On Tue, Jul 12, 2022 at 9:05 AM Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > On Mon, 11 Jul 2022 at 22:11, Paul Moore <paul@xxxxxxxxxxxxxx> wrote: > > On Fri, Jul 1, 2022 at 10:15 AM Paul Moore <paul@xxxxxxxxxxxxxx> wrote: > > > On Fri, Jul 1, 2022 at 10:11 AM Paul Moore <paul@xxxxxxxxxxxxxx> wrote: > > > > > > > > If an old readdir cache entry is found during lookup we need to > > > > ensure that we drop a reference to the old cache entry before > > > > we remove it from the cache. > > > > > > > > Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx> > > > > --- > > > > fs/overlayfs/readdir.c | 21 +++++++++++---------- > > > > 1 file changed, 11 insertions(+), 10 deletions(-) > > > > > > I ran across this a few months ago while working on something related > > > in overlayfs' readdir cache, unfortunately that work has been shelved > > > for now, but it seems like this bugfix might still have merit, > > > although I'll leave that decision up to the overlayfs experts; it's > > > very possible I've missed an important detail and this isn't actually > > > a bug. > > > > > > I've done some basic manual testing (kernel boots, > > > mounting/traversal/accesses are all okay), but nothing exhaustive. > > > > Based on the lack of a response, should I assume this is not a bug and > > this patch is not needed? > > Hi Paul, > > Sorry for the late response. > > Yes, the code is okay, though could be better documented. The logic > is that only open directories contain counted references to the cache, > not the directory inode. The uncounted reference from the inode is > used to allow sharing the cache in case there are mulitple directory > readers. Thus the ref from the inode can be dropped without > decrementing the count, and this reference is reset to NULL when the > count hits zero. Locking is provided by i_rwsem. Great, I'm glad to hear the existing code is working as intended. Thanks for the explanation too! -- paul-moore.com
