dm-cache's passthrough mode, introduced in kernel v3.13 commit
2ee57d587357 ("dm cache: add passthrough mode"), is a maintenance
mode that bypasses the cache, designed for scenarios where the cache
coherency is uncertain. It allows administrators to verify cache
coherency while the cached device remains operational, without having
to drop the entire cache.
In kernel v4.12, the significant dm-cache rework commit b29d4986d0da
("dm cache: significant rework to leverage dm-bio-prison-v2") caused
multiple regressions that broke passthrough mode when handling writes,
causing null-ptr-deref and coherency issues. The fixes restore
passthrough mode to full functionality.
Ming-Hung Tsai (7):
dm cache: fix null-deref with concurrent writes in passthrough mode
dm cache: fix write path cache coherency in passthrough mode
dm cache: fix write hang in passthrough mode
dm cache policy smq: fix missing locks in invalidating cache blocks
dm cache: fix concurrent write failure in passthrough mode
dm cache: fix dirty mapping checking in passthrough mode switching
dm cache: prevent entering passthrough mode after unclean shutdown
drivers/md/dm-cache-metadata.c | 20 ++++---
drivers/md/dm-cache-metadata.h | 10 ++--
drivers/md/dm-cache-policy-smq.c | 4 ++
drivers/md/dm-cache-target.c | 90 +++++++++++++++++++++++---------
4 files changed, 83 insertions(+), 41 deletions(-)
--
2.49.0
