[PATCH] ext4: silence an uninitialized variable warning

[PATCH] ext4: silence an uninitialized variable warning

[Dan Carpenter]

Smatch complains that "i" can be uninitialized if we don't enter the
loop.  I don't know if it's possible but we may as well silence this
warning.

Fixes: 8016e29f4362 ("ext4: fast commit recovery path")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 fs/ext4/mballoc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 85abbfb98cbe..9e8faf851c59 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -5167,7 +5167,7 @@ static ext4_fsblk_t ext4_mb_new_blocks_simple(handle_t *handle,
 	struct super_block *sb = ar->inode->i_sb;
 	ext4_group_t group;
 	ext4_grpblk_t blkoff;
-	int  i;
+	int i = 0;
 	ext4_fsblk_t goal, block;
 	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
 
-- 
2.28.0

Re: [PATCH] ext4: silence an uninitialized variable warning

[Theodore Y. Ts'o]

On Fri, Oct 30, 2020 at 02:46:20PM +0300, Dan Carpenter wrote:
> Smatch complains that "i" can be uninitialized if we don't enter the
> loop.  I don't know if it's possible but we may as well silence this
> warning.

Thanks, applied.

I changed the patch so that i gets initialized to sb->s_blocksize
instead of 0.  The only way the for loop could be skipped entirely,
leaving i initialized, is if the in-memory data structures, in
particular the bh->b_data for the on-disk superblock has gotten
corrupted enough that calculated value of group is >= to
ext4_get_groups_count(sb).  In that case, we want to exit immediately
without allocating a block, and if i is left to sb->s_blocksize, that
will cause the function to bail out right after the skipped for loop.

     	       		   	    - Ted