Re: [PATCH]fix VM_CAN_NONLINEAR check in sys_remap_file_pages

Yan Zheng
2007-10-08T22:50:31Z

2007/10/8, Hugh Dickins <hugh@veritas.com>:
> On Mon, 8 Oct 2007, Yan Zheng wrote:
> >
> > The test for VM_CAN_NONLINEAR always fails
> Good catch indeed. Though I was puzzled how we do nonlinear at all,
> until I realized it's "The test for not VM_CAN_NONLINEAR always fails".
> It's not as serious as it appears, since code further down has been
> added more recently to simulate nonlinear on non-RAM-backed filesystems,
> instead of going the real nonlinear way; so most filesystems are now not
> required to do what VM_CAN_NONLINEAR was put in to ensure they could do.
> I'm confused as to where that leaves us: is this actually a fix that
> needs to go into 2.6.23? or will it suddenly disable a system call
> which has been silently working fine on various filesystems which did
> not add VM_CAN_NONLINEAR? could we just rip out VM_CAN_NONLINEAR?
> I hope Nick or Miklos is clearer on what the risks are.
> (Apologies for all the "not"s and "non"s here, I'm embarrassed
> after just criticizing Ingo's SCHED_NO_NO_OMIT_FRAME_POINTER!)
> Hugh

Yes, I mean "The test for not VM_CAN_NONLINEAR always fails". please
forgive my poor English.