[PATCH 06/10] btrfs: fix remap_file_pages error

[PATCH 06/10] btrfs: fix remap_file_pages error

[Miao Xie]

when we use remap_file_pages() to remap a file, remap_file_pages always return
error. It is because btrfs didn't set VM_CAN_NONLINEAR for vma.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
 fs/btrfs/file.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index d146dde..c874833 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1150,8 +1150,15 @@ static const struct vm_operations_struct btrfs_file_vm_ops = {
 
 static int btrfs_file_mmap(struct file	*filp, struct vm_area_struct *vma)
 {
-	vma->vm_ops = &btrfs_file_vm_ops;
+	struct address_space *mapping = filp->f_mapping;
+
+	if (!mapping->a_ops->readpage)
+		return -ENOEXEC;
+
 	file_accessed(filp);
+	vma->vm_ops = &btrfs_file_vm_ops;
+	vma->vm_flags |= VM_CAN_NONLINEAR;
+
 	return 0;
 }
 
-- 
1.6.5.2

Re: [PATCH 06/10] btrfs: fix remap_file_pages error

[Christoph Hellwig]

On Thu, May 20, 2010 at 03:21:50PM +0800, Miao Xie wrote:
> +	if (!mapping->a_ops->readpage)
> +		return -ENOEXEC;

I don't think there's any instance of address_space operations without
a readpage method in btrfs.

Re: [PATCH 06/10] btrfs: fix remap_file_pages error

[Miao Xie]

on 2010-5-20 16:32, Christoph Hellwig wrote:
> On Thu, May 20, 2010 at 03:21:50PM +0800, Miao Xie wrote:
>> +	if (!mapping->a_ops->readpage)
>> +		return -ENOEXEC;
> 
> I don't think there's any instance of address_space operations without
> a readpage method in btrfs.

But, Btrfs is being developing. Maybe someone implement a instance of
address_space without a readpage method in the future. So it is better
to check it, just like ext4.

Thanks