#include <linux/freezer.h>
#include <linux/oom.h>
#include <linux/numa.h>
+#include <linux/pagewalk.h>
#include <asm/tlbflush.h>
#include "internal.h"
return atomic_read(&mm->mm_users) == 0;
}
+static int break_ksm_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long next,
+ struct mm_walk *walk)
+{
+ struct page *page = NULL;
+ spinlock_t *ptl;
+ pte_t *pte;
+ int ret;
+
+ if (pmd_leaf(*pmd) || !pmd_present(*pmd))
+ return 0;
+
+ pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+ if (pte_present(*pte)) {
+ page = vm_normal_page(walk->vma, addr, *pte);
+ } else if (!pte_none(*pte)) {
+ swp_entry_t entry = pte_to_swp_entry(*pte);
+
+ /*
+ * As KSM pages remain KSM pages until freed, no need to wait
+ * here for migration to end.
+ */
+ if (is_migration_entry(entry))
+ page = pfn_swap_entry_to_page(entry);
+ }
+ ret = page && PageKsm(page);
+ pte_unmap_unlock(pte, ptl);
+ return ret;
+}
+
+static const struct mm_walk_ops break_ksm_ops = {
+ .pmd_entry = break_ksm_pmd_entry,
+};
+
/*
- * We use break_ksm to break COW on a ksm page: it's a stripped down
- *
- * if (get_user_pages(addr, 1, FOLL_WRITE, &page, NULL) == 1)
- * put_page(page);
+ * We use break_ksm to break COW on a ksm page by triggering unsharing,
+ * such that the ksm page will get replaced by an exclusive anonymous page.
*
- * but taking great care only to touch a ksm page, in a VM_MERGEABLE vma,
+ * We take great care only to touch a ksm page, in a VM_MERGEABLE vma,
* in case the application has unmapped and remapped mm,addr meanwhile.
* Could a ksm page appear anywhere else? Actually yes, in a VM_PFNMAP
* mmap of /dev/mem, where we would not want to touch it.
*
- * FAULT_FLAG/FOLL_REMOTE are because we do this outside the context
+ * FAULT_FLAG_REMOTE/FOLL_REMOTE are because we do this outside the context
* of the process that owns 'vma'. We also do not want to enforce
* protection keys here anyway.
*/
static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
{
- struct page *page;
vm_fault_t ret = 0;
do {
- bool ksm_page = false;
+ int ksm_page;
cond_resched();
- page = follow_page(vma, addr,
- FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE);
- if (IS_ERR_OR_NULL(page))
- break;
- if (PageKsm(page))
- ksm_page = true;
- put_page(page);
-
+ ksm_page = walk_page_range_vma(vma, addr, addr + 1,
+ &break_ksm_ops, NULL);
+ if (WARN_ON_ONCE(ksm_page < 0))
+ return ksm_page;
if (!ksm_page)
return 0;
ret = handle_mm_fault(vma, addr,
- FAULT_FLAG_WRITE | FAULT_FLAG_REMOTE,
+ FAULT_FLAG_UNSHARE | FAULT_FLAG_REMOTE,
NULL);
} while (!(ret & (VM_FAULT_SIGBUS | VM_FAULT_SIGSEGV | VM_FAULT_OOM)));
/*