On Tue, Jun 11, 2024 at 03:13:45PM +0200, Mateusz Guzik wrote: > On Tue, Jun 11, 2024 at 3:04 PM Christian Brauner <brauner@xxxxxxxxxx> wrote: > > > > On Tue, Jun 11, 2024 at 01:40:37PM +0200, Mateusz Guzik wrote: > > > On Tue, Jun 11, 2024 at 12:50:11PM +0200, Jan Kara wrote: > > > > On Tue 11-06-24 12:16:31, Mateusz Guzik wrote: > > > > > +/** > > > > > + * ilookup5 - search for an inode in the inode cache > > > > ^^^ ilookup5_rcu > > > > > > > > > > fixed in my branch > > > > > > > > + * @sb: super block of file system to search > > > > > + * @hashval: hash value (usually inode number) to search for > > > > > + * @test: callback used for comparisons between inodes > > > > > + * @data: opaque data pointer to pass to @test > > > > > + * > > > > > + * This is equivalent to ilookup5, except the @test callback must > > > > > + * tolerate the inode not being stable, including being mid-teardown. > > > > > + */ > > > > ... > > > > > +struct inode *ilookup5_nowait_rcu(struct super_block *sb, unsigned long hashval, > > > > > + int (*test)(struct inode *, void *), void *data); > > > > > > > > I'd prefer wrapping the above so that it fits into 80 columns. > > > > > > > > > > the last comma is precisely at 80, but i can wrap it if you insist > > > > > > > Otherwise feel free to add: > > > > > > > > Reviewed-by: Jan Kara <jack@xxxxxxx> > > > > > > > > > > thanks > > > > > > I'm going to wait for more feedback, tweak the commit message to stress > > > that this goes from 2 hash lock acquires to 1, maybe fix some typos and > > > submit a v4. > > > > > > past that if people want something faster they are welcome to implement > > > or carry it over the finish line themselves. > > > > I'm generally fine with this but I would think that we shouldn't add all > > these helpers without any users. I'm not trying to make this a chicken > > and egg problem though. Let's get the blessing from Josef to convert > > btrfs to that *_rcu variant and then we can add that helper. Additional > > helpers can follow as needed? @Jan, thoughts? > > That's basically v1 of the patch (modulo other changes like EXPORT_SYMBOL_GPL). > > It only has iget5_locked_rcu for btrfs and ilookup5_rcu for bcachefs, > which has since turned out to not use it. > > Jan wanted iget5_locked_rcu to follow the iget5_locked in style, hence > I ended up with 3 helpers instead of 1. We don't need any extra APIs if you just convert the inode cache to using hash-bl rather than just converting lookups to RCU. Everyone automatically gets the all extra scalability improvements and no new interfaces are needed at all. -Dave. -- Dave Chinner david@xxxxxxxxxxxxx
