linux-kernel - [PATCH] dm flakey: Fix clang -Wparentheses-equality in flakey

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Date:   Thu, 02 Feb 2023 09:58:18 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     agk@...hat.com, snitzer@...nel.org
Cc:     ndesaulniers@...gle.com, trix@...hat.com,
        sweettea-kernel@...miny.me, mpatocka@...hat.com,
        dm-devel@...hat.com, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, patches@...ts.linux.dev,
        Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH] dm flakey: Fix clang -Wparentheses-equality in
 flakey_map()

Clang warns:

  ../drivers/md/dm-flakey.c:369:28: error: equality comparison with extraneous parentheses [-Werror,-Wparentheses-equality]
                          if ((fc->corrupt_bio_rw == WRITE)) {
                               ~~~~~~~~~~~~~~~~~~~^~~~~~~~
  ../drivers/md/dm-flakey.c:369:28: note: remove extraneous parentheses around the comparison to silence this warning
                          if ((fc->corrupt_bio_rw == WRITE)) {
                              ~                   ^       ~
  ../drivers/md/dm-flakey.c:369:28: note: use '=' to turn this equality comparison into an assignment
                          if ((fc->corrupt_bio_rw == WRITE)) {
                                                  ^~
                                                  =
  1 error generated.

GCC only warns when one set of parentheses are used for assignment
expressions, whereas clang additionally warns when two sets of
parentheses are used for equality comparisons. Remove the extra set of
parentheses to silence the warning as it suggests, as this is obviously
supposed to be an equality comparison.

Fixes: 0e766389cedc ("dm flakey: fix logic when corrupting a bio")
Link: https://github.com/ClangBuiltLinux/linux/issues/1798
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
I do not mind this change being squashed with the offending commit, as I
noticed it was Cc'd for stable, which would minimize the chance for
breakage.
---
 drivers/md/dm-flakey.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index 08f9aa476d97..335684a1aeaa 100644
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -366,7 +366,7 @@ static int flakey_map(struct dm_target *ti, struct bio *bio)
 		 * Corrupt matching writes.
 		 */
 		if (fc->corrupt_bio_byte) {
-			if ((fc->corrupt_bio_rw == WRITE)) {
+			if (fc->corrupt_bio_rw == WRITE) {
 				if (all_corrupt_bio_flags_match(bio, fc))
 					corrupt_bio_data(bio, fc);
 			}

---
base-commit: 6f30cc248507ee96c22ff4c3cbc86099ff12b7a9
change-id: 20230202-dm-parenthesis-warning-6139f4b5020b

Best regards,
-- 
Nathan Chancellor <nathan@...nel.org>