Re: [PATCH 06/10] btrfs: uninline btrfs_bg_flags_to_raid_index

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2021/7/26 下午8:15, David Sterba wrote:
> The helper does a simple translation from block group flags to index to
> the btrfs_raid_array table. There's no apparent reason to inline the
> function, the translation happens usually once per function and is not
> called in a loop.
>
> Making it a proper function saves quite some binary code (x86_64,
> release config):
>
>     text    data     bss     dec     hex filename
> 1164011   19253   14912 1198176  124860 pre/btrfs.ko
> 1161559   19253   14912 1195724  123ecc post/btrfs.ko
>
> DELTA: -2451

My memory says there used to be some option to allow the compiler to
uninline some functions, but I can't find it in the latest kernel.

It looks to me that this should really be something dependent on kernel
config/compiler optimization.

E.g. to allow -Os optimization to uninline such functions.

Thanks,
Qu

>
> Also add the const attribute as there are no side effects, this could
> help compiler to optimize a few things without the function body.
>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>   fs/btrfs/volumes.c | 26 ++++++++++++++++++++++++++
>   fs/btrfs/volumes.h | 27 +--------------------------
>   2 files changed, 27 insertions(+), 26 deletions(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 86846d6e58d0..19feb64586fc 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -153,6 +153,32 @@ const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = {
>   	},
>   };
>
> +/*
> + * Convert block group flags (BTRFS_BLOCK_GROUP_*) to btrfs_raid_types, which
> + * can be used as index to access btrfs_raid_array[].
> + */
> +enum btrfs_raid_types __attribute_const__ btrfs_bg_flags_to_raid_index(u64 flags)
> +{
> +	if (flags & BTRFS_BLOCK_GROUP_RAID10)
> +		return BTRFS_RAID_RAID10;
> +	else if (flags & BTRFS_BLOCK_GROUP_RAID1)
> +		return BTRFS_RAID_RAID1;
> +	else if (flags & BTRFS_BLOCK_GROUP_RAID1C3)
> +		return BTRFS_RAID_RAID1C3;
> +	else if (flags & BTRFS_BLOCK_GROUP_RAID1C4)
> +		return BTRFS_RAID_RAID1C4;
> +	else if (flags & BTRFS_BLOCK_GROUP_DUP)
> +		return BTRFS_RAID_DUP;
> +	else if (flags & BTRFS_BLOCK_GROUP_RAID0)
> +		return BTRFS_RAID_RAID0;
> +	else if (flags & BTRFS_BLOCK_GROUP_RAID5)
> +		return BTRFS_RAID_RAID5;
> +	else if (flags & BTRFS_BLOCK_GROUP_RAID6)
> +		return BTRFS_RAID_RAID6;
> +
> +	return BTRFS_RAID_SINGLE; /* BTRFS_BLOCK_GROUP_SINGLE */
> +}
> +
>   const char *btrfs_bg_type_to_raid_name(u64 flags)
>   {
>   	const int index = btrfs_bg_flags_to_raid_index(flags);
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 70c749eee3ad..b082250b42e0 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -566,32 +566,6 @@ static inline void btrfs_dev_stat_set(struct btrfs_device *dev,
>   	atomic_inc(&dev->dev_stats_ccnt);
>   }
>
> -/*
> - * Convert block group flags (BTRFS_BLOCK_GROUP_*) to btrfs_raid_types, which
> - * can be used as index to access btrfs_raid_array[].
> - */
> -static inline enum btrfs_raid_types btrfs_bg_flags_to_raid_index(u64 flags)
> -{
> -	if (flags & BTRFS_BLOCK_GROUP_RAID10)
> -		return BTRFS_RAID_RAID10;
> -	else if (flags & BTRFS_BLOCK_GROUP_RAID1)
> -		return BTRFS_RAID_RAID1;
> -	else if (flags & BTRFS_BLOCK_GROUP_RAID1C3)
> -		return BTRFS_RAID_RAID1C3;
> -	else if (flags & BTRFS_BLOCK_GROUP_RAID1C4)
> -		return BTRFS_RAID_RAID1C4;
> -	else if (flags & BTRFS_BLOCK_GROUP_DUP)
> -		return BTRFS_RAID_DUP;
> -	else if (flags & BTRFS_BLOCK_GROUP_RAID0)
> -		return BTRFS_RAID_RAID0;
> -	else if (flags & BTRFS_BLOCK_GROUP_RAID5)
> -		return BTRFS_RAID_RAID5;
> -	else if (flags & BTRFS_BLOCK_GROUP_RAID6)
> -		return BTRFS_RAID_RAID6;
> -
> -	return BTRFS_RAID_SINGLE; /* BTRFS_BLOCK_GROUP_SINGLE */
> -}
> -
>   void btrfs_commit_device_sizes(struct btrfs_transaction *trans);
>
>   struct list_head * __attribute_const__ btrfs_get_fs_uuids(void);
> @@ -601,6 +575,7 @@ void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info,
>   			       struct block_device *bdev,
>   			       const char *device_path);
>
> +enum btrfs_raid_types __attribute_const__ btrfs_bg_flags_to_raid_index(u64 flags);
>   int btrfs_bg_type_to_factor(u64 flags);
>   const char *btrfs_bg_type_to_raid_name(u64 flags);
>   int btrfs_verify_dev_extents(struct btrfs_fs_info *fs_info);
>