On Mon, Jul 19, 2021 at 10:13:50AM -0700, Roman Gushchin wrote: > The inode switching code is not suited for dax inodes. An attempt > to switch a dax inode to a parent writeback structure (as a part > of a writeback cleanup procedure) results in a panic like this: [...] > The crash happens on an attempt to iterate over attached pagecache > pages and check the dirty flag: a dax inode's xarray contains pfn's > instead of generic struct page pointers. I wondered why this happens for DAX and not for other kinds of non-page entries in the inodes. The answer is that it's a tagged iteration, and shadow/swap entries are never tagged; only DAX entries get tagged. Acked-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
