[lkml]   [2019]   [Feb]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA
On Mon, Feb 11, 2019 at 10:07 AM Jason Gunthorpe <> wrote:
> On Mon, Feb 11, 2019 at 09:22:58AM -0800, Dan Williams wrote:
> > I honestly don't like the idea that random subsystems can pin down
> > file blocks as a side effect of gup on the result of mmap. Recall that
> > it's not just RDMA that wants this guarantee. It seems safer to have
> > the file be in an explicit block-allocation-immutable-mode so that the
> > fallocate man page can describe this error case. Otherwise how would
> > you describe the scenarios under which FALLOC_FL_PUNCH_HOLE fails?
> I rather liked CL's version of this - ftruncate/etc is simply racing
> with a parallel pwrite - and it doesn't fail.
> But it also doesnt' trucate/create a hole. Another thread wrote to it
> right away and the 'hole' was essentially instantly reallocated. This
> is an inherent, pre-existing, race in the ftrucate/etc APIs.

If options are telling the truth with a potentially unexpected error,
or lying that operation succeeded when it will be immediately undone,
I'd choose the former.

 \ /
  Last update: 2019-02-11 19:16    [W:0.147 / U:4.024 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site