[PATCH RFC 0/2] Invalidate overlayfs dentries on underlying changes

[Amir Goldstein <amir73il@gmail.com>]

Miklos,Vivek,

These patches are part of the new overlay "fsnotify snapshot" series
I have been working on.

Conterary to the trend to disallow underlying offline changes with more
configurations, I have seen that some people do want to be able to make
some "careful" underlying online changes and survive [1].

In the following patches, I argue for improving the robustness of
overlayfs in the face of online underlying changes, but I have not
really proved my claims, so feel free to challenge them.

I also remember we discussed several times about the conversion of
zero return value to -ESTALE, including in the linked thread.
I did not change this behavior, but I left a boolean 'strict', which
controls this behavior. I am using this boolean to relax strict behavior
for snapshot mount later in my snapshot series. Relaxing the strict
behavior for other use cases can be considered if someone comes up with
a valid use case.

Thoughts?

Thanks,
Amir.

[1] https://lore.kernel.org/linux-unionfs/CAOQ4uxiBmFdcueorKV7zwPLCDq4DE+H8x=8H1f7+3v3zysW9qA@mail.gmail.com/

Amir Goldstein (2):
  ovl: invalidate dentry with deleted real dir
  ovl: invalidate dentry if lower was renamed

 fs/overlayfs/export.c    |  1 +
 fs/overlayfs/namei.c     |  4 +++-
 fs/overlayfs/ovl_entry.h |  2 ++
 fs/overlayfs/super.c     | 48 ++++++++++++++++++++++++++++++----------
 4 files changed, 42 insertions(+), 13 deletions(-)

-- 
2.17.1