> Am 14.02.2021 um 10:20 schrieb Mike Rapoport <rppt@xxxxxxxxxx>: > > On Fri, Feb 12, 2021 at 10:18:19AM +0100, David Hildenbrand wrote: >>> On 12.02.21 00:09, Mike Rapoport wrote: >>> On Thu, Feb 11, 2021 at 01:07:10PM +0100, David Hildenbrand wrote: >>>> On 11.02.21 12:27, Mike Rapoport wrote: >>>>> On Thu, Feb 11, 2021 at 10:01:32AM +0100, David Hildenbrand wrote: >>>> >>>> So let's talk about the main user-visible differences to other memfd files >>>> (especially, other purely virtual files like hugetlbfs). With secretmem: >>>> >>>> - File content can only be read/written via memory mappings. >>>> - File content cannot be swapped out. >>>> >>>> I think there are still valid ways to modify file content using syscalls: >>>> e.g., fallocate(PUNCH_HOLE). Things like truncate also seems to work just >>>> fine. >>> These work perfectly with any file, so maybe we should have added >>> memfd_create as a flag to open(2) back then and now the secretmem file >>> descriptors? >> >> I think open() vs memfd_create() makes sense: for open, the path specifies >> main properties (tmpfs, hugetlbfs, filesystem). On memfd, there is no such >> path and the "type" has to be specified differently. >> >> Also, open() might open existing files - memfd always creates new files. > > Yes, but still open() returns a handle to a file and memfd_create() returns > a handle to a file. The differences may be well hidden by e.g. O_MEMORY and > than features unique to memfd files will have their set of O_SOMETHING > flags. > Let‘s agree to disagree. > It's the same logic that says "we already have an interface that's close > enough and it's fine to add a bunch of new flags there". No, not quite. But let‘s agree to disagree. > > And here we come to the question "what are the differences that justify a > new system call?" and the answer to this is very subjective. And as such we > can continue bikeshedding forever. I think this fits into the existing memfd_create() syscall just fine, and I heard no compelling argument why it shouldn‘t. That‘s all I can say.
