On Mon, 6 Jan 2025 at 19:17, Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote: > > On Mon, Jan 06, 2025 at 11:19:42AM +0100, Miklos Szeredi wrote: > > On Fri, 3 Jan 2025 at 21:31, David Hildenbrand <david@xxxxxxxxxx> wrote: > > > In any case, having movable pages be turned unmovable due to persistent > > > writaback is something that must be fixed, not worked around. Likely a > > > good topic for LSF/MM. > > > > Yes, this seems a good cross fs-mm topic. > > > > So the issue discussed here is that movable pages used for fuse > > page-cache cause a problems when memory needs to be compacted. The > > problem is either that > > > > - the page is skipped, leaving the physical memory block unmovable > > > > - the compaction is blocked for an unbounded time > > > > While the new AS_WRITEBACK_INDETERMINATE could potentially make things > > worse, the same thing happens on readahead, since the new page can be > > locked for an indeterminate amount of time, which can also block > > compaction, right? > > Yes locked pages are unmovable. How much of these locked pages/folios > can be caused by untrusted fuse server? A stuck server would quickly reach the background threshold at which point everything stops. So my guess is that accidentally this won't do much harm. Doing it deliberately (tuning max_background, starting multiple servers) the number of pages that are permanently locked could be basically unlimited. Thanks, Miklos
