On Fri, May 30, 2025 at 10:52:43PM +0800, George Hu wrote:
> Eliminate redundant encode & decode function by using union for
> bch_compression_opt, which reduces code complexity.

order of bitfield members is not fixed, to do this you need #ifdef
__LITTLE_ENDIN_BITFIELD...

> 
> Signed-off-by: George Hu <[email protected]>
> ---
>  fs/bcachefs/compress.c | 17 +++++++++--------
>  fs/bcachefs/compress.h | 32 +++++++-------------------------
>  fs/bcachefs/extents.c  |  2 +-
>  3 files changed, 17 insertions(+), 34 deletions(-)
> 
> diff --git a/fs/bcachefs/compress.c b/fs/bcachefs/compress.c
> index 1bca61d17092..10e88e14f5ed 100644
> --- a/fs/bcachefs/compress.c
> +++ b/fs/bcachefs/compress.c
> @@ -336,7 +336,7 @@ static int attempt_compress(struct bch_fs *c,
>                           void *workspace,
>                           void *dst, size_t dst_len,
>                           void *src, size_t src_len,
> -                         struct bch_compression_opt compression)
> +                         union bch_compression_opt compression)
>  {
>       enum bch_compression_type compression_type =
>               __bch2_compression_opt_to_type[compression.type];
> @@ -426,7 +426,7 @@ static int attempt_compress(struct bch_fs *c,
>  static unsigned __bio_compress(struct bch_fs *c,
>                              struct bio *dst, size_t *dst_len,
>                              struct bio *src, size_t *src_len,
> -                            struct bch_compression_opt compression)
> +                            union bch_compression_opt compression)
>  {
>       struct bbuf src_data = { NULL }, dst_data = { NULL };
>       void *workspace;
> @@ -553,7 +553,7 @@ unsigned bch2_bio_compress(struct bch_fs *c,
>  
>       compression_type =
>               __bio_compress(c, dst, dst_len, src, src_len,
> -                            bch2_compression_decode(compression_opt));
> +                            (union bch_compression_opt){ .value = 
> compression_opt });
>  
>       dst->bi_iter.bi_size = orig_dst;
>       src->bi_iter.bi_size = orig_src;
> @@ -602,7 +602,8 @@ static int __bch2_check_set_has_compressed_data(struct 
> bch_fs *c, u64 f)
>  int bch2_check_set_has_compressed_data(struct bch_fs *c,
>                                      unsigned compression_opt)
>  {
> -     unsigned compression_type = 
> bch2_compression_decode(compression_opt).type;
> +     unsigned int compression_type = ((union bch_compression_opt){ .value = 
> compression_opt })
> +                                     .type;
>  
>       BUG_ON(compression_type >= ARRAY_SIZE(bch2_compression_opt_to_feature));
>  
> @@ -683,7 +684,7 @@ static int __bch2_fs_compress_init(struct bch_fs *c, u64 
> features)
>  
>  static u64 compression_opt_to_feature(unsigned v)
>  {
> -     unsigned type = bch2_compression_decode(v).type;
> +     unsigned int type = ((union bch_compression_opt){ .value = v }).type;
>  
>       return BIT_ULL(bch2_compression_opt_to_feature[type]);
>  }
> @@ -703,7 +704,7 @@ int bch2_opt_compression_parse(struct bch_fs *c, const 
> char *_val, u64 *res,
>  {
>       char *val = kstrdup(_val, GFP_KERNEL);
>       char *p = val, *type_str, *level_str;
> -     struct bch_compression_opt opt = { 0 };
> +     union bch_compression_opt opt = { 0 };
>       int ret;
>  
>       if (!val)
> @@ -736,7 +737,7 @@ int bch2_opt_compression_parse(struct bch_fs *c, const 
> char *_val, u64 *res,
>               opt.level = level;
>       }
>  
> -     *res = bch2_compression_encode(opt);
> +     *res = opt.value;
>  err:
>       kfree(val);
>       return ret;
> @@ -744,7 +745,7 @@ int bch2_opt_compression_parse(struct bch_fs *c, const 
> char *_val, u64 *res,
>  
>  void bch2_compression_opt_to_text(struct printbuf *out, u64 v)
>  {
> -     struct bch_compression_opt opt = bch2_compression_decode(v);
> +     union bch_compression_opt opt = { .value = v };
>  
>       if (opt.type < BCH_COMPRESSION_OPT_NR)
>               prt_str(out, bch2_compression_opts[opt.type]);
> diff --git a/fs/bcachefs/compress.h b/fs/bcachefs/compress.h
> index bec2f05bfd52..8cded510b2ac 100644
> --- a/fs/bcachefs/compress.h
> +++ b/fs/bcachefs/compress.h
> @@ -10,41 +10,23 @@ static const unsigned __bch2_compression_opt_to_type[] = {
>  #undef x
>  };
>  
> -struct bch_compression_opt {
> -     u8              type:4,
> -                     level:4;
> -};
> -
> -static inline struct bch_compression_opt __bch2_compression_decode(unsigned 
> v)
> -{
> -     return (struct bch_compression_opt) {
> -             .type   = v & 15,
> -             .level  = v >> 4,
> +union bch_compression_opt {
> +     u8 value;
> +     struct {
> +             u8 type:4, level:4;
>       };
> -}
> +};
>  
>  static inline bool bch2_compression_opt_valid(unsigned v)
>  {
> -     struct bch_compression_opt opt = __bch2_compression_decode(v);
> +     union bch_compression_opt opt = { .value = v };
>  
>       return opt.type < ARRAY_SIZE(__bch2_compression_opt_to_type) && 
> !(!opt.type && opt.level);
>  }
>  
> -static inline struct bch_compression_opt bch2_compression_decode(unsigned v)
> -{
> -     return bch2_compression_opt_valid(v)
> -             ? __bch2_compression_decode(v)
> -             : (struct bch_compression_opt) { 0 };
> -}
> -
> -static inline unsigned bch2_compression_encode(struct bch_compression_opt 
> opt)
> -{
> -     return opt.type|(opt.level << 4);
> -}
> -
>  static inline enum bch_compression_type 
> bch2_compression_opt_to_type(unsigned v)
>  {
> -     return __bch2_compression_opt_to_type[bch2_compression_decode(v).type];
> +     return __bch2_compression_opt_to_type[((union bch_compression_opt){ 
> .value = v }).type];
>  }
>  
>  struct bch_write_op;
> diff --git a/fs/bcachefs/extents.c b/fs/bcachefs/extents.c
> index 677cf453b332..64419c028662 100644
> --- a/fs/bcachefs/extents.c
> +++ b/fs/bcachefs/extents.c
> @@ -1512,7 +1512,7 @@ int bch2_bkey_ptrs_validate(struct bch_fs *c, struct 
> bkey_s_c k,
>                       const struct bch_extent_rebalance *r = 
> &entry->rebalance;
>  
>                       if (!bch2_compression_opt_valid(r->compression)) {
> -                             struct bch_compression_opt opt = 
> __bch2_compression_decode(r->compression);
> +                             union bch_compression_opt opt = { .value = 
> r->compression };
>                               prt_printf(err, "invalid compression opt %u:%u",
>                                          opt.type, opt.level);
>                               return -BCH_ERR_invalid_bkey;
> -- 
> 2.49.0
> 

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