Re: [PATCH v6 09/10] device-dax: set mapping prior to vmf_insert_pfn{,_pmd,pud}()

2021-11-29 Thread Joao Martins 
On 11/29/21 07:32, Christoph Hellwig wrote:
> On Fri, Nov 26, 2021 at 06:39:39PM +, Joao Martins wrote:
>> @@ -230,23 +235,18 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault 
>> *vmf,
>>  id = dax_read_lock();
>>  switch (pe_size) {
>>  case PE_SIZE_PTE:
>> -fault_size = PAGE_SIZE;
>>  rc = __dev_dax_pte_fault(dev_dax, vmf, &pfn);
>>  break;
>>  case PE_SIZE_PMD:
>> -fault_size = PMD_SIZE;
>>  rc = __dev_dax_pmd_fault(dev_dax, vmf, &pfn);
>>  break;
>>  case PE_SIZE_PUD:
>> -fault_size = PUD_SIZE;
>>  rc = __dev_dax_pud_fault(dev_dax, vmf, &pfn);
>>  break;
>>  default:
>>  rc = VM_FAULT_SIGBUS;
>>  }
>>
>>  dax_read_unlock(id);
> 
> I wonder if if would make sense to move dax_read_lock / dax_read_unlock
> Ń–nto the individul helpers as well now.  That way you could directly
> return from the switch. 

Hmmm -- if by individual helpers moving to __dev_dax_{pte,pmd,pud}_fault()
it would be slightly less straighforward. Unless you might mean to move
to check_vma() (around the dax_alive() check) and that might actually
remove the opencoding of dax_read_lock in dax_mmap() even.

I would rather prefer that this cleanup around dax_read_{un,}lock is
a separate patch separate to this series, unless you feel strongly that
it needs to be part of this set.

> Aso it seems like pfn is only an input
> parameter now and doesn't need to be passed by reference.
> 
It's actually just an output parameter (that dax_set_mapping would then use).

The fault handlers in device-dax use vmf->address to calculate pfn that they
insert in the page table entry. After this patch we can actually just remove
@pfn argument.

Joao

Re: [PATCH v6 09/10] device-dax: set mapping prior to vmf_insert_pfn{,_pmd,pud}()

2021-11-29 Thread Christoph Hellwig 
On Mon, Nov 29, 2021 at 03:49:46PM +, Joao Martins wrote:
> Hmmm -- if by individual helpers moving to __dev_dax_{pte,pmd,pud}_fault()
> it would be slightly less straighforward. Unless you might mean to move
> to check_vma() (around the dax_alive() check) and that might actually
> remove the opencoding of dax_read_lock in dax_mmap() even.
> 
> I would rather prefer that this cleanup around dax_read_{un,}lock is
> a separate patch separate to this series, unless you feel strongly that
> it needs to be part of this set.

Feel free to keep it as-is.

Re: [PATCH v6 09/10] device-dax: set mapping prior to vmf_insert_pfn{,_pmd,pud}()

2021-11-29 Thread Joao Martins 
On 11/29/21 15:49, Joao Martins wrote:
> On 11/29/21 07:32, Christoph Hellwig wrote:
>> On Fri, Nov 26, 2021 at 06:39:39PM +, Joao Martins wrote:
>> Aso it seems like pfn is only an input
>> parameter now and doesn't need to be passed by reference.
>>
> It's actually just an output parameter (that dax_set_mapping would then use).
> 
> The fault handlers in device-dax use vmf->address to calculate pfn that they
> insert in the page table entry. After this patch we can actually just remove
> @pfn argument.

I've added your suggestion as a cleanup patch between 9 and current 10 (11 in 
v7):

>8

>From 999cec9efa757b82f435124518b042caeb51bde6 Mon Sep 17 00:00:00 2001
From: Joao Martins 
Date: Mon, 29 Nov 2021 11:12:00 -0500
Subject: [PATCH] device-dax: remove pfn from __dev_dax_{pte,pmd,pud}_fault()

After moving the page mapping to be set prior to pte insertion, the pfn
in dev_dax_huge_fault() no longer is necessary.  Remove it, as well as
the @pfn argument passed to the internal fault handler helpers.

Suggested-by: Christoph Hellwig 
Signed-off-by: Joao Martins 
---
 drivers/dax/device.c | 34 ++
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 19a6b86486ce..914368164e05 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -95,10 +95,11 @@ static void dax_set_mapping(struct vm_fault *vmf, pfn_t pfn,
 }

 static vm_fault_t __dev_dax_pte_fault(struct dev_dax *dev_dax,
-   struct vm_fault *vmf, pfn_t *pfn)
+   struct vm_fault *vmf)
 {
struct device *dev = &dev_dax->dev;
phys_addr_t phys;
+   pfn_t pfn;
unsigned int fault_size = PAGE_SIZE;

if (check_vma(dev_dax, vmf->vma, __func__))
@@ -119,20 +120,21 @@ static vm_fault_t __dev_dax_pte_fault(struct dev_dax 
*dev_dax,
return VM_FAULT_SIGBUS;
}

-   *pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);
+   pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);

-   dax_set_mapping(vmf, *pfn, fault_size);
+   dax_set_mapping(vmf, pfn, fault_size);

-   return vmf_insert_mixed(vmf->vma, vmf->address, *pfn);
+   return vmf_insert_mixed(vmf->vma, vmf->address, pfn);
 }

 static vm_fault_t __dev_dax_pmd_fault(struct dev_dax *dev_dax,
-   struct vm_fault *vmf, pfn_t *pfn)
+   struct vm_fault *vmf)
 {
unsigned long pmd_addr = vmf->address & PMD_MASK;
struct device *dev = &dev_dax->dev;
phys_addr_t phys;
pgoff_t pgoff;
+   pfn_t pfn;
unsigned int fault_size = PMD_SIZE;

if (check_vma(dev_dax, vmf->vma, __func__))
@@ -161,21 +163,22 @@ static vm_fault_t __dev_dax_pmd_fault(struct dev_dax 
*dev_dax,
return VM_FAULT_SIGBUS;
}

-   *pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);
+   pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);

-   dax_set_mapping(vmf, *pfn, fault_size);
+   dax_set_mapping(vmf, pfn, fault_size);

-   return vmf_insert_pfn_pmd(vmf, *pfn, vmf->flags & FAULT_FLAG_WRITE);
+   return vmf_insert_pfn_pmd(vmf, pfn, vmf->flags & FAULT_FLAG_WRITE);
 }
 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 static vm_fault_t __dev_dax_pud_fault(struct dev_dax *dev_dax,
-   struct vm_fault *vmf, pfn_t *pfn)
+   struct vm_fault *vmf)
 {
unsigned long pud_addr = vmf->address & PUD_MASK;
struct device *dev = &dev_dax->dev;
phys_addr_t phys;
pgoff_t pgoff;
+   pfn_t pfn;
unsigned int fault_size = PUD_SIZE;


@@ -205,11 +208,11 @@ static vm_fault_t __dev_dax_pud_fault(struct dev_dax 
*dev_dax,
return VM_FAULT_SIGBUS;
}

-   *pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);
+   pfn = phys_to_pfn_t(phys, PFN_DEV|PFN_MAP);

-   dax_set_mapping(vmf, *pfn, fault_size);
+   dax_set_mapping(vmf, pfn, fault_size);

-   return vmf_insert_pfn_pud(vmf, *pfn, vmf->flags & FAULT_FLAG_WRITE);
+   return vmf_insert_pfn_pud(vmf, pfn, vmf->flags & FAULT_FLAG_WRITE);
 }
 #else
 static vm_fault_t __dev_dax_pud_fault(struct dev_dax *dev_dax,
@@ -225,7 +228,6 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
struct file *filp = vmf->vma->vm_file;
vm_fault_t rc = VM_FAULT_SIGBUS;
int id;
-   pfn_t pfn;
struct dev_dax *dev_dax = filp->private_data;

dev_dbg(&dev_dax->dev, "%s: %s (%#lx - %#lx) size = %d\n", 
current->comm,
@@ -235,13 +237,13 @@ static vm_fault_t dev_dax_huge_fault(struct vm_fault *vmf,
id = dax_read_lock();
switch (pe_size) {
case PE_SIZE_PTE:
-   rc = __dev_dax_pte_fault(dev_dax, vmf, &pfn);
+   rc = __dev_dax_pte_fault(dev_dax, vmf);
break;
case PE_SIZE_PMD:
-   rc = __dev_dax_pmd_fault(dev_dax, vmf, &pfn);
+