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>
diff --git a/mm/memory.c b/mm/memory.c
index 5be13e7..d4320e4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2748,7 +2748,7 @@
* bit after it clear all dirty ptes, but before a racing
* do_wp_page installs a dirty pte.
*
- * do_fault is protected similarly.
+ * do_shared_fault is protected similarly.
*/
if (!page_mkwrite) {
wait_on_page_locked(dirty_page);
@@ -3410,188 +3410,86 @@
return ret;
}
-/*
- * do_fault() tries to create a new page mapping. It aggressively
- * tries to share with existing pages, but makes a separate copy if
- * the FAULT_FLAG_WRITE is set in the flags parameter in order to avoid
- * the next page fault.
- *
- * As this is called only for pages that do not currently exist, we
- * do not need to flush old virtual caches or the TLB.
- *
- * We enter with non-exclusive mmap_sem (to exclude vma changes,
- * but allow concurrent faults), and pte neither mapped nor locked.
- * We return with mmap_sem still held, but pte unmapped and unlocked.
- */
-static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd,
pgoff_t pgoff, unsigned int flags, pte_t orig_pte)
{
- pte_t *page_table;
+ struct page *fault_page;
+ struct address_space *mapping;
spinlock_t *ptl;
- struct page *page, *fault_page;
- struct page *cow_page;
- pte_t entry;
- int anon = 0;
- struct page *dirty_page = NULL;
- int ret;
- int page_mkwrite = 0;
-
- /*
- * If we do COW later, allocate page befor taking lock_page()
- * on the file cache page. This will reduce lock holding time.
- */
- if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
-
- if (unlikely(anon_vma_prepare(vma)))
- return VM_FAULT_OOM;
-
- cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
- if (!cow_page)
- return VM_FAULT_OOM;
-
- if (mem_cgroup_newpage_charge(cow_page, mm, GFP_KERNEL)) {
- page_cache_release(cow_page);
- return VM_FAULT_OOM;
- }
- } else
- cow_page = NULL;
+ pte_t entry, *pte;
+ int dirtied = 0;
+ struct vm_fault vmf;
+ int ret, tmp;
ret = __do_fault(vma, address, pgoff, flags, &fault_page);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
- goto uncharge_out;
+ return ret;
/*
- * Should we do an early C-O-W break?
+ * Check if the backing address space wants to know that the page is
+ * about to become writable
*/
- page = fault_page;
- if (flags & FAULT_FLAG_WRITE) {
- if (!(vma->vm_flags & VM_SHARED)) {
- page = cow_page;
- anon = 1;
- copy_user_highpage(page, fault_page, address, vma);
- __SetPageUptodate(page);
- } else {
- /*
- * If the page will be shareable, see if the backing
- * address space wants to know that the page is about
- * to become writable
- */
- if (vma->vm_ops->page_mkwrite) {
- struct vm_fault vmf;
- int tmp;
+ if (!vma->vm_ops->page_mkwrite)
+ goto set_pte;
- vmf.virtual_address =
- (void __user *)(address & PAGE_MASK);
- vmf.pgoff = pgoff;
- vmf.flags = flags;
- vmf.page = fault_page;
+ unlock_page(fault_page);
+ vmf.virtual_address = (void __user *)(address & PAGE_MASK);
+ vmf.pgoff = pgoff;
+ vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
+ vmf.page = fault_page;
- unlock_page(page);
- vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
- tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
- if (unlikely(tmp &
- (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
- ret = tmp;
- goto unwritable_page;
- }
- if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
- lock_page(page);
- if (!page->mapping) {
- ret = 0; /* retry the fault */
- unlock_page(page);
- goto unwritable_page;
- }
- } else
- VM_BUG_ON_PAGE(!PageLocked(page), page);
- page_mkwrite = 1;
- }
- }
-
+ tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
+ if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
+ page_cache_release(fault_page);
+ return tmp;
}
- page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
-
- /*
- * This silly early PAGE_DIRTY setting removes a race
- * due to the bad i386 page protection. But it's valid
- * for other architectures too.
- *
- * Note that if FAULT_FLAG_WRITE is set, we either now have
- * an exclusive copy of the page, or this is a shared mapping,
- * so we can make it writable and dirty to avoid having to
- * handle that later.
- */
- /* Only go through if we didn't race with anybody else... */
- if (likely(pte_same(*page_table, orig_pte))) {
- flush_icache_page(vma, page);
- entry = mk_pte(page, vma->vm_page_prot);
- if (flags & FAULT_FLAG_WRITE)
- entry = maybe_mkwrite(pte_mkdirty(entry), vma);
- else if (pte_file(orig_pte) && pte_file_soft_dirty(orig_pte))
- pte_mksoft_dirty(entry);
- if (anon) {
- inc_mm_counter_fast(mm, MM_ANONPAGES);
- page_add_new_anon_rmap(page, vma, address);
- } else {
- inc_mm_counter_fast(mm, MM_FILEPAGES);
- page_add_file_rmap(page);
- if (flags & FAULT_FLAG_WRITE) {
- dirty_page = page;
- get_page(dirty_page);
- }
- }
- set_pte_at(mm, address, page_table, entry);
-
- /* no need to invalidate: a not-present page won't be cached */
- update_mmu_cache(vma, address, page_table);
- } else {
- if (cow_page)
- mem_cgroup_uncharge_page(cow_page);
- if (anon)
- page_cache_release(page);
- else
- anon = 1; /* no anon but release faulted_page */
- }
-
- pte_unmap_unlock(page_table, ptl);
-
- if (dirty_page) {
- struct address_space *mapping = page->mapping;
- int dirtied = 0;
-
- if (set_page_dirty(dirty_page))
- dirtied = 1;
- unlock_page(dirty_page);
- put_page(dirty_page);
- if ((dirtied || page_mkwrite) && mapping) {
- /*
- * Some device drivers do not set page.mapping but still
- * dirty their pages
- */
- balance_dirty_pages_ratelimited(mapping);
- }
-
- /* file_update_time outside page_lock */
- if (vma->vm_file && !page_mkwrite)
- file_update_time(vma->vm_file);
- } else {
- unlock_page(fault_page);
- if (anon)
+ if (unlikely(!(tmp & VM_FAULT_LOCKED))) {
+ lock_page(fault_page);
+ if (!fault_page->mapping) {
+ unlock_page(fault_page);
page_cache_release(fault_page);
+ return 0; /* retry */
+ }
+ } else
+ VM_BUG_ON_PAGE(!PageLocked(fault_page), fault_page);
+set_pte:
+ pte = pte_offset_map_lock(mm, pmd, address, &ptl);
+ if (unlikely(!pte_same(*pte, orig_pte))) {
+ pte_unmap_unlock(pte, ptl);
+ unlock_page(fault_page);
+ page_cache_release(fault_page);
+ return ret;
}
- return ret;
+ flush_icache_page(vma, fault_page);
+ entry = mk_pte(fault_page, vma->vm_page_prot);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ inc_mm_counter_fast(mm, MM_FILEPAGES);
+ page_add_file_rmap(fault_page);
+ set_pte_at(mm, address, pte, entry);
-unwritable_page:
- page_cache_release(page);
- return ret;
-uncharge_out:
- /* fs's fault handler get error */
- if (cow_page) {
- mem_cgroup_uncharge_page(cow_page);
- page_cache_release(cow_page);
+ /* no need to invalidate: a not-present page won't be cached */
+ update_mmu_cache(vma, address, pte);
+ pte_unmap_unlock(pte, ptl);
+
+ if (set_page_dirty(fault_page))
+ dirtied = 1;
+ mapping = fault_page->mapping;
+ unlock_page(fault_page);
+ if ((dirtied || vma->vm_ops->page_mkwrite) && mapping) {
+ /*
+ * Some device drivers do not set page.mapping but still
+ * dirty their pages
+ */
+ balance_dirty_pages_ratelimited(mapping);
}
+
+ /* file_update_time outside page_lock */
+ if (vma->vm_file && !vma->vm_ops->page_mkwrite)
+ file_update_time(vma->vm_file);
+
return ret;
}
@@ -3609,7 +3507,7 @@
if (!(vma->vm_flags & VM_SHARED))
return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
orig_pte);
- return do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
+ return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
}
/*
@@ -3647,7 +3545,7 @@
if (!(vma->vm_flags & VM_SHARED))
return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
orig_pte);
- return do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
+ return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
}
static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,