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btrfs: add const function attribute 

For some reason the attribute is called __attribute_const__ and not
__const, marks functions that have no observable effects on program
state, IOW not reading pointers, just the arguments and calculating a
value. Allows the compiler to do some optimizations, based on
-Wsuggest-attribute=const . The effects are rather small, though, about
60 bytes decrese of btrfs.ko.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2019-10-01 19:57:37 +02:00
parent b105e92755
commit 4143cb8b6f
4 changed files with 4 additions and 4 deletions
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2
fs/btrfs/ctree.h
View File

@ -3141,7 +3141,7 @@ __cold
void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function,
unsigned int line, int errno, const char *fmt, ...);
const char *btrfs_decode_error(int errno);
const char * __attribute_const__ btrfs_decode_error(int errno);
__cold
void __btrfs_abort_transaction(struct btrfs_trans_handle *trans,

2
fs/btrfs/super.c
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@ -66,7 +66,7 @@ static struct file_system_type btrfs_root_fs_type;
static int btrfs_remount(struct super_block *sb, int *flags, char *data);
const char *btrfs_decode_error(int errno)
const char * __attribute_const__ btrfs_decode_error(int errno)
{
char *errstr = "unknown";

2
fs/btrfs/volumes.c
View File

@ -297,7 +297,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
DEFINE_MUTEX(uuid_mutex);
static LIST_HEAD(fs_uuids);
struct list_head *btrfs_get_fs_uuids(void)
struct list_head * __attribute_const__ btrfs_get_fs_uuids(void)
{
return &fs_uuids;
}

2
fs/btrfs/volumes.h
View File

@ -571,7 +571,7 @@ static inline enum btrfs_raid_types btrfs_bg_flags_to_raid_index(u64 flags)
void btrfs_commit_device_sizes(struct btrfs_transaction *trans);
struct list_head *btrfs_get_fs_uuids(void);
struct list_head * __attribute_const__ btrfs_get_fs_uuids(void);
void btrfs_set_fs_info_ptr(struct btrfs_fs_info *fs_info);
void btrfs_reset_fs_info_ptr(struct btrfs_fs_info *fs_info);
bool btrfs_check_rw_degradable(struct btrfs_fs_info *fs_info,