[XFS] refactor xfs_btree_readahead

[XFS] refactor xfs_btree_readahead

From: Dave Chinner <[email protected]>

Refactor xfs_btree_readahead to make it more readable:

(a) remove the inline xfs_btree_readahead wrapper and move all checks out

of line into the main routine.

(b) factor out helpers for short/long form btrees

(c) move check for root in inodes from the callers into
xfs_btree_readahead

[hch: split out from a big patch and minor cleanups]

SGI-PV: 985583

SGI-Modid: xfs-linux-melb:xfs-kern:32182a

Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: Lachlan McIlroy <[email protected]>
Signed-off-by: Bill O'Donnell <[email protected]>
Signed-off-by: David Chinner <[email protected]>