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    Subject[PATCH v5 11/19] mm: pagewalk: Allow walking without vma
    Date
    Since 48684a65b4e3: "mm: pagewalk: fix misbehavior of walk_page_range
    for vma(VM_PFNMAP)", page_table_walk() will report any kernel area as
    a hole, because it lacks a vma.

    This means each arch has re-implemented page table walking when needed,
    for example in the per-arch ptdump walker.

    Remove the requirement to have a vma except when trying to split huge
    pages.

    Signed-off-by: Steven Price <steven.price@arm.com>
    ---
    mm/pagewalk.c | 25 +++++++++++++++++--------
    1 file changed, 17 insertions(+), 8 deletions(-)

    diff --git a/mm/pagewalk.c b/mm/pagewalk.c
    index 98373a9f88b8..dac0c848b458 100644
    --- a/mm/pagewalk.c
    +++ b/mm/pagewalk.c
    @@ -36,7 +36,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
    do {
    again:
    next = pmd_addr_end(addr, end);
    - if (pmd_none(*pmd) || !walk->vma) {
    + if (pmd_none(*pmd)) {
    if (walk->pte_hole)
    err = walk->pte_hole(addr, next, walk);
    if (err)
    @@ -59,9 +59,14 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
    if (!walk->pte_entry)
    continue;

    - split_huge_pmd(walk->vma, pmd, addr);
    - if (pmd_trans_unstable(pmd))
    - goto again;
    + if (walk->vma) {
    + split_huge_pmd(walk->vma, pmd, addr);
    + if (pmd_trans_unstable(pmd))
    + goto again;
    + } else if (pmd_large(*pmd)) {
    + continue;
    + }
    +
    err = walk_pte_range(pmd, addr, next, walk);
    if (err)
    break;
    @@ -81,7 +86,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
    do {
    again:
    next = pud_addr_end(addr, end);
    - if (pud_none(*pud) || !walk->vma) {
    + if (pud_none(*pud)) {
    if (walk->pte_hole)
    err = walk->pte_hole(addr, next, walk);
    if (err)
    @@ -95,9 +100,13 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
    break;
    }

    - split_huge_pud(walk->vma, pud, addr);
    - if (pud_none(*pud))
    - goto again;
    + if (walk->vma) {
    + split_huge_pud(walk->vma, pud, addr);
    + if (pud_none(*pud))
    + goto again;
    + } else if (pud_large(*pud)) {
    + continue;
    + }

    if (walk->pmd_entry || walk->pte_entry)
    err = walk_pmd_range(pud, addr, next, walk);
    --
    2.20.1
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