raid5: refactor handle_stripe5 and handle_stripe6 (v3)

handle_stripe5 and handle_stripe6 have very deep logic paths handling the
various states of a stripe_head.  By introducing the 'stripe_head_state'
and 'r6_state' objects, large portions of the logic can be moved to
sub-routines.

'struct stripe_head_state' consumes all of the automatic variables that previously
stood alone in handle_stripe5,6.  'struct r6_state' contains the handle_stripe6
specific variables like p_failed and q_failed.

One of the nice side effects of the 'stripe_head_state' change is that it
allows for further reductions in code duplication between raid5 and raid6.
The following new routines are shared between raid5 and raid6:

	handle_completed_write_requests
	handle_requests_to_failed_array
	handle_stripe_expansion

Changes:
* v2: fixed 'conf->raid_disk-1' for the raid6 'handle_stripe_expansion' path
* v3: removed the unused 'dirty' field from struct stripe_head_state
* v3: coalesced open coded bi_end_io routines into return_io()

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-By: NeilBrown <neilb@suse.de>

1 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index d8286db60b96..b99d354f6128 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -145,6 +145,22 @@ struct stripe_head {
                 unsigned long   flags;
         } dev[1]; /* allocated with extra space depending of RAID geometry */
 };
+
+/* stripe_head_state - collects and tracks the dynamic state of a stripe_head
+ *     for handle_stripe.  It is only valid under spin_lock(sh->lock);
+ */
+struct stripe_head_state {
+        int syncing, expanding, expanded;
+        int locked, uptodate, to_read, to_write, failed, written;
+        int non_overwrite;
+        int failed_num;
+};
+
+/* r6_state - extra state data only relevant to r6 */
+struct r6_state {
+        int p_failed, q_failed, qd_idx, failed_num[2];
+};
+
 /* Flags */
 #define R5_UPTODATE     0       /* page contains current data */
 #define R5_LOCKED       1       /* IO has been submitted on "req" */