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Date: Tue, 20 Mar 2018 22:07:29 -0700
From: John Hubbard <jhubbard@...dia.com>
To: <jglisse@...hat.com>, <linux-mm@...ck.org>
CC: Andrew Morton <akpm@...ux-foundation.org>,
<linux-kernel@...r.kernel.org>,
Evgeny Baskakov <ebaskakov@...dia.com>,
Ralph Campbell <rcampbell@...dia.com>,
Mark Hairgrove <mhairgrove@...dia.com>
Subject: Re: [PATCH 13/15] mm/hmm: factor out pte and pmd handling to simplify
hmm_vma_walk_pmd()
On 03/19/2018 07:00 PM, jglisse@...hat.com wrote:
> From: Jérôme Glisse <jglisse@...hat.com>
>
> No functional change, just create one function to handle pmd and one
> to handle pte (hmm_vma_handle_pmd() and hmm_vma_handle_pte()).
>
> Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
> Cc: Evgeny Baskakov <ebaskakov@...dia.com>
> Cc: Ralph Campbell <rcampbell@...dia.com>
> Cc: Mark Hairgrove <mhairgrove@...dia.com>
> Cc: John Hubbard <jhubbard@...dia.com>
> ---
> mm/hmm.c | 174 +++++++++++++++++++++++++++++++++++++--------------------------
> 1 file changed, 102 insertions(+), 72 deletions(-)
>
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 52cdceb35733..dc703e9c3a95 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -351,6 +351,99 @@ static int hmm_vma_walk_hole(unsigned long addr,
> return hmm_vma_walk->fault ? -EAGAIN : 0;
> }
>
> +static int hmm_vma_handle_pmd(struct mm_walk *walk,
> + unsigned long addr,
> + unsigned long end,
> + uint64_t *pfns,
Hi Jerome,
Nice cleanup, it makes it much easier to follow the code now.
Let's please rename the pfns argument above to "pfn", because in this
helper (and the _pte helper too), there is only one pfn involved, rather
than an array of them.
> + pmd_t pmd)
> +{
> + struct hmm_vma_walk *hmm_vma_walk = walk->private;
> + unsigned long pfn, i;
> + uint64_t flag = 0;
> +
> + if (pmd_protnone(pmd))
> + return hmm_vma_walk_hole(addr, end, walk);
> +
> + if ((hmm_vma_walk->fault & hmm_vma_walk->write) && !pmd_write(pmd))
> + return hmm_vma_walk_hole(addr, end, walk);
> +
> + pfn = pmd_pfn(pmd) + pte_index(addr);
> + flag |= pmd_write(pmd) ? HMM_PFN_WRITE : 0;
> + for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++)
> + pfns[i] = hmm_pfn_from_pfn(pfn) | flag;
> + hmm_vma_walk->last = end;
> + return 0;
> +}
> +
> +static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
> + unsigned long end, pmd_t *pmdp, pte_t *ptep,
> + uint64_t *pfns)
Same thing here: rename pfns --> pfn.
I moved diffs around to attempt to confirm that this is just a refactoring,
and it does look the same. It's easy to overlook things here, but:
Reviewed-by: John Hubbard <jhubbard@...dia.com>
thanks,
--
John Hubbard
NVIDIA
> +{
> + struct hmm_vma_walk *hmm_vma_walk = walk->private;
> + struct vm_area_struct *vma = walk->vma;
> + pte_t pte = *ptep;
> +
> + *pfns = 0;
> +
> + if (pte_none(pte)) {
> + *pfns = 0;
> + if (hmm_vma_walk->fault)
> + goto fault;
> + return 0;
> + }
> +
> + if (!pte_present(pte)) {
> + swp_entry_t entry = pte_to_swp_entry(pte);
> +
> + if (!non_swap_entry(entry)) {
> + if (hmm_vma_walk->fault)
> + goto fault;
> + return 0;
> + }
> +
> + /*
> + * This is a special swap entry, ignore migration, use
> + * device and report anything else as error.
> + */
> + if (is_device_private_entry(entry)) {
> + *pfns = hmm_pfn_from_pfn(swp_offset(entry));
> + if (is_write_device_private_entry(entry)) {
> + *pfns |= HMM_PFN_WRITE;
> + } else if ((hmm_vma_walk->fault & hmm_vma_walk->write))
> + goto fault;
> + *pfns |= HMM_PFN_DEVICE_PRIVATE;
> + return 0;
> + }
> +
> + if (is_migration_entry(entry)) {
> + if (hmm_vma_walk->fault) {
> + pte_unmap(ptep);
> + hmm_vma_walk->last = addr;
> + migration_entry_wait(vma->vm_mm,
> + pmdp, addr);
> + return -EAGAIN;
> + }
> + return 0;
> + }
> +
> + /* Report error for everything else */
> + *pfns = HMM_PFN_ERROR;
> + return -EFAULT;
> + }
> +
> + if ((hmm_vma_walk->fault & hmm_vma_walk->write) && !pte_write(pte))
> + goto fault;
> +
> + *pfns = hmm_pfn_from_pfn(pte_pfn(pte));
> + *pfns |= pte_write(pte) ? HMM_PFN_WRITE : 0;
> + return 0;
> +
> +fault:
> + pte_unmap(ptep);
> + /* Fault any virtual address we were ask to fault */
> + return hmm_vma_walk_hole(addr, end, walk);
> +}
> +
> static int hmm_vma_walk_pmd(pmd_t *pmdp,
> unsigned long start,
> unsigned long end,
> @@ -358,25 +451,20 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
> {
> struct hmm_vma_walk *hmm_vma_walk = walk->private;
> struct hmm_range *range = hmm_vma_walk->range;
> - struct vm_area_struct *vma = walk->vma;
> uint64_t *pfns = range->pfns;
> unsigned long addr = start, i;
> - bool write_fault;
> pte_t *ptep;
>
> i = (addr - range->start) >> PAGE_SHIFT;
> - write_fault = hmm_vma_walk->fault & hmm_vma_walk->write;
>
> again:
> if (pmd_none(*pmdp))
> return hmm_vma_walk_hole(start, end, walk);
>
> - if (pmd_huge(*pmdp) && vma->vm_flags & VM_HUGETLB)
> + if (pmd_huge(*pmdp) && (range->vma->vm_flags & VM_HUGETLB))
> return hmm_pfns_bad(start, end, walk);
>
> if (pmd_devmap(*pmdp) || pmd_trans_huge(*pmdp)) {
> - unsigned long pfn;
> - uint64_t flag = 0;
> pmd_t pmd;
>
> /*
> @@ -392,17 +480,8 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
> barrier();
> if (!pmd_devmap(pmd) && !pmd_trans_huge(pmd))
> goto again;
> - if (pmd_protnone(pmd))
> - return hmm_vma_walk_hole(start, end, walk);
>
> - if (write_fault && !pmd_write(pmd))
> - return hmm_vma_walk_hole(start, end, walk);
> -
> - pfn = pmd_pfn(pmd) + pte_index(addr);
> - flag |= pmd_write(pmd) ? HMM_PFN_WRITE : 0;
> - for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
> - pfns[i] = hmm_pfn_from_pfn(pfn) | flag;
> - return 0;
> + return hmm_vma_handle_pmd(walk, addr, end, &pfns[i], pmd);
> }
>
> if (pmd_bad(*pmdp))
> @@ -410,67 +489,18 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
>
> ptep = pte_offset_map(pmdp, addr);
> for (; addr < end; addr += PAGE_SIZE, ptep++, i++) {
> - pte_t pte = *ptep;
> + int r;
>
> - pfns[i] = 0;
> -
> - if (pte_none(pte)) {
> - pfns[i] = 0;
> - if (hmm_vma_walk->fault)
> - goto fault;
> - continue;
> - }
> -
> - if (!pte_present(pte)) {
> - swp_entry_t entry = pte_to_swp_entry(pte);
> -
> - if (!non_swap_entry(entry)) {
> - if (hmm_vma_walk->fault)
> - goto fault;
> - continue;
> - }
> -
> - /*
> - * This is a special swap entry, ignore migration, use
> - * device and report anything else as error.
> - */
> - if (is_device_private_entry(entry)) {
> - pfns[i] = hmm_pfn_from_pfn(swp_offset(entry));
> - if (is_write_device_private_entry(entry)) {
> - pfns[i] |= HMM_PFN_WRITE;
> - } else if (write_fault)
> - goto fault;
> - pfns[i] |= HMM_PFN_DEVICE_PRIVATE;
> - } else if (is_migration_entry(entry)) {
> - if (hmm_vma_walk->fault) {
> - pte_unmap(ptep);
> - hmm_vma_walk->last = addr;
> - migration_entry_wait(vma->vm_mm,
> - pmdp, addr);
> - return -EAGAIN;
> - }
> - continue;
> - } else {
> - /* Report error for everything else */
> - pfns[i] = HMM_PFN_ERROR;
> - }
> - continue;
> + r = hmm_vma_handle_pte(walk, addr, end, pmdp, ptep, &pfns[i]);
> + if (r) {
> + /* hmm_vma_handle_pte() did unmap pte directory */
> + hmm_vma_walk->last = addr;
> + return r;
> }
> -
> - if (write_fault && !pte_write(pte))
> - goto fault;
> -
> - pfns[i] = hmm_pfn_from_pfn(pte_pfn(pte));
> - pfns[i] |= pte_write(pte) ? HMM_PFN_WRITE : 0;
> - continue;
> -
> -fault:
> - pte_unmap(ptep);
> - /* Fault any virtual address we were ask to fault */
> - return hmm_vma_walk_hole(start, end, walk);
> }
> pte_unmap(ptep - 1);
>
> + hmm_vma_walk->last = addr;
> return 0;
> }
>
>
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