On Thu, 13 Jan 2011, Miklos Szeredi wrote: > On Sat, 8 Jan 2011, Nick Piggin wrote: > > The vfs-scale branch is now upstream. If you haven't > > looked yet, your filesystem is likely to have been > > touched, so check it out. > > > > Also look at Documentation/filesystems/porting and > > path-lookup.txt. > > > > The dcache_lock stuff should have been all done for you > > (for in-tree filesystems, I can help out of tree fses with > > conversions there if you ping me offline). > > > > The rcu-walk stuff can be more tricky for your filesystem > > to take advantage of. > > > > If you supply a .d_revalidate, .permission, or .check_acl, > > then path walking is going to be slow and unscalable for > > you. > > > > Out of tree filesystems: you _have_ to at least add a line > > of code to the above functions in order to specify that > > you don't want to participate in rcu-walk. > > > > Otherwise, you don't have to care about rcu-walk if you > > have a legacy or special filesystem like configfs then I'd > > advise against anything fancy. But if you have a > > userbase and you expect them to actually do any path > > lookups into your filesystem, please take a look. > > One other thing: I know ECHILD is safe since no sane filesystem will > return it in its permission or revalidate callbacks, and even if it > does that's just a loss of optimization. And it's not entirely safe either. A fuse filesystem returning ECHILD would make nameidata_dentry_drop_rcu() to BUG. So some sort of errno filter is necessary in the fuse kernel module. Thanks, Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
