Re: [PATCH v4 1/2] man/man2/mremap.2: describe multiple mapping move

[Alejandro Colomar <alx@kernel.org>]

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Hi Lorenzo,

On Mon, Aug 11, 2025 at 06:30:38AM +0100, Lorenzo Stoakes wrote:
> > > +Mappings can also simply be moved
> > > +(without any resizing)
> > > +by specifying equal
> > > +.I old_size
> > > +and
> > > +.I new_size
> > > +and using the
> > > +.B MREMAP_FIXED
> > > +flag
> > > +(see below).
> > > +Since Linux 6.17,
> > > +while
> > > +.I old_address
> > > +must reside within a mapping,
> >
> > I don't understand this.  What does it mean that old_address must reside
> > within a mapping?  It's a point, not a size, so I'm not sure I
> > understand it.
> 
> I think if it were a size it would be more confusing no?
> 
> It's an address, the address must be located within an existing memory mapping.

What I don't understand is: how could you not comply with that?  Could
you pass some old_address that is in two mappings?  Being a single
address, that would be impossible, right?

> Will replace with 'located' for clarity.
> 
> >
> > > +.I old_size
> > > +may span multiple mappings
> > > +which do not have to be
> > > +adjacent to one another when
> > > +performing a move like this.


Have a lovely day!
Alex

-- 
<https://www.alejandro-colomar.es/>

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