On Nov 21, 2018, at 5:35 AM, Matthew Wilcox [off-list ref] wrote:

It's probably better to be more explicit and answer Randy's question:

* If we fail to insert any page into the vma, the function will return
* immediately leaving any previously-inserted pages present.  Callers
* from the mmap handler may immediately return the error as their
* caller will destroy the vma, removing any successfully-inserted pages.
* Other callers should make their own arrangements for calling unmap_region().

That works for me as well.