If we have an overlay file whose corresponding Dirent is frozen, then we should
not bother calling Readdir on the upper or lower files, since DirentReaddir
will calculate children based on the frozen Dirent tree.
A test was added that fails without this change.
PiperOrigin-RevId: 213531215
Change-Id: I4d6c98f1416541a476a34418f664ba58f936a81d
In the general case with an overlay, all mmap calls must go through the
overlay, because in the event of a copy-up, the overlay needs to invalidate any
previously-created mappings.
If there if no lower file, however, there will never be a copy-up, so the
overlay can delegate directly to the upper file in that case.
This also allows us to correctly mmap /dev/zero when it is in an overlay. This
file has special semantics which the overlay does not know about. In
particular, it does not implement Mappable(), which (in the general case) the
overlay uses to detect if a file is mappable or not.
PiperOrigin-RevId: 205306743
Change-Id: I92331649aa648340ef6e65411c2b42c12fa69631
Ian Gudger
Nicolas Lacasse
Zhaozhong Ni
Michael Pratt
Googler