Re: [RFC PATCH 1/1] mm/mremap: add MREMAP_MIRROR flag for existing mirroring functionality

On 07/07/2017 01:45 AM, Anshuman Khandual wrote:

On 07/06/2017 09:47 PM, Mike Kravetz wrote:

quoted

The mremap system call has the ability to 'mirror' parts of an existing
mapping.  To do so, it creates a new mapping that maps the same pages as
the original mapping, just at a different virtual address.  This
functionality has existed since at least the 2.6 kernel.

This patch simply adds a new flag to mremap which will make this
functionality part of the API.  It maintains backward compatibility with
the existing way of requesting mirroring (old_size == 0).

If this new MREMAP_MIRROR flag is specified, then new_size must equal
old_size.  In addition, the MREMAP_MAYMOVE flag must be specified.

Yeah it all looks good. But why is this requirement that if
MREMAP_MAYMOVE is specified then old_size and new_size must
be equal.

No real reason.  I just wanted to clearly separate the new interface from
the old.  On second thought, it would be better to require old_size == 0
as in the legacy interface.

-- 
Mike Kravetz

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>