On Wed, Mar 29, 2000 at 03:55:28AM -0700, Jeff V. Merkey wrote:
>
>
> Andi Kleen wrote:
> >
> > > This is implemented the same way it is in the FAT and NCPFS file
> > > systems. How do they write the data back when changed?
> >
> > I don't know. Unless I'm missing something (which is quite possible)
> > they don't sync.
> > Have you tested shared mappings to be functional ?
> >
>
> No, I have not. This could possibly mean that the other FS's are
Shame on me, I missed that:
int nwfs_mmap(struct file * file, struct vm_area_struct * vma)
{
struct inode *inode = file->f_dentry->d_inode;
if (vma->vm_flags & VM_SHARED) // only PAGE_COW or read-only supported now
return -EINVAL;
I guess supporting shared mappings would be useful though for a
general purpose filesystem, because more and more programs use them.
To fix it I think it is needed to implement unmap and sync
vma operations that write the data to the file.
That still has some problems over fully page cache integrated filesystems
like ext2 (user has to call msync to see updates in read/write and it is
slower), but would at least make them work.
-Andi
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