On Wed, Aug 28, 2019 at 09:19:52PM +0200, David Sterba wrote:
> On Mon, Aug 26, 2019 at 01:48:32PM +0200, Johannes Thumshirn wrote:
> > Create a structure to encode the type and length for the known on-disk
> > checksums.
> >
> > This makes it easier to add new checksums later.
> >
> > Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
> >
> > ---
> > Changes to v2:
> > - Really remove initializer macro *doh*
> >
> > Changes to v1:
> > - Remove initializer macro (David)
> > ---
> > fs/btrfs/ctree.h | 13 ++++++++-----
> > 1 file changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> > index b161224b5a0b..139354d02dfa 100644
> > --- a/fs/btrfs/ctree.h
> > +++ b/fs/btrfs/ctree.h
> > @@ -82,9 +82,12 @@ struct btrfs_ref;
> > */
> > #define BTRFS_LINK_MAX 65535U
> >
> > -/* four bytes for CRC32 */
> > -static const int btrfs_csum_sizes[] = { 4 };
> > -static const char *btrfs_csum_names[] = { "crc32c" };
> > +static const struct btrfs_csums {
> > + u16 size;
> > + const char *name;
> > +} btrfs_csums[] = {
> > + [BTRFS_CSUM_TYPE_CRC32] = { .size = 4, .name = "crc32c" },
> > +};
>
> In one of the previous iterations, I pointed out that the definition is
> in a header, thus each file that includes "ctree.h" (many of them)
> has a private copy of the table. With just crc32c it's just a few bytes
> that gets lost in the noise but now the table is going to be larger the
> impact will be noticeable.
With definitions moved to ctree.c and only exported the two helpers that
need btrfs_csumss
text data bss dec hex filename
1080108 17316 14912 1112336 10f910 btrfs.ko.before
1079655 17316 14912 1111883 10f74b btrfs.ko.after
The difference is 453.
