On Fri, Feb 03, 2017 at 04:07:29PM +0100, Jan Kara wrote: > Some ->page_mkwrite handlers may return VM_FAULT_RETRY as its return > code (GFS2 or Lustre can definitely do this). However VM_FAULT_RETRY > from ->page_mkwrite is completely unhandled by the mm code and results > in locking and writeably mapping the page which definitely is not what > the caller wanted. Fix Lustre and block_page_mkwrite_ret() used by other > filesystems (notably GFS2) to return VM_FAULT_NOPAGE instead which > results in bailing out from the fault code, the CPU then retries the > access, and we fault again effectively doing what the handler wanted. Reading this commit message makes me wonder if this is the best fix. It would seem logical that if I want the fault to be retried that I should return VM_FAULT_RETRY, not VM_FAULT_NOPAGE. Why don't we have the MM treat VM_FAULT_RETRY the same way that it treats VM_FAULT_NOPAGE and give driver / filesystem writers one fewer way to shoot themselves in the foot?
