fuse: invalidate readdir cache on epoch bump

FUSE_NOTIFY_INC_EPOCH invalidates dentries, but does not invalidate cached
readdir results. A process with cwd inside a FUSE mount can therefore
observe stale readdir(".") output after an epoch bump.

Fix this by recording epoch in the readdir cache and checking it on reuse.

Minimal reproducer:

- mount a tiny FUSE fs with an empty root directory
- on opendir, enable fi->cache_readdir and fi->keep_cache
- chdir into the mount and call readdir(".") to populate readdir cache
- make the FUSE server report one file in the root directory
- send only FUSE_NOTIFY_INC_EPOCH
- call readdir(".") again; before this change it stays stale, after this
  change it sees the new file

Fixes: 2396356a945b ("fuse: add more control over cache invalidation behaviour")
Signed-off-by: Jun Wu <quark@meta.com>
Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Luis Henriques <luis@igalia.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

0 files changed, 0 insertions, 0 deletions