Re: [patch] mremap.2: Add description of old_size == 0 functionality

On Tue 19-09-17 14:11:19, Florian Weimer wrote:

On 09/18/2017 07:11 PM, Mike Kravetz wrote:

[...]

quoted

I can drop this wording, but would still like to suggest memfd_create as
the preferred method of creating duplicate mappings.  It would be good if
others on Cc: could comment as well.

mremap seems to work with non-anonymous mappings, too:

only for shared mappings in fact. Because once we have CoW then mremap
will not provide you with the same content as the original mapping.

[...]

quoted

Just curious, does glibc make use of this today?  Or, is this just something
that you think may be useful.

To my knowledge, we do not use this today.  But it certainly looks very
useful.

What would be the usecase. I mean why don't you simply create a new
mapping by a plain mmap when you have no guarantee about the same
content?
-- 
Michal Hocko
SUSE Labs