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mm: introduce do_shared_fault() and drop do_fault()
Introduce do_shared_fault(). The function does what do_fault() does for write faults to shared mappings Unlike do_fault(), do_shared_fault() is relatively clean and straight-forward. Old do_fault() is not needed anymore. Let it die. [lliubbo@gmail.com: fix NULL pointer dereference] Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Rik van Riel <riel@redhat.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Matthew Wilcox <matthew.r.wilcox@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Bob Liu <bob.liu@oracle.com> Cc: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov
Linus Torvalds
parent
ec47c3b954
commit
f0c6d4d295
230
mm/memory.c
230
mm/memory.c
@ -2748,7 +2748,7 @@ reuse:
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* bit after it clear all dirty ptes, but before a racing
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* do_wp_page installs a dirty pte.
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*
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* do_fault is protected similarly.
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* do_shared_fault is protected similarly.
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*/
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if (!page_mkwrite) {
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wait_on_page_locked(dirty_page);
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@ -3410,188 +3410,86 @@ uncharge_out:
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return ret;
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}
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/*
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* do_fault() tries to create a new page mapping. It aggressively
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* tries to share with existing pages, but makes a separate copy if
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* the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
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* the next page fault.
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*
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* As this is called only for pages that do not currently exist, we
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* do not need to flush old virtual caches or the TLB.
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*
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* We enter with non-exclusive mmap_sem (to exclude vma changes,
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* but allow concurrent faults), and pte neither mapped nor locked.
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* We return with mmap_sem still held, but pte unmapped and unlocked.
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*/
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static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
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static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
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unsigned long address, pmd_t *pmd,
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pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
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{
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pte_t *page_table;
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struct page *fault_page;
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struct address_space *mapping;
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spinlock_t *ptl;
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struct page *page, *fault_page;
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struct page *cow_page;
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pte_t entry;
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int anon = 0;
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struct page *dirty_page = NULL;
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int ret;
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int page_mkwrite = 0;
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/*
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* If we do COW later, allocate page befor taking lock_page()
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* on the file cache page. This will reduce lock holding time.
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*/
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if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
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if (unlikely(anon_vma_prepare(vma)))
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return VM_FAULT_OOM;
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cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
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if (!cow_page)
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return VM_FAULT_OOM;
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if (mem_cgroup_newpage_charge(cow_page, mm, GFP_KERNEL)) {
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page_cache_release(cow_page);
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return VM_FAULT_OOM;
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}
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} else
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cow_page = NULL;
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pte_t entry, *pte;
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int dirtied = 0;
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struct vm_fault vmf;
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int ret, tmp;
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ret = __do_fault(vma, address, pgoff, flags, &fault_page);
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if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
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goto uncharge_out;
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return ret;
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/*
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* Should we do an early C-O-W break?
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* Check if the backing address space wants to know that the page is
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* about to become writable
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*/
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page = fault_page;
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if (flags & FAULT_FLAG_WRITE) {
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if (!(vma->vm_flags & VM_SHARED)) {
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page = cow_page;
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anon = 1;
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copy_user_highpage(page, fault_page, address, vma);
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__SetPageUptodate(page);
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} else {
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/*
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* If the page will be shareable, see if the backing
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* address space wants to know that the page is about
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* to become writable
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*/
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if (vma->vm_ops->page_mkwrite) {
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struct vm_fault vmf;
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int tmp;
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if (!vma->vm_ops->page_mkwrite)
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goto set_pte;
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vmf.virtual_address =
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(void __user *)(address & PAGE_MASK);
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vmf.pgoff = pgoff;
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vmf.flags = flags;
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vmf.page = fault_page;
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unlock_page(page);
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vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
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tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
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if (unlikely(tmp &
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(VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
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ret = tmp;
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goto unwritable_page;
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}
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if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
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lock_page(page);
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if (!page->mapping) {
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ret = 0; /* retry the fault */
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unlock_page(page);
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goto unwritable_page;
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}
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} else
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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page_mkwrite = 1;
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}
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}
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unlock_page(fault_page);
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vmf.virtual_address = (void __user *)(address & PAGE_MASK);
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vmf.pgoff = pgoff;
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vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
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vmf.page = fault_page;
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tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
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if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
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page_cache_release(fault_page);
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return tmp;
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}
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page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
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/*
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* This silly early PAGE_DIRTY setting removes a race
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* due to the bad i386 page protection. But it's valid
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* for other architectures too.
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*
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* Note that if FAULT_FLAG_WRITE is set, we either now have
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* an exclusive copy of the page, or this is a shared mapping,
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* so we can make it writable and dirty to avoid having to
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* handle that later.
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*/
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/* Only go through if we didn't race with anybody else... */
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if (likely(pte_same(*page_table, orig_pte))) {
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flush_icache_page(vma, page);
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entry = mk_pte(page, vma->vm_page_prot);
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if (flags & FAULT_FLAG_WRITE)
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entry = maybe_mkwrite(pte_mkdirty(entry), vma);
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else if (pte_file(orig_pte) && pte_file_soft_dirty(orig_pte))
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pte_mksoft_dirty(entry);
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if (anon) {
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inc_mm_counter_fast(mm, MM_ANONPAGES);
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page_add_new_anon_rmap(page, vma, address);
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} else {
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inc_mm_counter_fast(mm, MM_FILEPAGES);
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page_add_file_rmap(page);
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if (flags & FAULT_FLAG_WRITE) {
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dirty_page = page;
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get_page(dirty_page);
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}
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}
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set_pte_at(mm, address, page_table, entry);
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/* no need to invalidate: a not-present page won't be cached */
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update_mmu_cache(vma, address, page_table);
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} else {
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if (cow_page)
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mem_cgroup_uncharge_page(cow_page);
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if (anon)
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page_cache_release(page);
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else
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anon = 1; /* no anon but release faulted_page */
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}
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pte_unmap_unlock(page_table, ptl);
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if (dirty_page) {
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struct address_space *mapping = page->mapping;
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int dirtied = 0;
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if (set_page_dirty(dirty_page))
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dirtied = 1;
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unlock_page(dirty_page);
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put_page(dirty_page);
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if ((dirtied || page_mkwrite) && mapping) {
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/*
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* Some device drivers do not set page.mapping but still
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* dirty their pages
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*/
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balance_dirty_pages_ratelimited(mapping);
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}
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/* file_update_time outside page_lock */
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if (vma->vm_file && !page_mkwrite)
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file_update_time(vma->vm_file);
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} else {
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unlock_page(fault_page);
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if (anon)
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if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
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lock_page(fault_page);
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if (!fault_page->mapping) {
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unlock_page(fault_page);
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page_cache_release(fault_page);
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return 0; /* retry */
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}
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} else
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VM_BUG_ON_PAGE(!PageLocked(fault_page), fault_page);
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set_pte:
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pte = pte_offset_map_lock(mm, pmd, address, &ptl);
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if (unlikely(!pte_same(*pte, orig_pte))) {
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pte_unmap_unlock(pte, ptl);
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unlock_page(fault_page);
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page_cache_release(fault_page);
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return ret;
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}
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return ret;
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flush_icache_page(vma, fault_page);
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entry = mk_pte(fault_page, vma->vm_page_prot);
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entry = maybe_mkwrite(pte_mkdirty(entry), vma);
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inc_mm_counter_fast(mm, MM_FILEPAGES);
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page_add_file_rmap(fault_page);
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set_pte_at(mm, address, pte, entry);
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unwritable_page:
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page_cache_release(page);
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return ret;
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uncharge_out:
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/* fs's fault handler get error */
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if (cow_page) {
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mem_cgroup_uncharge_page(cow_page);
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page_cache_release(cow_page);
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/* no need to invalidate: a not-present page won't be cached */
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update_mmu_cache(vma, address, pte);
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pte_unmap_unlock(pte, ptl);
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if (set_page_dirty(fault_page))
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dirtied = 1;
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mapping = fault_page->mapping;
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unlock_page(fault_page);
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if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) {
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/*
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* Some device drivers do not set page.mapping but still
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* dirty their pages
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*/
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balance_dirty_pages_ratelimited(mapping);
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}
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/* file_update_time outside page_lock */
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if (vma->vm_file && !vma->vm_ops->page_mkwrite)
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file_update_time(vma->vm_file);
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return ret;
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}
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@ -3609,7 +3507,7 @@ static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
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if (!(vma->vm_flags & VM_SHARED))
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return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
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orig_pte);
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return do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
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return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
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}
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/*
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@ -3647,7 +3545,7 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
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if (!(vma->vm_flags & VM_SHARED))
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return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
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orig_pte);
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return do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
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return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
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}
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static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
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