On 07/07/2017 10:44 PM, Mike Kravetz wrote: > On 07/07/2017 01:45 AM, Anshuman Khandual wrote: >> On 07/06/2017 09:47 PM, Mike Kravetz wrote: >>> 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. That would be redundant. Mirroring will just happen because old_size is 0 whether we mention the MREMAP_MIRROR flag or not. IMHO it should just mirror if the flag is specified irrespective of the old_size value. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
