On Mon, 2018-02-05 at 17:12 +0100, Miklos Szeredi wrote: > On Mon, Feb 5, 2018 at 4:50 PM, James Bottomley > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > > On Mon, 2018-02-05 at 08:40 -0500, Mimi Zohar wrote: > >> On filesystems, such as fuse or remote filesystems, that we can not > >> detect or rely on the filesystem to tell us when a file has changed, > >> always re-measure, re-appraise, and/or re-audit the file. > > > > Using the presence or absence of d_revalidate isn't definitive for > > uncacheable appraisals: all stacked filesystems have to implement > > d_revalidate just in case the underlying has it, but it doesn't mean > > their appraisals can't be cached if they're fully built on top of > > traditional filesystems (like they are in the Docker/OCI use case). I > > think the original flag approach is better. The only thing stackable > > filesystems argues for is that for them it should probably be a > > superblock flag so it can be per-mount point (depending on overlay > > composition). > > > > d_revalidate() also strikes me as wrong from the semantic point of > > view: it's about whether the path name to inode cache needs re- > > evaluating not whether the underlying inode could change arbitrarily. > > These are definitely related but not necessarily equivalent concepts. > > True. A more precise indication is whether cache pages have been > invalidated for a certain inode. Can we used that? I.e. > invalidate_inode_pages*() calls down into IMA or sets a flags or > whatever to indicate that the file contents might have changed. I don't think that works for the FUSE use case. Mimi
