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    Subject[patch 2/3] mmu_notifier: Callbacks to invalidate address ranges
    The invalidation of address ranges in a mm_struct needs to be
    performed when pages are removed or permissions etc change.

    invalidate_range_begin/end() is frequently called with only mmap_sem
    held. If invalidate_range_begin() is called with locks held then we
    pass a flag into invalidate_range() to indicate that no sleeping is
    possible.

    In two cases we use invalidate_range_begin/end to invalidate
    single pages because the pair allows holding off new references
    (idea by Robin Holt).

    do_wp_page(): We hold off new references while update the pte.

    xip_unmap: We are not taking the PageLock so we cannot
    use the invalidate_page mmu_rmap_notifier. invalidate_range_begin/end
    stands in.

    Comments state that mmap_sem must be held for
    remap_pfn_range() but various drivers do not seem to do this.

    Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>
    Signed-off-by: Robin Holt <holt@sgi.com>
    Signed-off-by: Christoph Lameter <clameter@sgi.com>

    ---
    mm/filemap_xip.c | 4 ++++
    mm/fremap.c | 3 +++
    mm/hugetlb.c | 3 +++
    mm/memory.c | 15 +++++++++++++--
    mm/mmap.c | 2 ++
    5 files changed, 25 insertions(+), 2 deletions(-)

    Index: linux-2.6/mm/fremap.c
    ===================================================================
    --- linux-2.6.orig/mm/fremap.c 2008-01-30 20:03:05.000000000 -0800
    +++ linux-2.6/mm/fremap.c 2008-01-30 20:05:39.000000000 -0800
    @@ -15,6 +15,7 @@
    #include <linux/rmap.h>
    #include <linux/module.h>
    #include <linux/syscalls.h>
    +#include <linux/mmu_notifier.h>

    #include <asm/mmu_context.h>
    #include <asm/cacheflush.h>
    @@ -211,7 +212,9 @@ asmlinkage long sys_remap_file_pages(uns
    spin_unlock(&mapping->i_mmap_lock);
    }

    + mmu_notifier(invalidate_range_begin, mm, start, start + size, 0);
    err = populate_range(mm, vma, start, size, pgoff);
    + mmu_notifier(invalidate_range_end, mm, 0);
    if (!err && !(flags & MAP_NONBLOCK)) {
    if (unlikely(has_write_lock)) {
    downgrade_write(&mm->mmap_sem);
    Index: linux-2.6/mm/memory.c
    ===================================================================
    --- linux-2.6.orig/mm/memory.c 2008-01-30 20:03:05.000000000 -0800
    +++ linux-2.6/mm/memory.c 2008-01-30 20:07:27.000000000 -0800
    @@ -50,6 +50,7 @@
    #include <linux/delayacct.h>
    #include <linux/init.h>
    #include <linux/writeback.h>
    +#include <linux/mmu_notifier.h>

    #include <asm/pgalloc.h>
    #include <asm/uaccess.h>
    @@ -883,13 +884,16 @@ unsigned long zap_page_range(struct vm_a
    struct mmu_gather *tlb;
    unsigned long end = address + size;
    unsigned long nr_accounted = 0;
    + int atomic = details ? (details->i_mmap_lock != 0) : 0;

    lru_add_drain();
    tlb = tlb_gather_mmu(mm, 0);
    update_hiwater_rss(mm);
    + mmu_notifier(invalidate_range_begin, mm, address, end, atomic);
    end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
    if (tlb)
    tlb_finish_mmu(tlb, address, end);
    + mmu_notifier(invalidate_range_end, mm, atomic);
    return end;
    }

    @@ -1318,7 +1322,7 @@ int remap_pfn_range(struct vm_area_struc
    {
    pgd_t *pgd;
    unsigned long next;
    - unsigned long end = addr + PAGE_ALIGN(size);
    + unsigned long start = addr, end = addr + PAGE_ALIGN(size);
    struct mm_struct *mm = vma->vm_mm;
    int err;

    @@ -1352,6 +1356,7 @@ int remap_pfn_range(struct vm_area_struc
    pfn -= addr >> PAGE_SHIFT;
    pgd = pgd_offset(mm, addr);
    flush_cache_range(vma, addr, end);
    + mmu_notifier(invalidate_range_begin, mm, start, end, 0);
    do {
    next = pgd_addr_end(addr, end);
    err = remap_pud_range(mm, pgd, addr, next,
    @@ -1359,6 +1364,7 @@ int remap_pfn_range(struct vm_area_struc
    if (err)
    break;
    } while (pgd++, addr = next, addr != end);
    + mmu_notifier(invalidate_range_end, mm, 0);
    return err;
    }
    EXPORT_SYMBOL(remap_pfn_range);
    @@ -1442,10 +1448,11 @@ int apply_to_page_range(struct mm_struct
    {
    pgd_t *pgd;
    unsigned long next;
    - unsigned long end = addr + size;
    + unsigned long start = addr, end = addr + size;
    int err;

    BUG_ON(addr >= end);
    + mmu_notifier(invalidate_range_begin, mm, start, end, 0);
    pgd = pgd_offset(mm, addr);
    do {
    next = pgd_addr_end(addr, end);
    @@ -1453,6 +1460,7 @@ int apply_to_page_range(struct mm_struct
    if (err)
    break;
    } while (pgd++, addr = next, addr != end);
    + mmu_notifier(invalidate_range_end, mm, 0);
    return err;
    }
    EXPORT_SYMBOL_GPL(apply_to_page_range);
    @@ -1630,6 +1638,8 @@ gotten:
    goto oom;
    cow_user_page(new_page, old_page, address, vma);

    + mmu_notifier(invalidate_range_begin, mm, address,
    + address + PAGE_SIZE - 1, 0);
    /*
    * Re-check the pte - we dropped the lock
    */
    @@ -1668,6 +1678,7 @@ gotten:
    page_cache_release(old_page);
    unlock:
    pte_unmap_unlock(page_table, ptl);
    + mmu_notifier(invalidate_range_end, mm, 0);
    if (dirty_page) {
    if (vma->vm_file)
    file_update_time(vma->vm_file);
    Index: linux-2.6/mm/mmap.c
    ===================================================================
    --- linux-2.6.orig/mm/mmap.c 2008-01-30 20:03:05.000000000 -0800
    +++ linux-2.6/mm/mmap.c 2008-01-30 20:05:39.000000000 -0800
    @@ -1744,11 +1744,13 @@ static void unmap_region(struct mm_struc
    lru_add_drain();
    tlb = tlb_gather_mmu(mm, 0);
    update_hiwater_rss(mm);
    + mmu_notifier(invalidate_range_begin, mm, start, end, 0);
    unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL);
    vm_unacct_memory(nr_accounted);
    free_pgtables(&tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS,
    next? next->vm_start: 0);
    tlb_finish_mmu(tlb, start, end);
    + mmu_notifier(invalidate_range_end, mm, 0);
    }

    /*
    Index: linux-2.6/mm/hugetlb.c
    ===================================================================
    --- linux-2.6.orig/mm/hugetlb.c 2008-01-30 20:03:05.000000000 -0800
    +++ linux-2.6/mm/hugetlb.c 2008-01-30 20:05:39.000000000 -0800
    @@ -14,6 +14,7 @@
    #include <linux/mempolicy.h>
    #include <linux/cpuset.h>
    #include <linux/mutex.h>
    +#include <linux/mmu_notifier.h>

    #include <asm/page.h>
    #include <asm/pgtable.h>
    @@ -743,6 +744,7 @@ void __unmap_hugepage_range(struct vm_ar
    BUG_ON(start & ~HPAGE_MASK);
    BUG_ON(end & ~HPAGE_MASK);

    + mmu_notifier(invalidate_range_begin, mm, start, end, 1);
    spin_lock(&mm->page_table_lock);
    for (address = start; address < end; address += HPAGE_SIZE) {
    ptep = huge_pte_offset(mm, address);
    @@ -763,6 +765,7 @@ void __unmap_hugepage_range(struct vm_ar
    }
    spin_unlock(&mm->page_table_lock);
    flush_tlb_range(vma, start, end);
    + mmu_notifier(invalidate_range_end, mm, 1);
    list_for_each_entry_safe(page, tmp, &page_list, lru) {
    list_del(&page->lru);
    put_page(page);
    Index: linux-2.6/mm/filemap_xip.c
    ===================================================================
    --- linux-2.6.orig/mm/filemap_xip.c 2008-01-30 20:03:05.000000000 -0800
    +++ linux-2.6/mm/filemap_xip.c 2008-01-30 20:05:39.000000000 -0800
    @@ -13,6 +13,7 @@
    #include <linux/module.h>
    #include <linux/uio.h>
    #include <linux/rmap.h>
    +#include <linux/mmu_notifier.h>
    #include <linux/sched.h>
    #include <asm/tlbflush.h>

    @@ -189,6 +190,8 @@ __xip_unmap (struct address_space * mapp
    address = vma->vm_start +
    ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
    BUG_ON(address < vma->vm_start || address >= vma->vm_end);
    + mmu_notifier(invalidate_range_begin, mm, address,
    + address + PAGE_SIZE - 1, 1);
    pte = page_check_address(page, mm, address, &ptl);
    if (pte) {
    /* Nuke the page table entry. */
    @@ -200,6 +203,7 @@ __xip_unmap (struct address_space * mapp
    pte_unmap_unlock(pte, ptl);
    page_cache_release(page);
    }
    + mmu_notifier(invalidate_range_end, mm, 1);
    }
    spin_unlock(&mapping->i_mmap_lock);
    }
    --


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