RCU.
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: Oleg Nesterov <oleg@xxxxxxxxxx>
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@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/mm/fault.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 deletions(-)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 50342825f221..366b8232f4b3 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -235,23 +235,35 @@ void vmalloc_sync_all(void)
for (address = VMALLOC_START & PMD_MASK;
address >= TASK_SIZE && address < FIXADDR_TOP;
address += PMD_SIZE) {
- struct page *page;
- spin_lock(&pgd_lock);
- list_for_each_entry(page, &pgd_list, lru) {
+ struct task_struct *g, *p;
+
+ spin_lock(&pgd_lock); /* Implies rcu_read_lock(): */
+
+ for_each_process_thread(g, p) {
+ struct mm_struct *mm;
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;
+ task_lock(p);
+ mm = p->mm;
+ if (!mm) {
+ task_unlock(p);
+ continue;
+ }
+ /* The pgt_lock is only used on Xen: */
+ pgt_lock = &mm->page_table_lock;
spin_lock(pgt_lock);
- ret = vmalloc_sync_one(page_address(page), address);
+ pmd_ret = vmalloc_sync_one(mm->pgd, address);
spin_unlock(pgt_lock);
- if (!ret)
+ task_unlock(p);
+
+ if (!pmd_ret)
break;
}
+
spin_unlock(&pgd_lock);
}
}
--
2.1.4
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