4.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
commit 546eb0317cfa3c4f9e1d9ab892766d65d7f78fad upstream.
This commit:
5fdf8e5ba566 ("libnvdimm: re-enable deep flush for pmem devices via fsync()")
intended to make sure that deep flush was always available even on
platforms which support a power-fail protected CPU cache. An unintended
side effect of this change was that we also lost the ability to skip
flushing CPU caches on those power-fail protected CPU cache.
Fix this by skipping the low level cache flushing in dax_flush() if we have
CPU caches which are power-fail protected. The user can still override this
behavior by manually setting the write_cache state of a namespace. See
libndctl's ndctl_namespace_write_cache_is_enabled(),
ndctl_namespace_enable_write_cache() and
ndctl_namespace_disable_write_cache() functions.
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 5fdf8e5ba566 ("libnvdimm: re-enable deep flush for pmem devices via fsync()")
Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/nvdimm/region_devs.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1132,7 +1132,8 @@ EXPORT_SYMBOL_GPL(nvdimm_has_flush);
int nvdimm_has_cache(struct nd_region *nd_region)
{
- return is_nd_pmem(&nd_region->dev);
+ return is_nd_pmem(&nd_region->dev) &&
+ !test_bit(ND_REGION_PERSIST_CACHE, &nd_region->flags);
}
EXPORT_SYMBOL_GPL(nvdimm_has_cache);
