linux-kernel - [PATCH] ext4: use BUG() instead of BUG

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Date:   Mon, 25 Mar 2019 14:00:25 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>
Cc:     clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Eric Whitney <enwlinux@...il.com>,
        Sean Fu <fxinrong@...il.com>, Jan Kara <jack@...e.cz>,
        Eric Biggers <ebiggers@...gle.com>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] ext4: use BUG() instead of BUG_ON(1)

BUG_ON(1) leads to bogus warnings from clang when
CONFIG_PROFILE_ANNOTATED_BRANCHES is set:

 fs/ext4/inode.c:544:4: error: variable 'retval' is used uninitialized whenever 'if' condition is false
      [-Werror,-Wsometimes-uninitialized]
                        BUG_ON(1);
                        ^~~~~~~~~
 include/asm-generic/bug.h:61:36: note: expanded from macro 'BUG_ON'
                                   ^~~~~~~~~~~~~~~~~~~
 include/linux/compiler.h:48:23: note: expanded from macro 'unlikely'
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 fs/ext4/inode.c:591:6: note: uninitialized use occurs here
        if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
            ^~~~~~
 fs/ext4/inode.c:544:4: note: remove the 'if' if its condition is always true
                        BUG_ON(1);
                        ^
 include/asm-generic/bug.h:61:32: note: expanded from macro 'BUG_ON'
                               ^
 fs/ext4/inode.c:502:12: note: initialize the variable 'retval' to silence this warning

Change it to BUG() so clang can see that this code path can never
continue.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 fs/ext4/extents_status.c | 4 ++--
 fs/ext4/inode.c          | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 2b439afafe13..023a3eb3afa3 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -711,7 +711,7 @@ static void ext4_es_insert_extent_ind_check(struct inode *inode,
 			 * We don't need to check unwritten extent because
 			 * indirect-based file doesn't have it.
 			 */
-			BUG_ON(1);
+			BUG();
 		}
 	} else if (retval == 0) {
 		if (ext4_es_is_written(es)) {
@@ -780,7 +780,7 @@ static int __es_insert_extent(struct inode *inode, struct extent_status *newes)
 			}
 			p = &(*p)->rb_right;
 		} else {
-			BUG_ON(1);
+			BUG();
 			return -EINVAL;
 		}
 	}
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b32a57bc5d5d..190f0478582a 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -541,7 +541,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
 			map->m_len = retval;
 			retval = 0;
 		} else {
-			BUG_ON(1);
+			BUG();
 		}
 #ifdef ES_AGGRESSIVE_TEST
 		ext4_map_blocks_es_recheck(handle, inode, map,
@@ -1876,7 +1876,7 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
 		else if (ext4_es_is_unwritten(&es))
 			map->m_flags |= EXT4_MAP_UNWRITTEN;
 		else
-			BUG_ON(1);
+			BUG();
 
 #ifdef ES_AGGRESSIVE_TEST
 		ext4_map_blocks_es_recheck(NULL, inode, map, &orig_map, 0);
-- 
2.20.0