[PATCH v4 3/6] btt: ensure that flags were also unchanged during a map_read

Vishal Verma
2017-07-26T23:37:44Z

In btt_map_read, we read the map twice to make sure that the map entry
didn't change after we added it to the read tracking table. In
anticipation of expanding the use of the error bit, also make sure that
the error and zero flags are constant across the two map reads.

Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
drivers/nvdimm/btt.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
index 8842baa..374ae62 100644
--- a/drivers/nvdimm/btt.c
+++ b/drivers/nvdimm/btt.c
@@ -1032,6 +1032,7 @@ static int btt_read_pg(struct btt *btt, struct bio_integrity_payload *bip,
*/
while (1) {
u32 new_map;
+ int new_t, new_e;

if (t_flag) {
zero_fill_data(page, off, cur_len);
@@ -1050,15 +1051,18 @@ static int btt_read_pg(struct btt *btt, struct bio_integrity_payload *bip,
*/
barrier();

- ret = btt_map_read(arena, premap, &new_map, &t_flag,
- &e_flag, NVDIMM_IO_ATOMIC);
+ ret = btt_map_read(arena, premap, &new_map, &new_t,
+ &new_e, NVDIMM_IO_ATOMIC);
if (ret)
goto out_rtt;

- if (postmap == new_map)
+ if ((postmap == new_map) && (t_flag == new_t) &&
+ (e_flag == new_e))
break;

postmap = new_map;
+ t_flag = new_t;
+ e_flag = new_e;
}

ret = btt_data_read(arena, page, off, postmap, cur_len);
--
2.9.3