On 10/31/19 4:49 PM, Ira Weiny wrote: > On Wed, Oct 30, 2019 at 03:49:30PM -0700, John Hubbard wrote: ... >> +TODO: There is also a special case when the pages are DAX pages: in addition to >> +the above flags, the caller needs something like a layout lease on the >> +associated file. This is yet to be implemented. When it is implemented, it's >> +expected that the lease will be a prerequisite to setting FOLL_LONGTERM. > > For now we probably want to leave this note out until we figure out how this is > going to work. Best to say something like: > > Some pages, such as DAX pages, can't be pinned with longterm pins and will > fail. > OK, I have this wording queued up for the v2 patch: NOTE: Some pages, such as DAX pages, cannot be pinned with longterm pins. That's because DAX pages do not have a separate page cache, and so "pinning" implies locking down file system blocks, which is not (yet) supported in that way. thanks, John Hubbard NVIDIA
