[PATCH] btrfs: Remove redundant assignment to ret

[PATCH] btrfs: Remove redundant assignment to ret

[Jiapeng Chong]

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.

Clean up the following clang-analyzer warning:

fs/btrfs/extent_io.c:5357:4: warning: Value stored to 'ret' is never
read [clang-analyzer-deadcode.DeadStores].

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
---
 fs/btrfs/extent_io.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 074a78a..cea58be 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5354,7 +5354,6 @@ int extent_fiemap(struct btrfs_inode *inode, struct fiemap_extent_info *fieinfo,
 				goto out_free;
 			if (ret)
 				flags |= FIEMAP_EXTENT_SHARED;
-			ret = 0;
 		}
 		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
 			flags |= FIEMAP_EXTENT_ENCODED;
-- 
1.8.3.1

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

[David Sterba]

On Sat, May 08, 2021 at 06:38:49PM +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.
> 
> Clean up the following clang-analyzer warning:
> 
> fs/btrfs/extent_io.c:5357:4: warning: Value stored to 'ret' is never
> read [clang-analyzer-deadcode.DeadStores].
> 
> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
> ---
>  fs/btrfs/extent_io.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 074a78a..cea58be 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -5354,7 +5354,6 @@ int extent_fiemap(struct btrfs_inode *inode, struct fiemap_extent_info *fieinfo,
>  				goto out_free;
>  			if (ret)
>  				flags |= FIEMAP_EXTENT_SHARED;
> -			ret = 0;

This leaves the scope where the value of 'ret' has been used for
something and it's reset to 0 for clarity. This is a pattern that we use
and will not change it just to silence clang analyzer.

[PATCH] btrfs: Remove redundant assignment to ret

[Jiapeng Chong]

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 <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
---
 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

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

[David Sterba]

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 <abaci@linux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
> ---
>  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.