2021-04-29 10:16:59

by Jiapeng Chong

Subject: [PATCH] btrfs: Remove redundant assignment to ret

Variable ret is set to zero but this value is never read as it
is overwritten or not used later on, hence it is a redundant
assignment and can be removed.

Cleans up the following clang-analyzer warning:

fs/btrfs/volumes.c:8019:4: warning: Value stored to 'ret' is never read
[clang-analyzer-deadcode.DeadStores].

fs/btrfs/volumes.c:4757:4: warning: Value stored to 'ret' is never read
[clang-analyzer-deadcode.DeadStores].

fs/btrfs/volumes.c:7951:4: warning: Value stored to 'ret' is never read
[clang-analyzer-deadcode.DeadStores].

Reported-by: Abaci Robot <[email protected]>
Signed-off-by: Jiapeng Chong <[email protected]>
---
fs/btrfs/volumes.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 9a1ead0..30504fa 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4754,7 +4754,6 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
mutex_unlock(&fs_info->reclaim_bgs_lock);
if (ret < 0)
goto done;
- ret = 0;
btrfs_release_path(path);
break;
}
@@ -7939,7 +7938,7 @@ int btrfs_verify_dev_extents(struct btrfs_fs_info *fs_info)
struct btrfs_key key;
u64 prev_devid = 0;
u64 prev_dev_ext_end = 0;
- int ret = 0;
+ int ret;

/*
* We don't have a dev_root because we mounted with ignorebadroots and
@@ -8016,7 +8015,6 @@ int btrfs_verify_dev_extents(struct btrfs_fs_info *fs_info)
if (ret < 0)
goto out;
if (ret > 0) {
- ret = 0;
break;
}
}
--
1.8.3.1

2021-04-29 13:00:05

by David Sterba

Subject: Re: [PATCH] btrfs: Remove redundant assignment to ret

On Thu, Apr 29, 2021 at 06:15:20PM +0800, Jiapeng Chong wrote:
> Variable ret is set to zero but this value is never read as it
> is overwritten or not used later on, hence it is a redundant
> assignment and can be removed.
>
> Cleans up the following clang-analyzer warning:

I've looked at clang analyzer warnings in the past and the dead stores
were ones of the least useful, namely because of the return value
assignments.

> fs/btrfs/volumes.c:8019:4: warning: Value stored to 'ret' is never read
> [clang-analyzer-deadcode.DeadStores].
>
> fs/btrfs/volumes.c:4757:4: warning: Value stored to 'ret' is never read
> [clang-analyzer-deadcode.DeadStores].
>
> fs/btrfs/volumes.c:7951:4: warning: Value stored to 'ret' is never read
> [clang-analyzer-deadcode.DeadStores].
>
> Reported-by: Abaci Robot <[email protected]>
> Signed-off-by: Jiapeng Chong <[email protected]>
> ---
> fs/btrfs/volumes.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 9a1ead0..30504fa 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -4754,7 +4754,6 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
> mutex_unlock(&fs_info->reclaim_bgs_lock);
> if (ret < 0)
> goto done;
> - ret = 0;
> btrfs_release_path(path);
> break;

So this is a code pattern where 'ret' is used for some local function
call but we want to make sure it does not go outside of the block as a
non-zero value, potentially being returned from the whole function.
No harm done if the value is not used later.

> }
> @@ -7939,7 +7938,7 @@ int btrfs_verify_dev_extents(struct btrfs_fs_info *fs_info)
> struct btrfs_key key;
> u64 prev_devid = 0;
> u64 prev_dev_ext_end = 0;
> - int ret = 0;
> + int ret;

Similar here, initializing ret to zero does no harm. We've had compiler
warnings about unitialized ret when some error path was jumping around
it.

>
> /*
> * We don't have a dev_root because we mounted with ignorebadroots and
> @@ -8016,7 +8015,6 @@ int btrfs_verify_dev_extents(struct btrfs_fs_info *fs_info)
> if (ret < 0)
> goto out;
> if (ret > 0) {
> - ret = 0;
> break;
> }

Same pattern as in the first case.