linux-kernel - Re: [PATCH 01/10] cramfs: Convert to use vmf_insert

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Date:   Tue, 28 Aug 2018 13:49:25 -0400 (EDT)
From:   Nicolas Pitre <nicolas.pitre@...aro.org>
To:     Matthew Wilcox <willy@...radead.org>
cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Souptick Joarder <jrdr.linux@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/10] cramfs: Convert to use vmf_insert_mixed

On Tue, 28 Aug 2018, Matthew Wilcox wrote:

> cramfs is the only remaining user of vm_insert_mixed; convert it.
> 
> Signed-off-by: Matthew Wilcox <willy@...radead.org>
> ---
>  fs/cramfs/inode.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> index f408994fc632..b72449c19cd1 100644
> --- a/fs/cramfs/inode.c
> +++ b/fs/cramfs/inode.c
> @@ -417,10 +417,15 @@ static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
>  		 */
>  		int i;
>  		vma->vm_flags |= VM_MIXEDMAP;
> -		for (i = 0; i < pages && !ret; i++) {
> +		for (i = 0; i < pages; i++) {
> +			vm_fault_t vmf;
>  			unsigned long off = i * PAGE_SIZE;
>  			pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
> -			ret = vm_insert_mixed(vma, vma->vm_start + off, pfn);
> +			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
> +			if (vmf & VM_FAULT_ERROR) {
> +				pages = i;
> +				break;
> +			}

I'd suggest this to properly deal with errers instead:

diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index f408994fc6..0c35e62f10 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -418,9 +418,12 @@ static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
 		int i;
 		vma->vm_flags |= VM_MIXEDMAP;
 		for (i = 0; i < pages && !ret; i++) {
+			vm_fault_t vmf;
 			unsigned long off = i * PAGE_SIZE;
 			pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
-			ret = vm_insert_mixed(vma, vma->vm_start + off, pfn);
+			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
+			if (vmf & VM_FAULT_ERROR)
+				ret = vm_fault_to_errno(vmf, 0);
 		}
 	}
 

Nicolas