[PATCH] powerpc: platform: cell: spufs: Change return type to vm_fault_t

[PATCH] powerpc: platform: cell: spufs: Change return type to vm_fault_t

[Souptick Joarder]

Use new return type vm_fault_t for fault handler. For
now, this is just documenting that the function returns
a VM_FAULT value rather than an errno. Once all instances
are converted, vm_fault_t will become a distinct type.

Reference id -> 1c8f422059ae ("mm: change return type to
vm_fault_t")

Previously vm_insert_pfn() returns err but driver returns 
VM_FAULT_NOPAGE as default. The new function vmf_insert_pfn()
will replace this inefficiency by returning correct VM_FAULT_*
type.

vmf_handle_error is a inline wrapper function which
will convert error number to vm_fault_t type err.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
---
 arch/powerpc/platforms/cell/spufs/file.c | 37 ++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c
index 469bdd0..a1dca9a 100644
--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -232,12 +232,13 @@ static ssize_t spufs_attr_write(struct file *file, const char __user *buf,
 	return size;
 }
 
-static int
+static vm_fault_t
 spufs_mem_mmap_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct spu_context *ctx	= vma->vm_file->private_data;
 	unsigned long pfn, offset;
+	vm_fault_t ret;
 
 	offset = vmf->pgoff << PAGE_SHIFT;
 	if (offset >= LS_SIZE)
@@ -256,11 +257,11 @@ static ssize_t spufs_attr_write(struct file *file, const char __user *buf,
 		vma->vm_page_prot = pgprot_noncached_wc(vma->vm_page_prot);
 		pfn = (ctx->spu->local_store_phys + offset) >> PAGE_SHIFT;
 	}
-	vm_insert_pfn(vma, vmf->address, pfn);
+	ret = vmf_insert_pfn(vma, vmf->address, pfn);
 
 	spu_release(ctx);
 
-	return VM_FAULT_NOPAGE;
+	return ret;
 }
 
 static int spufs_mem_mmap_access(struct vm_area_struct *vma,
@@ -312,13 +313,19 @@ static int spufs_mem_mmap(struct file *file, struct vm_area_struct *vma)
 	.mmap			= spufs_mem_mmap,
 };
 
-static int spufs_ps_fault(struct vm_fault *vmf,
+static inline vm_fault_t vmf_handle_error(int err)
+{
+	return VM_FAULT_NOPAGE;
+}
+
+static vm_fault_t spufs_ps_fault(struct vm_fault *vmf,
 				    unsigned long ps_offs,
 				    unsigned long ps_size)
 {
 	struct spu_context *ctx = vmf->vma->vm_file->private_data;
 	unsigned long area, offset = vmf->pgoff << PAGE_SHIFT;
-	int ret = 0;
+	int err = 0;
+	vm_fault_t ret = VM_FAULT_NOPAGE;
 
 	spu_context_nospu_trace(spufs_ps_fault__enter, ctx);
 
@@ -349,12 +356,14 @@ static int spufs_ps_fault(struct vm_fault *vmf,
 	if (ctx->state == SPU_STATE_SAVED) {
 		up_read(&current->mm->mmap_sem);
 		spu_context_nospu_trace(spufs_ps_fault__sleep, ctx);
-		ret = spufs_wait(ctx->run_wq, ctx->state == SPU_STATE_RUNNABLE);
+		err = spufs_wait(ctx->run_wq, ctx->state == SPU_STATE_RUNNABLE);
+		ret = vmf_handle_error(err);
 		spu_context_trace(spufs_ps_fault__wake, ctx, ctx->spu);
 		down_read(&current->mm->mmap_sem);
 	} else {
 		area = ctx->spu->problem_phys + ps_offs;
-		vm_insert_pfn(vmf->vma, vmf->address, (area + offset) >> PAGE_SHIFT);
+		ret = vmf_insert_pfn(vmf->vma, vmf->address,
+				(area + offset) >> PAGE_SHIFT);
 		spu_context_trace(spufs_ps_fault__insert, ctx, ctx->spu);
 	}
 
@@ -363,11 +372,11 @@ static int spufs_ps_fault(struct vm_fault *vmf,
 
 refault:
 	put_spu_context(ctx);
-	return VM_FAULT_NOPAGE;
+	return ret;
 }
 
 #if SPUFS_MMAP_4K
-static int spufs_cntl_mmap_fault(struct vm_fault *vmf)
+static vm_fault_t spufs_cntl_mmap_fault(struct vm_fault *vmf)
 {
 	return spufs_ps_fault(vmf, 0x4000, SPUFS_CNTL_MAP_SIZE);
 }
@@ -1040,7 +1049,7 @@ static ssize_t spufs_signal1_write(struct file *file, const char __user *buf,
 	return 4;
 }
 
-static int
+static vm_fault_t
 spufs_signal1_mmap_fault(struct vm_fault *vmf)
 {
 #if SPUFS_SIGNAL_MAP_SIZE == 0x1000
@@ -1178,7 +1187,7 @@ static ssize_t spufs_signal2_write(struct file *file, const char __user *buf,
 }
 
 #if SPUFS_MMAP_4K
-static int
+static vm_fault_t
 spufs_signal2_mmap_fault(struct vm_fault *vmf)
 {
 #if SPUFS_SIGNAL_MAP_SIZE == 0x1000
@@ -1307,7 +1316,7 @@ static u64 spufs_signal2_type_get(struct spu_context *ctx)
 		       spufs_signal2_type_set, "%llu\n", SPU_ATTR_ACQUIRE);
 
 #if SPUFS_MMAP_4K
-static int
+static vm_fault_t
 spufs_mss_mmap_fault(struct vm_fault *vmf)
 {
 	return spufs_ps_fault(vmf, 0x0000, SPUFS_MSS_MAP_SIZE);
@@ -1369,7 +1378,7 @@ static int spufs_mss_open(struct inode *inode, struct file *file)
 	.llseek  = no_llseek,
 };
 
-static int
+static vm_fault_t
 spufs_psmap_mmap_fault(struct vm_fault *vmf)
 {
 	return spufs_ps_fault(vmf, 0x0000, SPUFS_PS_MAP_SIZE);
@@ -1429,7 +1438,7 @@ static int spufs_psmap_open(struct inode *inode, struct file *file)
 
 
 #if SPUFS_MMAP_4K
-static int
+static vm_fault_t
 spufs_mfc_mmap_fault(struct vm_fault *vmf)
 {
 	return spufs_ps_fault(vmf, 0x3000, SPUFS_MFC_MAP_SIZE);
-- 
1.9.1

Re: [PATCH] powerpc: platform: cell: spufs: Change return type to vm_fault_t

[Arnd Bergmann]

On Tue, Apr 17, 2018 at 9:20 PM, Souptick Joarder <jrdr.linux@gmail.com> wrote:
> Use new return type vm_fault_t for fault handler. For
> now, this is just documenting that the function returns
> a VM_FAULT value rather than an errno. Once all instances
> are converted, vm_fault_t will become a distinct type.
>
> Reference id -> 1c8f422059ae ("mm: change return type to
> vm_fault_t")
>
> Previously vm_insert_pfn() returns err but driver returns
> VM_FAULT_NOPAGE as default. The new function vmf_insert_pfn()
> will replace this inefficiency by returning correct VM_FAULT_*
> type.
>
> vmf_handle_error is a inline wrapper function which
> will convert error number to vm_fault_t type err.
>
> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>

Acked-by: Arnd Bergmann <arnd@arndb.de>

Re: [PATCH] powerpc: platform: cell: spufs: Change return type to vm_fault_t

[Matthew Wilcox]

On Wed, Apr 18, 2018 at 12:50:38AM +0530, Souptick Joarder wrote:
> Use new return type vm_fault_t for fault handler. For
> now, this is just documenting that the function returns
> a VM_FAULT value rather than an errno. Once all instances
> are converted, vm_fault_t will become a distinct type.
> 
> Reference id -> 1c8f422059ae ("mm: change return type to
> vm_fault_t")
> 
> Previously vm_insert_pfn() returns err but driver returns 
> VM_FAULT_NOPAGE as default. The new function vmf_insert_pfn()
> will replace this inefficiency by returning correct VM_FAULT_*
> type.
> 
> vmf_handle_error is a inline wrapper function which
> will convert error number to vm_fault_t type err.

I think you sent the wrong version of this one ...

The commit message should mention that we're fixing a minor bug, that
the error from vm_insert_pfn() was being ignored and the effect of this
is likely to be only felt in OOM situations.

> @@ -256,11 +257,11 @@ static ssize_t spufs_attr_write(struct file *file, const char __user *buf,
>  		vma->vm_page_prot = pgprot_noncached_wc(vma->vm_page_prot);
>  		pfn = (ctx->spu->local_store_phys + offset) >> PAGE_SHIFT;
>  	}
> -	vm_insert_pfn(vma, vmf->address, pfn);
> +	ret = vmf_insert_pfn(vma, vmf->address, pfn);
>  
>  	spu_release(ctx);
>  
> -	return VM_FAULT_NOPAGE;
> +	return ret;
>  }

I thought I said not to introduce vmf_handle_error(), because it's too
trivial and obfuscates what's actually going on.

> -static int spufs_ps_fault(struct vm_fault *vmf,
> +static inline vm_fault_t vmf_handle_error(int err)
> +{
> +	return VM_FAULT_NOPAGE;
> +}
> +

Re-reading spufs_ps_fault(), I wouldn't change anything inside it.  Just
change its return type to vm_fault_t and call it done.

Re: [PATCH] powerpc: platform: cell: spufs: Change return type to vm_fault_t

[Souptick Joarder]

On Wed, Apr 18, 2018 at 2:17 AM, Matthew Wilcox <willy@infradead.org> wrote:
> On Wed, Apr 18, 2018 at 12:50:38AM +0530, Souptick Joarder wrote:
>> Use new return type vm_fault_t for fault handler. For
>> now, this is just documenting that the function returns
>> a VM_FAULT value rather than an errno. Once all instances
>> are converted, vm_fault_t will become a distinct type.
>>
>> Reference id -> 1c8f422059ae ("mm: change return type to
>> vm_fault_t")
>>
>> Previously vm_insert_pfn() returns err but driver returns
>> VM_FAULT_NOPAGE as default. The new function vmf_insert_pfn()
>> will replace this inefficiency by returning correct VM_FAULT_*
>> type.
>>
>> vmf_handle_error is a inline wrapper function which
>> will convert error number to vm_fault_t type err.
>
> I think you sent the wrong version of this one ...
>
> The commit message should mention that we're fixing a minor bug, that
> the error from vm_insert_pfn() was being ignored and the effect of this
> is likely to be only felt in OOM situations.

Ok, I will add this.
>
>> @@ -256,11 +257,11 @@ static ssize_t spufs_attr_write(struct file *file, const char __user *buf,
>>               vma->vm_page_prot = pgprot_noncached_wc(vma->vm_page_prot);
>>               pfn = (ctx->spu->local_store_phys + offset) >> PAGE_SHIFT;
>>       }
>> -     vm_insert_pfn(vma, vmf->address, pfn);
>> +     ret = vmf_insert_pfn(vma, vmf->address, pfn);
>>
>>       spu_release(ctx);
>>
>> -     return VM_FAULT_NOPAGE;
>> +     return ret;
>>  }
>
> I thought I said not to introduce vmf_handle_error(), because it's too
> trivial and obfuscates what's actually going on.
>
>> -static int spufs_ps_fault(struct vm_fault *vmf,
>> +static inline vm_fault_t vmf_handle_error(int err)
>> +{
>> +     return VM_FAULT_NOPAGE;
>> +}
>> +
>
> Re-reading spufs_ps_fault(), I wouldn't change anything inside it.  Just
> change its return type to vm_fault_t and call it done.

In that case, return value of spufs_wait() has to changed
to VM_FAULT_ type and we end with changing all the
references where spufs_wait() is called. I think we shouldn't
go with that approach. That's the reason I introduce inline
vmf_handle_error() and convert err to VM_FAULT_ type.

Re: [PATCH] powerpc: platform: cell: spufs: Change return type to vm_fault_t

[Matthew Wilcox]

On Thu, Apr 19, 2018 at 12:34:15AM +0530, Souptick Joarder wrote:
> > Re-reading spufs_ps_fault(), I wouldn't change anything inside it.  Just
> > change its return type to vm_fault_t and call it done.
> 
> In that case, return value of spufs_wait() has to changed
> to VM_FAULT_ type and we end with changing all the
> references where spufs_wait() is called. I think we shouldn't
> go with that approach. That's the reason I introduce inline
> vmf_handle_error() and convert err to VM_FAULT_ type.

No, don't change the type of 'ret' or spufs_wait.  Just do this:

-static int spufs_ps_fault(struct vm_fault *vmf,
+static vm_fault_t spufs_ps_fault(struct vm_fault *vmf,
                                    unsigned long ps_offs,
                                    unsigned long ps_size)

Re: [PATCH] powerpc: platform: cell: spufs: Change return type to vm_fault_t

[Souptick Joarder]

On Thu, Apr 19, 2018 at 12:57 AM, Matthew Wilcox <willy@infradead.org> wrote:
> On Thu, Apr 19, 2018 at 12:34:15AM +0530, Souptick Joarder wrote:
>> > Re-reading spufs_ps_fault(), I wouldn't change anything inside it.  Just
>> > change its return type to vm_fault_t and call it done.
>>
>> In that case, return value of spufs_wait() has to changed
>> to VM_FAULT_ type and we end with changing all the
>> references where spufs_wait() is called. I think we shouldn't
>> go with that approach. That's the reason I introduce inline
>> vmf_handle_error() and convert err to VM_FAULT_ type.
>
> No, don't change the type of 'ret' or spufs_wait.  Just do this:
>
> -static int spufs_ps_fault(struct vm_fault *vmf,
> +static vm_fault_t spufs_ps_fault(struct vm_fault *vmf,
>                                     unsigned long ps_offs,
>                                     unsigned long ps_size)
>

Agree. but vm_insert_pfn should be replaced with new
vmf_insert_pfn, right ?

Re: [PATCH] powerpc: platform: cell: spufs: Change return type to vm_fault_t

[Matthew Wilcox]

On Thu, Apr 19, 2018 at 01:03:43AM +0530, Souptick Joarder wrote:
> On Thu, Apr 19, 2018 at 12:57 AM, Matthew Wilcox <willy@infradead.org> wrote:
> > On Thu, Apr 19, 2018 at 12:34:15AM +0530, Souptick Joarder wrote:
> >> > Re-reading spufs_ps_fault(), I wouldn't change anything inside it.  Just
> >> > change its return type to vm_fault_t and call it done.
> >>
> >> In that case, return value of spufs_wait() has to changed
> >> to VM_FAULT_ type and we end with changing all the
> >> references where spufs_wait() is called. I think we shouldn't
> >> go with that approach. That's the reason I introduce inline
> >> vmf_handle_error() and convert err to VM_FAULT_ type.
> >
> > No, don't change the type of 'ret' or spufs_wait.  Just do this:
> >
> > -static int spufs_ps_fault(struct vm_fault *vmf,
> > +static vm_fault_t spufs_ps_fault(struct vm_fault *vmf,
> >                                     unsigned long ps_offs,
> >                                     unsigned long ps_size)
> >
> 
> Agree. but vm_insert_pfn should be replaced with new
> vmf_insert_pfn, right ?

Oh, right, sorry, I missed that.

So something like this:

-static int spufs_ps_fault(struct vm_fault *vmf,
+static vm_fault_t spufs_ps_fault(struct vm_fault *vmf,
                                    unsigned long ps_offs,
                                    unsigned long ps_size)
 {
        struct spu_context *ctx = vmf->vma->vm_file->private_data;
        unsigned long area, offset = vmf->pgoff << PAGE_SHIFT;
-       int ret = 0;
+       int err = 0;
+       vm_fault_t ret = VM_FAULT_NOPAGE;
 
        spu_context_nospu_trace(spufs_ps_fault__enter, ctx);
 
@@ -349,21 +350,22 @@ static int spufs_ps_fault(struct vm_fault *vmf,
        if (ctx->state == SPU_STATE_SAVED) {
                up_read(&current->mm->mmap_sem);
                spu_context_nospu_trace(spufs_ps_fault__sleep, ctx);
-               ret = spufs_wait(ctx->run_wq, ctx->state == SPU_STATE_RUNNABLE);
+               err = spufs_wait(ctx->run_wq, ctx->state == SPU_STATE_RUNNABLE);
                spu_context_trace(spufs_ps_fault__wake, ctx, ctx->spu);
                down_read(&current->mm->mmap_sem);
        } else {
                area = ctx->spu->problem_phys + ps_offs;
-               vm_insert_pfn(vmf->vma, vmf->address, (area + offset) >> PAGE_SHIFT);
+               ret = vmf_insert_pfn(vmf->vma, vmf->address,
+                               (area + offset) >> PAGE_SHIFT);
                spu_context_trace(spufs_ps_fault__insert, ctx, ctx->spu);
        }
 
-       if (!ret)
+       if (!err)
                spu_release(ctx);
 
 refault:
        put_spu_context(ctx);
-       return VM_FAULT_NOPAGE;
+       return ret;
 }