2022-07-22 16:50:24

by Nathan Chancellor

Subject: [PATCH] btrfs: Fix unused variable in load_free_space_cache()

When CONFIG_LOCKDEP is unset, there is a warning about the mapping
variable being unused:

fs/btrfs/free-space-cache.c:929:24: warning: variable 'mapping' set but not used [-Wunused-but-set-variable]
struct address_space *mapping;
^
1 warning generated.

lockdep_set_class() does not do anything with the first parameter to the
macro when CONFIG_LOCKDEP is not set so just eliminate the mapping
variable and use inode instead, which is always used in the function.

Fixes: 22d85ab1af7d ("btrfs: Change the lockdep class of struct inode's invalidate_lock")
Link: https://github.com/ClangBuiltLinux/linux/issues/1672
Signed-off-by: Nathan Chancellor <[email protected]>
---
fs/btrfs/free-space-cache.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index a2b2329ae558..e8fce6b19559 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -926,7 +926,6 @@ int load_free_space_cache(struct btrfs_block_group *block_group)
int ret = 0;
bool matched;
u64 used = block_group->used;
- struct address_space *mapping;

/*
* Because we could potentially discard our loaded free space, we want
@@ -991,8 +990,8 @@ int load_free_space_cache(struct btrfs_block_group *block_group)
* space inodes to prevent false positives related to locks for normal
* inodes.
*/
- mapping = &inode->i_data;
- lockdep_set_class(&mapping->invalidate_lock, &btrfs_free_space_inode_key);
+ lockdep_set_class(&inode->i_data.invalidate_lock,
+ &btrfs_free_space_inode_key);

ret = __load_free_space_cache(fs_info->tree_root, inode, &tmp_ctl,
path, block_group->start);

base-commit: ba37a9d53d71f94ed78f2e53d84be7fa77e2a2b3
--
2.37.1

2022-07-25 16:46:11

by David Sterba

Subject: Re: [PATCH] btrfs: Fix unused variable in load_free_space_cache()

On Fri, Jul 22, 2022 at 09:38:54AM -0700, Nathan Chancellor wrote:
> When CONFIG_LOCKDEP is unset, there is a warning about the mapping
> variable being unused:
>
> fs/btrfs/free-space-cache.c:929:24: warning: variable 'mapping' set but not used [-Wunused-but-set-variable]
> struct address_space *mapping;
> ^
> 1 warning generated.
>
> lockdep_set_class() does not do anything with the first parameter to the
> macro when CONFIG_LOCKDEP is not set so just eliminate the mapping
> variable and use inode instead, which is always used in the function.
>
> Fixes: 22d85ab1af7d ("btrfs: Change the lockdep class of struct inode's invalidate_lock")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1672
> Signed-off-by: Nathan Chancellor <[email protected]>

Folded to the patch, thanks.