Enabling FUSE passthrough for mmap-ed operations not only affects
performance, but has also been shown as mandatory for the correct
functioning of FUSE passthrough.
yanwu noticed [1] that a FUSE file with passthrough enabled may suffer
data inconsistencies if the same file is also accessed with mmap. What
happens is that read/write operations are directly applied to the lower
file system (and its cache), while mmap-ed operations are affecting the
FUSE cache.
Extend the FUSE passthrough implementation to also handle memory-mapped
FUSE file, to both fix the cache inconsistencies and extend the
passthrough performance benefits to mmap-ed operations.
[1] https://lore.kernel.org/lkml/20210119110654.11817-1-wu-yan@tcl.com/
Bug: 168023149
Link: https://lore.kernel.org/lkml/20210125153057.3623715-9-balsini@android.com/
Signed-off-by: Alessio Balsini <balsini@android.com>
Change-Id: Ifad4698b0380f6e004c487940ac6907b9a9f2964
Signed-off-by: Alessio Balsini <balsini@google.com>
5f339265fd