Re: [PATCH] update ctime and mtime for mmaped write

From: Miklos Szeredi
Date: Wed Feb 21 2007 - 13:24:52 EST

> > Inspired by Peter Staubach's patch and the resulting comments.
> >
> >
> An updated version of the original patch was submitted to LKML
> yesterday... :-)

Strange coincidence :)

> > file = vma->vm_file;
> > start = vma->vm_end;
> > + mapping_update_time(file);
> > if ((flags & MS_SYNC) && file &&
> > (vma->vm_flags & VM_SHARED)) {
> > get_file(file);
> >
> It seems to me that this might lead to file times being updated for
> non-MAP_SHARED mappings.

In theory no, because the COW-ed pages become anonymous and are not
part of the original mapping any more.

> > +int set_page_dirty_mapping(struct page *page);
> >
> This aspect of the design seems intrusive to me. I didn't see a strong
> reason to introduce new versions of many of the routines just to handle
> these semantics. What motivated this part of your design? Why the new
> _mapping versions of routines?

Because there's no way to know inside the set_page_dirty() functions
if the dirtying comes from a memory mapping or from a modification
through a normal write(). And they have different semantics, for
write() the modification times are updated immediately.

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