On Sat, Mar 16, 2024 at 04:53:09PM +0800, Zhaoyang Huang wrote: > On Fri, Mar 15, 2024 at 8:46 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > > On Thu, Mar 14, 2024 at 04:39:21PM +0800, zhaoyang.huang wrote: > > > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx> > > > > > > Panic[1] reported which is caused by lruvec->list break. Fix the race > > > between folio_isolate_lru and release_pages. > > > > > > race condition: > > > release_pages could meet a non-refered folio which escaped from being > > > deleted from LRU but add to another list_head > > > > I don't think the bug is in folio_isolate_lru() but rather in its > > caller. > > > > * Context: > > * > > * (1) Must be called with an elevated refcount on the folio. This is a > > * fundamental difference from isolate_lru_folios() (which is called > > * without a stable reference). > > > > So when release_pages() runs, it must not see a refcount decremented to > > zero, because the caller of folio_isolate_lru() is supposed to hold one. > > > > Your stack trace is for the thread which is calling release_pages(), not > > the one calling folio_isolate_lru(), so I can't help you debug further. > Thanks for the comments. According to my understanding, > folio_put_testzero does the decrement before test which makes it > possible to have release_pages see refcnt equal zero and proceed > further(folio_get in folio_isolate_lru has not run yet). No, that's not possible. In the scenario below, at entry to folio_isolate_lru(), the folio has refcount 2. It has one refcount from thread 0 (because it must own one before calling folio_isolate_lru()) and it has one refcount from thread 1 (because it's about to call release_pages()). If release_pages() were not running, the folio would have refcount 3 when folio_isolate_lru() returned. > #0 folio_isolate_lru #1 release_pages > BUG_ON(!folio_refcnt) > if (folio_put_testzero()) > folio_get(folio) > if (folio_test_clear_lru())
