Re: [PATCH 0/3] xfs: reduce boilerplate around xfs_btree_init_block

Eric Sandeen
2017-01-16T23:13:35Z

On 12/22/16 11:41 AM, Eric Sandeen wrote:
> We have this pattern all over the kernel & userspace:
>
> if (xfs_sb_version_hascrc(&mp->m_sb))
> xfs_btree_init_block(mp, bp, XFS_ABTB_CRC_MAGIC, 0, 1,
> agno, XFS_BTREE_CRC_BLOCKS);
> else
> xfs_btree_init_block(mp, bp, XFS_ABTB_MAGIC, 0, 1,
> agno, 0);
>
> The last flag (XFS_BTREE_CRC_BLOCKS) can be gleaned from
> the features on the superblock via mp just as the if/else does,
> so no need to pass that in from the caller. That's patch 1.

Ping on this series?

Thanks,
-Eric

> Then the difference is simply CRC vs not-CRC magic. This can also
> be determined inside the called function by passing in a btree number,
> and looking up the proper magic in the xfs_magics array.
>
> patch2 makes xfs_btree_magic() more generic, taking a
> crc flag & btnum, instead of just a cursor.
>
> patch3 then makes use of xfs_btree_magic in the block init routine
> to determine the proper magic.
>
> With those changes, the if/else can go away, and we can simply call:
>
> xfs_btree_init_block(mp, bp, XFS_BTNUM_BNO, 0, 1, agno, 0);
>
> and let the lower function sort out crc vs. no crc differences
> by itself.
>
> It's not a huge reduction in code, but it reduces a lot of the
> boilerplate, particularly in growfs code. This may also make it
> slightly easier to factor the growfs tree init code into a loop
> (not sure about that, yet) and/or to move mkfs & growfs tree init
> code into a libxfs/ call.
>
> libxfs/xfs_bmap.c | 19 ++++---------------
> libxfs/xfs_bmap_btree.c | 10 ++--------
> libxfs/xfs_btree.c | 34 +++++++++++++++++++++-------------
> libxfs/xfs_btree.h | 4 ++--
> libxfs/xfs_types.h | 2 ++
> xfs_fsops.c | 39 +++++++++------------------------------
> 6 files changed, 40 insertions(+), 68 deletions(-)
>
> -Eric
> --
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