On Mon, Aug 10, 2015 at 08:14:56AM -0400, Jeff Layton wrote: > On Mon, 10 Aug 2015 05:10:35 -0700 > Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > > On Mon, Aug 10, 2015 at 07:23:51AM -0400, Jeff Layton wrote: > > > I did consider a shrinker and LRU list for this. The problem there is > > > that shrinkers are triggered on memory pressure. Keeping these files > > > open after they've been idle for a long period of time would prevent > > > the kernel from handing out leases on them, so closing them after a > > > reasonable idle period seemed like the right thing to do. > > > > True. > > > > > I suppose however we could use a shrinker/LRU _and_ add a mechanism > > > that would cause the kernel to close idle nfsd_files for an inode when > > > there is an attempt to do a F_SETLEASE. That would probably work, > > > unless I'm missing other reasons that keeping unused files open might > > > be problematic. Are there any? > > > > That seems reasonable. Keepign the file open also will prevent > > unmounting the file system, although currently any NFS export already > > causes that as well. > > Yes, though that's the reason for the new ->flush hook in the sunrpc > cache code. On any export table change, we'll clean out the nfsd_file > cache to help ensure that you'll be able to unmount soon after > unexporting a filesystem. There are definitely people with scripts that try to unexport and then immediately unmount, e.g. to migrate a filesystem elsewhere. They already run into problems thanks to export caches, locks, and v4 state. A complete shutdown of nfsd is currently the only supported way to unmount. Still, I wouldn't be surprised if there are people who (possibly just out of luck) have a working setup now that will start failing after we take these additional references. Extending the unlock_* interfaces or getting Kinglong's stuff working would help. --b. > > In any case, I'll look at the shrinker/lru thing for the next respin > and see whether adding a hook into the setlease code might be > reasonable. > > Thanks for the review so far, > -- > Jeff Layton <jlayton@xxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
