On Tue 27-11-18 16:49:47, Cristopher Lameter wrote: > On Tue, 27 Nov 2018, Mike Rapoport wrote: > > > > * @page: The page to wait for. > > > * > > > * The caller should hold a reference on @page. They expect the page to > > > * become unlocked relatively soon, but do not wish to hold up migration > > > * (for example) by holding the reference while waiting for the page to > > > * come unlocked. After this function returns, the caller should not > > > * dereference @page. > > > */ > > > > How about: > > > > They expect the page to become unlocked relatively soon, but they can wait > > for the page to come unlocked without holding the reference, to allow > > other users of the @page (for example migration) to continue. > > All of this seems a bit strange and it seems unnecessary? Maybe we need a > better explanation? > > A process has no refcount on a page struct and is waiting for it to become > unlocked? Why? Should it not simply ignore that page and continue? It > cannot possibly do anything with the page since it does not hold a > refcount. So do you suggest busy waiting on the page under migration? -- Michal Hocko SUSE Labs
