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

[Peter Staubach]

Miklos Szeredi wrote:
> > > > Why is the flag checked in __fput()?
> > > >     
> > > >         
> > > It's because of this bit in the standard:
> > >
> > >     If there is no such call and if the underlying file is modified
> > >     as a result of a write reference, then these fields shall be
> > >     marked for update at some time after the write reference.
> > >
> > > It could be done in munmap/mremap, but it seemed more difficult to
> > > track down all the places where the vma is removed.  But yes, that may
> > > be a nicer solution.
> > >       
> > It seems to me that, with this support, a file, which is mmap'd,
> > modified, but never msync'd or munmap'd, will never get its mtime
> > updated.  Or did I miss that?
> >
> > I also don't see how an mmap'd block device will get its mtime
> > updated either.
> >     
>
> __fput() will be called when there are no more references to 'file',
> then it will update the time if the flag is set.  This applies to
> regular files as well as devices.
>
>   

I suspect that you will find that, for a block device, the wrong inode
gets updated.  That's where the bd_inode_update_time() portion of my
proposed patch came from.

> But I've moved the check from __fput to remove_vma() in the next
> revision of the patch, which would give slightly nicer semantics, and
> be equally conforming.

This still does not address the situation where a file is 'permanently'
mmap'd, does it?

   Thanx...

      ps
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