On Tue 09-04-13 14:04:32, Andrew Morton wrote: > On Tue, 9 Apr 2013 11:06:17 -0700 "Darrick J. Wong" <darrick.wong@xxxxxxxxxx> wrote: > > > + * Here we write back pagecache data that may be mmaped. Since > > + * we cannot afford to clean the page and set PageWriteback > > + * here due to lock ordering (page lock ranks above transaction > > + * start), the data can change while IO is in flight. Tell the > > + * block layer it should bounce the bio pages if stable data > > + * during write is required. > > I think there are already ab/ba deadlocks between lock_page() and > journal_start(). iirc one path was write(), I forget which was the > other path. This was 10+ years ago and nobody else noticed and I > didn't know how to fix it so I didn't tell anyone ;) Hum, I don't think they are there anymore ;) > It would be neat to be able to hook things like journal_start() into > lockdep but I don't think that lockdep has easy provision for wiring > oddball things into its mechanisms. Actually if you look at fs/jbd/transaction.c:start_this_handle(), you will notice that it is wired into lockdep (the lock_map_acquire() call there). And it works since I've seen quite some reports from it ;) Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>