Clang warns:
mm/zswap.c:1183:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
1183 | if (objcg && !obj_cgroup_may_zswap(objcg))
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/zswap.c:1327:9: note: uninitialized use occurs here
1327 | return ret;
| ^~~
mm/zswap.c:1183:2: note: remove the 'if' if its condition is always false
1183 | if (objcg && !obj_cgroup_may_zswap(objcg))
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1184 | goto reject;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/zswap.c:1158:9: note: initialize the variable 'ret' to silence this warning
1158 | int ret;
| ^
| = 0
1 error generated.
This condition used to return -ENOMEM by going to the shrink label, so
set ret to -ENOMEM in the if block explicitly to avoid using it
uninitialized.
Fixes: 6804144bf1cf ("zswap: do not shrink if cgroup may not zswap")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/202306011435.2BxsHFUE-lkp@xxxxxxxxx/
Closes: https://lore.kernel.org/202306012152.o4FL7Y6J-lkp@xxxxxxxxx/
Closes: https://github.com/ClangBuiltLinux/linux/issues/1861
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
---
Changes in v2:
- Change ret to -ENOMEM to match this condition's previous return value
(Yosry)
- Link to v1: https://lore.kernel.org/r/20230601-zswap-cgroup-wsometimes-uninitialized-v1-1-35debdd19293@xxxxxxxxxx
---
mm/zswap.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/zswap.c b/mm/zswap.c
index cff93643a6ab..30092d9a3b23 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -1180,8 +1180,10 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
* local cgroup limits.
*/
objcg = get_obj_cgroup_from_page(page);
- if (objcg && !obj_cgroup_may_zswap(objcg))
+ if (objcg && !obj_cgroup_may_zswap(objcg)) {
+ ret = -ENOMEM;
goto reject;
+ }
/* reclaim space if needed */
if (zswap_is_full()) {
---
base-commit: b2424568bd9b947b2698b693ff24fec63bb4b36a
change-id: 20230601-zswap-cgroup-wsometimes-uninitialized-b549ff4247ed
Best regards,
--
Nathan Chancellor <nathan@xxxxxxxxxx>
