On Fri, Oct 4, 2024 at 1:01 AM Christian Brauner <[email protected]> wrote: > > On Thu, Oct 03, 2024 at 11:13:54AM GMT, Christian Brauner wrote: > > On Tue, Oct 01, 2024 at 03:52:05PM GMT, Andrii Nakryiko wrote: > > > 6cf41fcfe099 ("backing file: free directly") switched FMODE_BACKING > > > files to direct freeing as back then there were no use cases requiring > > > RCU protected access to such files. > > > > > > Now, with speculative lockless VMA-to-uprobe lookup logic, we do need to > > > have a guarantee that struct file memory is not going to be freed from > > > under us during speculative check. So add back RCU-delayed freeing > > > logic. > > > > > > We use headless kfree_rcu_mightsleep() variant, as file_free() is only > > > called for FMODE_BACKING files in might_sleep() context. > > > > > > Suggested-by: Suren Baghdasaryan <[email protected]> > > > Cc: Christian Brauner <[email protected]> > > > Cc: Amir Goldstein <[email protected]> > > > Signed-off-by: Andrii Nakryiko <[email protected]> > > > --- > > > > Reviewed-by: Christian Brauner <[email protected]> > > Fwiw, I have another patch series for files that I'm testing that will > require me to switch FMODE_BACKING to a SLAB_TYPSAFE_BY_RCU cache. That > shouldn't matter for your use-case though.
Correct, we assume SLAB_TYPESAFE_BY_RCU semantics for the common case anyways. But hopefully my change won't cause major merge conflicts with your patch set.
