Miklos Szeredi wrote:

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Inspired by Peter Staubach's patch and the resulting comments.

  
      

An updated version of the original patch was submitted to LKML
yesterday...  :-)
    

Strange coincidence :)

  

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 		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.

  

I must profess to having a incomplete understanding of all of this
support, but then why would it be necessary to test VM_SHARED at
this point in msync()?

I ran into problems early on with file times being updated incorrectly
so I am a little sensitive this aspect.

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+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.

Perhaps I didn't understand what page_mapped() does, but it does seem to
have the right semantics as far as I could see.

    Thanx...

       ps

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