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 6x3Ct+AF M/T+v4oMtz4jbPmEGebT1iuGGtr5oyhV8MsXzLROGkGiLI6nQ3WmHAG1Hg8WzMEEd3tKuSB0PRd0SQvzhqifC+YWMrujd9UIl1qZT5oARFaoq7JkdJk7qSnq+yYuWdJYd9EPkzwQRQa8x9CtRTYEINBbV4sWvAVcbyQQy700Ku0Yd61IwGlpr0edqXZAOOi328LdZ3BVkiiRCeF37pBj0hH0z6/kgB2hgSFRTIzkvWU4r4EOecdINm+0cGhCtyBYnA4RqEJs/tUs9LYTZ32NTOjeIF7CqxwYtywT1Ki7z1emL5QHIDz+dovfl8N5wTjXM2evP X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Jason Gunthorpe wrote: > On Thu, Apr 11, 2024 at 10:28:56AM -0700, Dan Williams wrote: > > Alistair Popple wrote: > > > FS DAX pages have always maintained their own page reference counts > > > without following the normal rules for page reference counting. In > > > particular pages are considered free when the refcount hits one rather > > > than zero and refcounts are not added when mapping the page. > > > > > Tracking this requires special PTE bits (PTE_DEVMAP) and a secondary > > > mechanism for allowing GUP to hold references on the page (see > > > get_dev_pagemap). However there doesn't seem to be any reason why FS > > > DAX pages need their own reference counting scheme. > > > > This is fair. However, for anyone coming in fresh to this situation > > maybe some more "how we get here" history helps. That longer story is > > here: > > > > http://lore.kernel.org/all/166579181584.2236710.17813547487183983273.stgit@dwillia2-xfh.jf.intel.com/ > > This never got merged? :( Yeah... I got hung up on the "allocation" API to take ZONE_DEVICE pages from recfount 0 to 1 and then never circled back.