On Sun, 13 Mar 2022 15:09:27 +0900 Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> wrote: > Hi Matthew, and Andrew, > > On Sat, Mar 12, 2022 at 7:56 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > > On Fri, Mar 11, 2022 at 08:43:57PM +0100, David Hildenbrand wrote: > > > Hi, > > > > > > playing with swapfiles on random file systems, I stumbled over the > > > following nilfs issue (and reproduced it on latest greatest > > > linux/master -- v5.17-rc7+). I did not try finding out when this > > > was introduced and I did not run into this issue on other file > > > systems I tried. > > > > It's a known bug in NILFS, and I think yours is the fifth report > > of it dating back eight months. > > The root cause of this issue is that NILFS uses two page caches > per inode, one for data blocks and another for b-tree node blocks. > > Even though __folio_end_writeback(), __folio_start_writeback(), and > __folio_mark_dirty() acquire lock for mapping->i_pages, > inode_to_wb(inode) inside them performs lockdep test for the former one > (i.e. inode->i_mapping->i_pages.xa_lock). > > So, mark_buffer_dirty(), end_page_writeback(), and set_page_writeback() > for pages in the latter NILFS specific page cache hit the LOCKDEP warning. > > I tried to find a way to resolve this, but have no good idea so far. If things are set up appropriately, inode_to_wb() should be able to test inode->i_mapping->host->i_mapping->i_pages.xa_lock and get the desired result. At least, that's the case with blockdevs. I don't know if nilfs2 sets things up that way.
