On 1.10.19 г. 20:57 ч., David Sterba wrote:
> The attribute is more relaxed than const and the functions could
> dereference pointers, as long as the observable state is not changed. We
> do have such functions, based on -Wsuggest-attribute=pure .
>
> The visible effects of this patch are negligible, there are differences
> in the assembly but hard to summarize.
>
> Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
one remark: I'm not sure the attribute needs to be duplicated in the
declaration and definition.
> ---
> fs/btrfs/async-thread.c | 6 ++----
> fs/btrfs/async-thread.h | 4 ++--
> fs/btrfs/ctree.c | 2 +-
> fs/btrfs/ctree.h | 4 ++--
> fs/btrfs/dev-replace.c | 2 +-
> fs/btrfs/dev-replace.h | 2 +-
> fs/btrfs/ioctl.c | 2 +-
> fs/btrfs/space-info.c | 2 +-
> fs/btrfs/space-info.h | 2 +-
> 9 files changed, 12 insertions(+), 14 deletions(-)
>
> diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
> index b97ae1b03417..1d32a07bb2d1 100644
> --- a/fs/btrfs/async-thread.c
> +++ b/fs/btrfs/async-thread.c
> @@ -53,14 +53,12 @@ struct btrfs_workqueue {
> struct __btrfs_workqueue *high;
> };
>
> -struct btrfs_fs_info *
> -btrfs_workqueue_owner(const struct __btrfs_workqueue *wq)
> +struct btrfs_fs_info * __pure btrfs_workqueue_owner(const struct __btrfs_workqueue *wq)
> {
> return wq->fs_info;
> }
>
> -struct btrfs_fs_info *
> -btrfs_work_owner(const struct btrfs_work *work)
> +struct btrfs_fs_info * __pure btrfs_work_owner(const struct btrfs_work *work)
> {
> return work->wq->fs_info;
> }
> diff --git a/fs/btrfs/async-thread.h b/fs/btrfs/async-thread.h
> index c5bf2b117c05..a4434301d84d 100644
> --- a/fs/btrfs/async-thread.h
> +++ b/fs/btrfs/async-thread.h
> @@ -41,8 +41,8 @@ void btrfs_queue_work(struct btrfs_workqueue *wq,
> void btrfs_destroy_workqueue(struct btrfs_workqueue *wq);
> void btrfs_workqueue_set_max(struct btrfs_workqueue *wq, int max);
> void btrfs_set_work_high_priority(struct btrfs_work *work);
> -struct btrfs_fs_info *btrfs_work_owner(const struct btrfs_work *work);
> -struct btrfs_fs_info *btrfs_workqueue_owner(const struct __btrfs_workqueue *wq);
> +struct btrfs_fs_info * __pure btrfs_work_owner(const struct btrfs_work *work);
> +struct btrfs_fs_info * __pure btrfs_workqueue_owner(const struct __btrfs_workqueue *wq);
> bool btrfs_workqueue_normal_congested(const struct btrfs_workqueue *wq);
>
> #endif
> diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> index f2f9cf1149a4..3a4d8e27e565 100644
> --- a/fs/btrfs/ctree.c
> +++ b/fs/btrfs/ctree.c
> @@ -1538,7 +1538,7 @@ static int comp_keys(const struct btrfs_disk_key *disk,
> /*
> * same as comp_keys only with two btrfs_key's
> */
> -int btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_key *k2)
> +int __pure btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_key *k2)
> {
> if (k1->objectid > k2->objectid)
> return 1;
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 793085770c84..df0f2de69991 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -2511,7 +2511,7 @@ void btrfs_wait_for_snapshot_creation(struct btrfs_root *root);
> /* ctree.c */
> int btrfs_bin_search(struct extent_buffer *eb, const struct btrfs_key *key,
> int level, int *slot);
> -int btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_key *k2);
> +int __pure btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_key *k2);
> int btrfs_previous_item(struct btrfs_root *root,
> struct btrfs_path *path, u64 min_objectid,
> int type);
> @@ -2912,7 +2912,7 @@ long btrfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
> long btrfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
> int btrfs_ioctl_get_supported_features(void __user *arg);
> void btrfs_sync_inode_flags_to_i_flags(struct inode *inode);
> -int btrfs_is_empty_uuid(u8 *uuid);
> +int __pure btrfs_is_empty_uuid(u8 *uuid);
> int btrfs_defrag_file(struct inode *inode, struct file *file,
> struct btrfs_ioctl_defrag_range_args *range,
> u64 newer_than, unsigned long max_pages);
> diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
> index 48890826b5e6..f639dde2a679 100644
> --- a/fs/btrfs/dev-replace.c
> +++ b/fs/btrfs/dev-replace.c
> @@ -986,7 +986,7 @@ static int btrfs_dev_replace_kthread(void *data)
> return 0;
> }
>
> -int btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
> +int __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
> {
> if (!dev_replace->is_valid)
> return 0;
> diff --git a/fs/btrfs/dev-replace.h b/fs/btrfs/dev-replace.h
> index 78c5d8f1adda..60b70dacc299 100644
> --- a/fs/btrfs/dev-replace.h
> +++ b/fs/btrfs/dev-replace.h
> @@ -17,6 +17,6 @@ void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
> int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info);
> void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info);
> int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info);
> -int btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace);
> +int __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace);
>
> #endif
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index de730e56d3f5..55b41d5e7ea9 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -541,7 +541,7 @@ static noinline int btrfs_ioctl_fitrim(struct file *file, void __user *arg)
> return 0;
> }
>
> -int btrfs_is_empty_uuid(u8 *uuid)
> +int __pure btrfs_is_empty_uuid(u8 *uuid)
> {
> int i;
>
> diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
> index 98dc092a905e..f32993efbf61 100644
> --- a/fs/btrfs/space-info.c
> +++ b/fs/btrfs/space-info.c
> @@ -10,7 +10,7 @@
> #include "transaction.h"
> #include "block-group.h"
>
> -u64 btrfs_space_info_used(struct btrfs_space_info *s_info,
> +u64 __pure btrfs_space_info_used(struct btrfs_space_info *s_info,
> bool may_use_included)
> {
> ASSERT(s_info);
> diff --git a/fs/btrfs/space-info.h b/fs/btrfs/space-info.h
> index 8867e84aa33d..2d8c811a9792 100644
> --- a/fs/btrfs/space-info.h
> +++ b/fs/btrfs/space-info.h
> @@ -116,7 +116,7 @@ void btrfs_update_space_info(struct btrfs_fs_info *info, u64 flags,
> struct btrfs_space_info **space_info);
> struct btrfs_space_info *btrfs_find_space_info(struct btrfs_fs_info *info,
> u64 flags);
> -u64 btrfs_space_info_used(struct btrfs_space_info *s_info,
> +u64 __pure btrfs_space_info_used(struct btrfs_space_info *s_info,
> bool may_use_included);
> void btrfs_clear_space_info_full(struct btrfs_fs_info *info);
> void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
>
