> Mikulas, > > On Fri, Aug 19, 2011 at 10:12:24AM +0100, Joe Thornber wrote: > > On Thu, Aug 18, 2011 at 06:31:13PM -0400, Mikulas Patocka wrote: > > > I uploaded bufio-based block manager at > > > http://people.redhat.com/mpatocka/patches/kernel/dm-thinp-bufio/. It > > > supports locks, but it defines new functions down_write_non_owner and > > > up_write_non_owner. > > > > Thanks Mikulas, I'll try and get it merged over the next couple of days. > > I've merged and pushed this to my git repo. I checkouted the tree now (I tried all branches reported with git-branch -a), but I couldn't see bufio in any of the branches. > All the test-suite is passing. Performance is identical (though > hopefully we're a lot more scaleable now). > > I have to say I think the separation of io and locking is very elegant > now. Well done. > > I've made two small changes: > > i) I switched to using dm_bufio_new() rather than dm_bufio_read() at > the start of *write_lock_zero(). No point reading the data if we're > going to throw it away. OK, I forgot about this. > ii) We no longer hold the superblock lock for the duration of the > transaction. This means we can get rid of the nasty rwsem non-owner > patch. > > We have one outstanding issue however. Now we're using a rwsem per > block, lockdep is trying to validate there are no deadlocks. Which it > can't do, so is producing a warning. See the > > "Exception: Nested data dependencies leading to nested locking" > > section in lockdep-design.txt for more discussion of the problem. > > We need to suppress this somehow. I guess the right thing to do is > use the nesting level facility, eg call the superblock level 0, btree > roots level 1 etc. This will involve a lot of code changes however. > So for now I just want to turn off checking on those locks. I think you can't turn off lockdep just so. Those "non-owner" lock versions, bypass lockdep. Mikulas > - Joe > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
