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mm: introduce do_cow_fault() 

Introduce do_cow_fault().  The function does what do_fault() does for
write page faults to private mappings.

Unlike do_fault(), do_read_fault() is relatively clean and
straight-forward.

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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2014-04-03 14:48:12 -07:00 committed by Linus Torvalds
parent e655fb2907
commit ec47c3b954
1 changed files with 62 additions and 0 deletions
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62
mm/memory.c
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@ -3354,6 +3354,62 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
return ret;
}
static int do_cow_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)
{
struct page *fault_page, *new_page;
spinlock_t *ptl;
pte_t entry, *pte;
int ret;
if (unlikely(anon_vma_prepare(vma)))
return VM_FAULT_OOM;
new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
if (!new_page)
return VM_FAULT_OOM;
if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)) {
page_cache_release(new_page);
return VM_FAULT_OOM;
}
ret = __do_fault(vma, address, pgoff, flags, &fault_page);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
goto uncharge_out;
copy_user_highpage(new_page, fault_page, address, vma);
__SetPageUptodate(new_page);
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);
goto uncharge_out;
}
flush_icache_page(vma, new_page);
entry = mk_pte(new_page, vma->vm_page_prot);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
inc_mm_counter_fast(mm, MM_ANONPAGES);
page_add_new_anon_rmap(new_page, vma, address);
set_pte_at(mm, address, pte, entry);
/* no need to invalidate: a not-present page won't be cached */
update_mmu_cache(vma, address, pte);
pte_unmap_unlock(pte, ptl);
unlock_page(fault_page);
page_cache_release(fault_page);
return ret;
uncharge_out:
mem_cgroup_uncharge_page(new_page);
page_cache_release(new_page);
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
@ -3550,6 +3606,9 @@ static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (!(flags & FAULT_FLAG_WRITE))
return do_read_fault(mm, vma, address, pmd, pgoff, flags,
orig_pte);
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);
}
@ -3585,6 +3644,9 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (!(flags & FAULT_FLAG_WRITE))
return do_read_fault(mm, vma, address, pmd, pgoff, flags,
orig_pte);
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);
}