linux-kernel - Re: [PATCH] misc: ocxl: Change return type for fault handler

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Message-Id: <5c6942da-c847-c53a-a571-4ec96f2a993d@linux.ibm.com>
Date:   Thu, 14 Jun 2018 18:06:56 +0200
From:   Frederic Barrat <fbarrat@...ux.ibm.com>
To:     Souptick Joarder <jrdr.linux@...il.com>, willy@...radead.org,
        fbarrat@...ux.vnet.ibm.com, andrew.donnellan@....ibm.com,
        arnd@...db.de, gregkh@...uxfoundation.org
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        sabyasachi.linux@...il.com, brajeswar.linux@...il.com
Subject: Re: [PATCH] misc: ocxl: Change return type for fault handler



Le 11/06/2018 à 22:29, Souptick Joarder a écrit :
> 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.
> 
> Ref-> commit 1c8f422059ae ("mm: change return type to vm_fault_t")
> 
> There is an existing bug when vm_insert_pfn() can return
> ENOMEM which was ignored and VM_FAULT_NOPAGE returned as
> default. The new inline vmf_insert_pfn() has removed
> this inefficiency by returning correct vm_fault_ type.
> 
> Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> ---

Thanks!

Tested and
Acked-by: Frederic Barrat <fbarrat@...ux.vnet.ibm.com>


>   drivers/misc/ocxl/context.c | 22 +++++++++++-----------
>   drivers/misc/ocxl/sysfs.c   |  5 ++---
>   2 files changed, 13 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/misc/ocxl/context.c b/drivers/misc/ocxl/context.c
> index 909e880..98daf91 100644
> --- a/drivers/misc/ocxl/context.c
> +++ b/drivers/misc/ocxl/context.c
> @@ -83,7 +83,7 @@ int ocxl_context_attach(struct ocxl_context *ctx, u64 amr)
>   	return rc;
>   }
> 
> -static int map_afu_irq(struct vm_area_struct *vma, unsigned long address,
> +static vm_fault_t map_afu_irq(struct vm_area_struct *vma, unsigned long address,
>   		u64 offset, struct ocxl_context *ctx)
>   {
>   	u64 trigger_addr;
> @@ -92,15 +92,15 @@ static int map_afu_irq(struct vm_area_struct *vma, unsigned long address,
>   	if (!trigger_addr)
>   		return VM_FAULT_SIGBUS;
> 
> -	vm_insert_pfn(vma, address, trigger_addr >> PAGE_SHIFT);
> -	return VM_FAULT_NOPAGE;
> +	return vmf_insert_pfn(vma, address, trigger_addr >> PAGE_SHIFT);
>   }
> 
> -static int map_pp_mmio(struct vm_area_struct *vma, unsigned long address,
> +static vm_fault_t map_pp_mmio(struct vm_area_struct *vma, unsigned long address,
>   		u64 offset, struct ocxl_context *ctx)
>   {
>   	u64 pp_mmio_addr;
>   	int pasid_off;
> +	vm_fault_t ret;
> 
>   	if (offset >= ctx->afu->config.pp_mmio_stride)
>   		return VM_FAULT_SIGBUS;
> @@ -118,27 +118,27 @@ static int map_pp_mmio(struct vm_area_struct *vma, unsigned long address,
>   		pasid_off * ctx->afu->config.pp_mmio_stride +
>   		offset;
> 
> -	vm_insert_pfn(vma, address, pp_mmio_addr >> PAGE_SHIFT);
> +	ret = vmf_insert_pfn(vma, address, pp_mmio_addr >> PAGE_SHIFT);
>   	mutex_unlock(&ctx->status_mutex);
> -	return VM_FAULT_NOPAGE;
> +	return ret;
>   }
> 
> -static int ocxl_mmap_fault(struct vm_fault *vmf)
> +static vm_fault_t ocxl_mmap_fault(struct vm_fault *vmf)
>   {
>   	struct vm_area_struct *vma = vmf->vma;
>   	struct ocxl_context *ctx = vma->vm_file->private_data;
>   	u64 offset;
> -	int rc;
> +	vm_fault_t ret;
> 
>   	offset = vmf->pgoff << PAGE_SHIFT;
>   	pr_debug("%s: pasid %d address 0x%lx offset 0x%llx\n", __func__,
>   		ctx->pasid, vmf->address, offset);
> 
>   	if (offset < ctx->afu->irq_base_offset)
> -		rc = map_pp_mmio(vma, vmf->address, offset, ctx);
> +		ret = map_pp_mmio(vma, vmf->address, offset, ctx);
>   	else
> -		rc = map_afu_irq(vma, vmf->address, offset, ctx);
> -	return rc;
> +		ret = map_afu_irq(vma, vmf->address, offset, ctx);
> +	return ret;
>   }
> 
>   static const struct vm_operations_struct ocxl_vmops = {
> diff --git a/drivers/misc/ocxl/sysfs.c b/drivers/misc/ocxl/sysfs.c
> index d9753a1..0ab1fd1 100644
> --- a/drivers/misc/ocxl/sysfs.c
> +++ b/drivers/misc/ocxl/sysfs.c
> @@ -64,7 +64,7 @@ static ssize_t global_mmio_read(struct file *filp, struct kobject *kobj,
>   	return count;
>   }
> 
> -static int global_mmio_fault(struct vm_fault *vmf)
> +static vm_fault_t global_mmio_fault(struct vm_fault *vmf)
>   {
>   	struct vm_area_struct *vma = vmf->vma;
>   	struct ocxl_afu *afu = vma->vm_private_data;
> @@ -75,8 +75,7 @@ static int global_mmio_fault(struct vm_fault *vmf)
> 
>   	offset = vmf->pgoff;
>   	offset += (afu->global_mmio_start >> PAGE_SHIFT);
> -	vm_insert_pfn(vma, vmf->address, offset);
> -	return VM_FAULT_NOPAGE;
> +	return vmf_insert_pfn(vma, vmf->address, offset);
>   }
> 
>   static const struct vm_operations_struct global_mmio_vmops = {
>