The commit 607d432d referred a static int array defined in ctree.h, and a static inline function (btrfs_super_csum_size) using this array, the obvious problem is every c file using that function would have a local copy of that int array, multiple c files calling would result multiple copies of that array:
$ nm fs/btrfs/btrfs.ko | grep btrfs_csum_sizes 0000010c r btrfs_csum_sizes 00000114 r btrfs_csum_sizes 000001c0 r btrfs_csum_sizes 000005a0 r btrfs_csum_sizes the original commit has 4 c files called this static inline function, till now there are still those 4 c files calling it, so there are 4 copies of btrfs_csum_sizes; but future code may call it in more c files, resulting in more copies; fs/btrfs/ctree.h | 19 ++++++++++++++++- fs/btrfs/disk-io.c | 25 +++++++++++++++++---- fs/btrfs/file-item.c | 56 ++++++++++++++++++++++++++++--------------------- fs/btrfs/ioctl.c | 9 ++++--- fs/btrfs/tree-log.c | 10 +++++--- 5 files changed, 81 insertions(+), 38 deletions(-) multiple copies are just wasting memory; move it to a c file can avoid duplications; and since the inline function referred ARRAY_SIZE of that array, must know the array size at compile time, so cannot be inlined anyway. The cost is originally inlined function calling changed to external function calling. Signed-off-by: Cheng Renquan <crq...@gmail.com> --- fs/btrfs/ctree.c | 9 +++++++++ fs/btrfs/ctree.h | 9 +-------- 2 files changed, 10 insertions(+), 8 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index c3df14c..3a89207 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -24,6 +24,15 @@ #include "print-tree.h" #include "locking.h" +int btrfs_super_csum_size(struct btrfs_super_block *s) +{ + static const int btrfs_csum_sizes[] = { 4, 0 }; + + int t = btrfs_super_csum_type(s); + BUG_ON(t >= ARRAY_SIZE(btrfs_csum_sizes)); + return btrfs_csum_sizes[t]; +} + static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root *root, struct btrfs_path *path, int level); static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index e9bf864..99220ee 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -132,8 +132,6 @@ struct btrfs_ordered_sum; /* csum types */ #define BTRFS_CSUM_TYPE_CRC32 0 -static int btrfs_csum_sizes[] = { 4, 0 }; - /* four bytes for CRC32 */ #define BTRFS_EMPTY_DIR_SIZE 0 @@ -1877,12 +1875,7 @@ BTRFS_SETGET_STACK_FUNCS(super_incompat_flags, struct btrfs_super_block, BTRFS_SETGET_STACK_FUNCS(super_csum_type, struct btrfs_super_block, csum_type, 16); -static inline int btrfs_super_csum_size(struct btrfs_super_block *s) -{ - int t = btrfs_super_csum_type(s); - BUG_ON(t >= ARRAY_SIZE(btrfs_csum_sizes)); - return btrfs_csum_sizes[t]; -} +int btrfs_super_csum_size(struct btrfs_super_block *s); static inline unsigned long btrfs_leaf_data(struct extent_buffer *l) { -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html