linux-kernel - [PATCH] btrfs: work around false-positive -Wsometimes-uninitialized warning

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Date:   Fri, 22 Mar 2019 15:07:47 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>
Cc:     clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Nikolay Borisov <nborisov@...e.com>,
        Lu Fengqi <lufq.fnst@...fujitsu.com>,
        Anand Jain <anand.jain@...cle.com>,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] btrfs: work around false-positive -Wsometimes-uninitialized warning

clang fails to see that the last 'else if() in btrfs_uuid_tree_add()
is always true, so 'eb' is always initialized correctly:

fs/btrfs/uuid-tree.c:129:13: error: variable 'eb' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
        } else if (ret < 0) {
                   ^~~~~~~
fs/btrfs/uuid-tree.c:139:22: note: uninitialized use occurs here
        write_extent_buffer(eb, &subid_le, offset, sizeof(subid_le));
                            ^~
fs/btrfs/uuid-tree.c:129:9: note: remove the 'if' if its condition is always true
        } else if (ret < 0) {
               ^~~~~~~~~~~~~
fs/btrfs/uuid-tree.c:90:26: note: initialize the variable 'eb' to silence this warning
        struct extent_buffer *eb;
                                ^
                                 = NULL

Change it into a plain 'else' to shut up that warning.

Link: https://bugs.llvm.org/show_bug.cgi?id=41197
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 fs/btrfs/uuid-tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/uuid-tree.c b/fs/btrfs/uuid-tree.c
index 3b2ae342e649..c1cc9a5c0024 100644
--- a/fs/btrfs/uuid-tree.c
+++ b/fs/btrfs/uuid-tree.c
@@ -126,7 +126,7 @@ int btrfs_uuid_tree_add(struct btrfs_trans_handle *trans, u8 *uuid, u8 type,
 		slot = path->slots[0];
 		offset = btrfs_item_ptr_offset(eb, slot);
 		offset += btrfs_item_size_nr(eb, slot) - sizeof(subid_le);
-	} else if (ret < 0) {
+	} else {
 		btrfs_warn(fs_info,
 			   "insert uuid item failed %d (0x%016llx, 0x%016llx) type %u!",
 			   ret, (unsigned long long)key.objectid,
-- 
2.20.0