On Sun 14-02-21 11:21:02, James Bottomley wrote: > On Sun, 2021-02-14 at 10:58 +0100, David Hildenbrand wrote: > [...] > > > 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. > > OK, so let's review history. In the first two incarnations of the > patch, it was an extension of memfd_create(). The specific objection > by Kirill Shutemov was that it doesn't share any code in common with > memfd and so should be a separate system call: > > https://lore.kernel.org/linux-api/20200713105812.dnwtdhsuyj3xbh4f@box/ Thanks for the pointer. But this argument hasn't been challenged at all. It hasn't been brought up that the overlap would be considerable higher by the hugetlb/sealing support. And so far nobody has claimed those combinations as unviable. > The other objection raised offlist is that if we do use memfd_create, > then we have to add all the secret memory flags as an additional ioctl, > whereas they can be specified on open if we do a separate system call. > The container people violently objected to the ioctl because it can't > be properly analysed by seccomp and much preferred the syscall version. > > Since we're dumping the uncached variant, the ioctl problem disappears > but so does the possibility of ever adding it back if we take on the > container peoples' objection. This argues for a separate syscall > because we can add additional features and extend the API with flags > without causing anti-ioctl riots. I am sorry but I do not understand this argument. What kind of flags are we talking about and why would that be a problem with memfd_create interface? Could you be more specific please? -- Michal Hocko SUSE Labs
