On Wed, 6 Jul 2022 10:47:32 +0800 Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote: > > If this wakeup is not one of these, then are there reports from the > > softlockup detector? > > > > Do we have reports of processes permanently stuck in D state? > > > > No. The task is in an TASK_INTERRUPTIBLE state (see __fuse_dax_break_layouts). > The hung task reporter only reports D task (TASK_UNINTERRUPTIBLE). Thanks, I updated the changelog a bit. : FSDAX page refcounts are 1-based, rather than 0-based: if refcount is : 1, then the page is freed. The FSDAX pages can be pinned through GUP, : then they will be unpinned via unpin_user_page() using a folio variant : to put the page, however, folio variants did not consider this special : case, the result will be to miss a wakeup event (like the user of : __fuse_dax_break_layouts()). This results in a task being permanently : stuck in TASK_INTERRUPTIBLE state. : : Since FSDAX pages are only possibly obtained by GUP users, so fix GUP : instead of folio_put() to lower overhead. I believe these details are helpful for -stable maintainers who are wondering why they were sent stuff. Also for maintainers of downstreeam older kernels who are scratching heads over some user bug report, trying to find a patch which might fix it - for this they want to see a description of the user-visible effects, for matching with that bug report.
