On Thu, Mar 02, 2017 at 01:45:35PM +0900, byungchul.park wrote: > From: Matthew Wilcox [mailto:willy@xxxxxxxxxxxxx] > > On Tue, Feb 28, 2017 at 07:15:47PM +0100, Peter Zijlstra wrote: > > > (And we should not be returning to userspace with locks held anyway -- > > > lockdep already has a check for that). > > > > Don't we return to userspace with page locks held, eg during async > > directio? > > Hello, > > I think that the check when returning to user with crosslocks held > should be an exception. Don't you think so? Oh yes. We have to keep the pages locked during reads, and we have to return to userspace before I/O is complete, therefore we have to return to userspace with pages locked. They'll be unlocked by the interrupt handler in page_endio(). Speaking of which ... this feature is far too heavy for use in production on pages. You're almost trebling the size of struct page. Can we do something like make all struct pages share the same lockdep_map? We'd have to not complain about holding one crossdep lock and acquiring another one of the same type, but with millions of pages in the system, it must surely be creating a gargantuan graph right now? -- 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>
