On Mon, Jan 01, 2018 at 02:18:55AM -0800, Matthew Wilcox wrote: > On Sat, Dec 30, 2017 at 06:00:57PM -0500, Theodore Ts'o wrote: > > On Sat, Dec 30, 2017 at 05:40:28PM -0500, Theodore Ts'o wrote: > > > On Sat, Dec 30, 2017 at 12:44:17PM -0800, Matthew Wilcox wrote: > > > > > > > > I'm not sure I agree with this part. What if we add a new TCP lock class > > > > for connections which are used for filesystems/network block devices/...? > > > > Yes, it'll be up to each user to set the lockdep classification correctly, > > > > but that's a relatively small number of places to add annotations, > > > > and I don't see why it wouldn't work. > > > > > > I was exagerrating a bit for effect, I admit. (but only a bit). > > I feel like there's been rather too much of that recently. Can we stick > to facts as far as possible, please? > > > > It can probably be for all TCP connections that are used by kernel > > > code (as opposed to userspace-only TCP connections). But it would > > > probably have to be each and every device-mapper instance, each and > > > every block device, each and every mounted file system, each and every > > > bdi object, etc. > > > > Clarification: all TCP connections that are used by kernel code would > > need to be in their own separate lock class. All TCP connections used > > only by userspace could be in their own shared lock class. You can't > > use a one lock class for all kernel-used TCP connections, because of > > the Network Block Device mounted on a local file system which is then > > exported via NFS and squirted out yet another TCP connection problem. > > So the false positive you're concerned about is write-comes-in-over-NFS > (with socket lock held), NFS sends a write request to local filesystem, I'm confused, what lock does Ted think the NFS server is holding over NFS processing? --b.
