On Tue, Mar 26, 2024 at 05:06:55PM +0800, Zhaoyang Huang wrote: > 1. Thread_readahead remove the folio from page cache and drop 2 refcnt > by readahead_folio & filemap_remove_folio(get rid of the folios which > failed to launch IO during readahead) > refcnt == 0, PG_lru == true, PG_lock == true > read_pages > ... > folio = readahead_folio > <one refcnt dropped here> > ********For the folio which can not launch IO, we should NOT drop > refcnt here??? replaced by __readahead_folio???********** > folio_get > filemap_remove_folio(folio) > folio_unlock > <one refcnt dropped here> > folio_put Ignoring any other thread, you're basically saying that there's a refcount imbalance here. Which means we'd hit an assert (that folio refcount went below zero) in the normal case where another thread wasn't simultaneously trying to do anything.
