linux-kernel - [PATCH] f2fs: Fix type of single bit bitfield in f2fs_io

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Date:   Wed, 01 Feb 2023 09:40:22 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     jaegeuk@...nel.org, chao@...nel.org
Cc:     ndesaulniers@...gle.com, trix@...hat.com,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        patches@...ts.linux.dev, kernel test robot <lkp@...el.com>,
        Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH] f2fs: Fix type of single bit bitfield in f2fs_io_info

Clang warns:

  ../fs/f2fs/data.c:995:17: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion]
          fio->submitted = 1;
                         ^ ~
  ../fs/f2fs/data.c:1011:15: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion]
                          fio->retry = 1;
                                     ^ ~

  ../fs/f2fs/segment.c:3320:16: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion]
                  fio->in_list = 1;
                               ^ ~

There is not a bug here because the value of these fields is never
explicitly compared against (just whether it is zero or non-zero) but
it is easy to silence the warning by using an unsigned type to allow
an assignment of 0 or 1 without implicit conversion.

Fixes: 998863dadd2c ("f2fs: reduce stack memory cost by using bitfield in struct f2fs_io_info")
Link: https://github.com/ClangBuiltLinux/linux/issues/1796
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 fs/f2fs/f2fs.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 08dc64c5050e..89f6fdfeed19 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1213,12 +1213,12 @@ struct f2fs_io_info {
 	int compr_blocks;	/* # of compressed block addresses */
 	int need_lock:8;	/* indicate we need to lock cp_rwsem */
 	int version:8;		/* version of the node */
-	int submitted:1;	/* indicate IO submission */
-	int in_list:1;		/* indicate fio is in io_list */
-	int is_por:1;		/* indicate IO is from recovery or not */
-	int retry:1;		/* need to reallocate block address */
-	int encrypted:1;	/* indicate file is encrypted */
-	int post_read:1;	/* require post read */
+	unsigned int submitted:1;	/* indicate IO submission */
+	unsigned int in_list:1;		/* indicate fio is in io_list */
+	unsigned int is_por:1;		/* indicate IO is from recovery or not */
+	unsigned int retry:1;		/* need to reallocate block address */
+	unsigned int encrypted:1;	/* indicate file is encrypted */
+	unsigned int post_read:1;	/* require post read */
 	enum iostat_type io_type;	/* io type */
 	struct writeback_control *io_wbc; /* writeback control */
 	struct bio **bio;		/* bio for ipu */

---
base-commit: de6b3a5e09b29c014bd04044b023896107cfa2ee
change-id: 20230201-f2fs-fix-single-length-bitfields-df8cc78e880a

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