Supposes cache_check runs simultaneously with an update on a different
CPU:
cache_check task doing update
^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^
1. test for CACHE_VALID 1'. set entry->data
& !CACHE_NEGATIVE
2. use entry->data 2'. set CACHE_VALID
If the two memory writes performed in step 1' and 2' appear misordered
with respect to the reads in step 1 and 2, then the caller could get
stale data at step 2 even though it saw CACHE_VALID set on the cache
entry.
Add memory barriers to prevent this.
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
fdef7aa5d4