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. Thanks, Miklos
