md/raid10: prepare data structures for handling replacement.

Allow each slot in the RAID10 to have 2 devices, the want_replacement
and the replacement.

Also an r10bio to have 2 bios, and for resync/recovery allocate the
second bio if there are any replacement devices.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 37 insertions, 24 deletions

diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h
index 7facfdf841f4..7c615613c381 100644
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -2,7 +2,7 @@
 #define _RAID10_H
 
 struct mirror_info {
-        struct md_rdev  *rdev;
+        struct md_rdev  *rdev, *replacement;
         sector_t        head_position;
         int             recovery_disabled;      /* matches
                                                  * mddev->recovery_disabled
@@ -18,12 +18,13 @@ struct r10conf {
         spinlock_t              device_lock;
 
         /* geometry */
-        int                     near_copies;  /* number of copies laid out raid0 style */
+        int                     near_copies;  /* number of copies laid out
+                                               * raid0 style */
         int                     far_copies;   /* number of copies laid out
                                                * at large strides across drives
                                                */
-        int                     far_offset;   /* far_copies are offset by 1 stripe
-                                               * instead of many
+        int                     far_offset;   /* far_copies are offset by 1
+                                               * stripe instead of many
                                                */
         int                     copies;       /* near_copies * far_copies.
                                                * must be <= raid_disks
@@ -34,10 +35,11 @@ struct r10conf {
                                                * 1 stripe.
                                                */
 
-        sector_t                dev_sectors;  /* temp copy of mddev->dev_sectors */
+        sector_t                dev_sectors;  /* temp copy of
+                                               * mddev->dev_sectors */
 
-        int chunk_shift; /* shift from chunks to sectors */
-        sector_t chunk_mask;
+        int                     chunk_shift; /* shift from chunks to sectors */
+        sector_t                chunk_mask;
 
         struct list_head        retry_list;
         /* queue pending writes and submit them on unplug */
@@ -45,20 +47,22 @@ struct r10conf {
         int                     pending_count;
 
         spinlock_t              resync_lock;
-        int nr_pending;
-        int nr_waiting;
-        int nr_queued;
-        int barrier;
+        int                     nr_pending;
+        int                     nr_waiting;
+        int                     nr_queued;
+        int                     barrier;
         sector_t                next_resync;
         int                     fullsync;  /* set to 1 if a full sync is needed,
                                             * (fresh device added).
                                             * Cleared when a sync completes.
                                             */
-
+        int                     have_replacement; /* There is at least one
+                                                   * replacement device.
+                                                   */
         wait_queue_head_t       wait_barrier;
 
-        mempool_t *r10bio_pool;
-        mempool_t *r10buf_pool;
+        mempool_t               *r10bio_pool;
+        mempool_t               *r10buf_pool;
         struct page             *tmppage;
 
         /* When taking over an array from a different personality, we store
@@ -98,11 +102,18 @@ struct r10bio {
          * When resyncing we also use one for each copy.
          * When reconstructing, we use 2 bios, one for read, one for write.
          * We choose the number when they are allocated.
+         * We sometimes need an extra bio to write to the replacement.
          */
         struct {
-                struct bio              *bio;
-                sector_t addr;
-                int devnum;
+                struct bio      *bio;
+                union {
+                        struct bio      *repl_bio; /* used for resync and
+                                                    * writes */
+                        struct md_rdev  *rdev;     /* used for reads
+                                                    * (read_slot >= 0) */
+                };
+                sector_t        addr;
+                int             devnum;
         } devs[0];
 };
 
@@ -121,17 +132,19 @@ struct r10bio {
 #define BIO_SPECIAL(bio) ((unsigned long)bio <= 2)
 
 /* bits for r10bio.state */
-#define R10BIO_Uptodate 0
-#define R10BIO_IsSync   1
-#define R10BIO_IsRecover 2
-#define R10BIO_Degraded 3
+enum r10bio_state {
+        R10BIO_Uptodate,
+        R10BIO_IsSync,
+        R10BIO_IsRecover,
+        R10BIO_Degraded,
 /* Set ReadError on bios that experience a read error
  * so that raid10d knows what to do with them.
  */
-#define R10BIO_ReadError 4
+        R10BIO_ReadError,
 /* If a write for this request means we can clear some
  * known-bad-block records, we set this flag.
  */
-#define R10BIO_MadeGood 5
-#define R10BIO_WriteError 6
+        R10BIO_MadeGood,
+        R10BIO_WriteError,
+};
 #endif