[PATCH] md: Core of raid5 resize process

This patch provides the core of the resize/expand process.

sync_request notices if a 'reshape' is happening and acts accordingly.

It allocated new stripe_heads for the next chunk-wide-stripe in the target
geometry, marking them STRIPE_EXPANDING.

Then it finds which stripe heads in the old geometry can provide data needed
by these and marks them STRIPE_EXPAND_SOURCE.  This causes stripe_handle to
read all blocks on those stripes.

Once all blocks on a STRIPE_EXPAND_SOURCE stripe_head are read, any that are
needed are copied into the corresponding STRIPE_EXPANDING stripe_head.  Once a
STRIPE_EXPANDING stripe_head is full, it is marks STRIPE_EXPAND_READY and then
is written out and released.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 181 insertions, 26 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index c7b7656f9aa5..8e65986bc63f 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2165,7 +2165,9 @@ action_show(mddev_t *mddev, char *page)
         char *type = "idle";
         if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
             test_bit(MD_RECOVERY_NEEDED, &mddev->recovery)) {
-                if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
+                if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
+                        type = "reshape";
+                else if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
                         if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
                                 type = "resync";
                         else if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
@@ -4088,8 +4090,10 @@ static void status_resync(struct seq_file *seq, mddev_t * mddev)
                 seq_printf(seq, "] ");
         }
         seq_printf(seq, " %s =%3u.%u%% (%llu/%llu)",
+                   (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery)?
+                    "reshape" :
                       (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ?
-                       "resync" : "recovery"),
+                       "resync" : "recovery")),
                       per_milli/10, per_milli % 10,
                    (unsigned long long) resync,
                    (unsigned long long) max_blocks);
@@ -4543,7 +4547,9 @@ static void md_do_sync(mddev_t *mddev)
                  */
                 max_sectors = mddev->resync_max_sectors;
                 mddev->resync_mismatches = 0;
-        } else
+        } else if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
+                max_sectors = mddev->size << 1;
+        else
                 /* recovery follows the physical size of devices */
                 max_sectors = mddev->size << 1;
 
@@ -4679,6 +4685,8 @@ static void md_do_sync(mddev_t *mddev)
         mddev->pers->sync_request(mddev, max_sectors, &skipped, 1);
 
         if (!test_bit(MD_RECOVERY_ERR, &mddev->recovery) &&
+            test_bit(MD_RECOVERY_SYNC, &mddev->recovery) &&
+            !test_bit(MD_RECOVERY_CHECK, &mddev->recovery) &&
             mddev->curr_resync > 2 &&
             mddev->curr_resync >= mddev->recovery_cp) {
                 if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 7a6df515b008..56cba8d3e398 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -93,11 +93,11 @@ static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
                                 if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
                                         md_wakeup_thread(conf->mddev->thread);
                         }
-                        list_add_tail(&sh->lru, &conf->inactive_list);
                         atomic_dec(&conf->active_stripes);
-                        if (!conf->inactive_blocked ||
-                            atomic_read(&conf->active_stripes) < (conf->max_nr_stripes*3/4))
+                        if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
+                                list_add_tail(&sh->lru, &conf->inactive_list);
                                 wake_up(&conf->wait_for_stripe);
+                        }
                 }
         }
 }
@@ -273,9 +273,8 @@ static struct stripe_head *get_active_stripe(raid5_conf_t *conf, sector_t sector
                         } else {
                                 if (!test_bit(STRIPE_HANDLE, &sh->state))
                                         atomic_inc(&conf->active_stripes);
-                                if (list_empty(&sh->lru))
-                                        BUG();
-                                list_del_init(&sh->lru);
+                                if (!list_empty(&sh->lru))
+                                        list_del_init(&sh->lru);
                         }
                 }
         } while (sh == NULL);
@@ -1035,6 +1034,18 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
         return 0;
 }
 
+static int stripe_to_pdidx(sector_t stripe, raid5_conf_t *conf, int disks)
+{
+        int sectors_per_chunk = conf->chunk_size >> 9;
+        sector_t x = stripe;
+        int pd_idx, dd_idx;
+        int chunk_offset = sector_div(x, sectors_per_chunk);
+        stripe = x;
+        raid5_compute_sector(stripe*(disks-1)*sectors_per_chunk
+                             + chunk_offset, disks, disks-1, &dd_idx, &pd_idx, conf);
+        return pd_idx;
+}
+
 
 /*
  * handle_stripe - do things to a stripe.
@@ -1061,7 +1072,7 @@ static void handle_stripe(struct stripe_head *sh)
         struct bio *return_bi= NULL;
         struct bio *bi;
         int i;
-        int syncing;
+        int syncing, expanding, expanded;
         int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
         int non_overwrite = 0;
         int failed_num=0;
@@ -1076,6 +1087,8 @@ static void handle_stripe(struct stripe_head *sh)
         clear_bit(STRIPE_DELAYED, &sh->state);
 
         syncing = test_bit(STRIPE_SYNCING, &sh->state);
+        expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
+        expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
         /* Now to look around and see what can be done */
 
         rcu_read_lock();
@@ -1268,13 +1281,14 @@ static void handle_stripe(struct stripe_head *sh)
          * parity, or to satisfy requests
          * or to load a block that is being partially written.
          */
-        if (to_read || non_overwrite || (syncing && (uptodate < disks))) {
+        if (to_read || non_overwrite || (syncing && (uptodate < disks)) || expanding) {
                 for (i=disks; i--;) {
                         dev = &sh->dev[i];
                         if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
                             (dev->toread ||
                              (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
                              syncing ||
+                             expanding ||
                              (failed && (sh->dev[failed_num].toread ||
                                          (sh->dev[failed_num].towrite && !test_bit(R5_OVERWRITE, &sh->dev[failed_num].flags))))
                                     )
@@ -1464,13 +1478,76 @@ static void handle_stripe(struct stripe_head *sh)
                         set_bit(R5_Wantwrite, &dev->flags);
                         set_bit(R5_ReWrite, &dev->flags);
                         set_bit(R5_LOCKED, &dev->flags);
+                        locked++;
                 } else {
                         /* let's read it back */
                         set_bit(R5_Wantread, &dev->flags);
                         set_bit(R5_LOCKED, &dev->flags);
+                        locked++;
                 }
         }
 
+        if (expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
+                /* Need to write out all blocks after computing parity */
+                sh->disks = conf->raid_disks;
+                sh->pd_idx = stripe_to_pdidx(sh->sector, conf, conf->raid_disks);
+                compute_parity(sh, RECONSTRUCT_WRITE);
+                for (i= conf->raid_disks; i--;) {
+                        set_bit(R5_LOCKED, &sh->dev[i].flags);
+                        locked++;
+                        set_bit(R5_Wantwrite, &sh->dev[i].flags);
+                }
+                clear_bit(STRIPE_EXPANDING, &sh->state);
+        } else if (expanded) {
+                clear_bit(STRIPE_EXPAND_READY, &sh->state);
+                wake_up(&conf->wait_for_overlap);
+                md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
+        }
+
+        if (expanding && locked == 0) {
+                /* We have read all the blocks in this stripe and now we need to
+                 * copy some of them into a target stripe for expand.
+                 */
+                clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
+                for (i=0; i< sh->disks; i++)
+                        if (i != sh->pd_idx) {
+                                int dd_idx, pd_idx, j;
+                                struct stripe_head *sh2;
+
+                                sector_t bn = compute_blocknr(sh, i);
+                                sector_t s = raid5_compute_sector(bn, conf->raid_disks,
+                                                                  conf->raid_disks-1,
+                                                                  &dd_idx, &pd_idx, conf);
+                                sh2 = get_active_stripe(conf, s, conf->raid_disks, pd_idx, 1);
+                                if (sh2 == NULL)
+                                        /* so far only the early blocks of this stripe
+                                         * have been requested.  When later blocks
+                                         * get requested, we will try again
+                                         */
+                                        continue;
+                                if(!test_bit(STRIPE_EXPANDING, &sh2->state) ||
+                                   test_bit(R5_Expanded, &sh2->dev[dd_idx].flags)) {
+                                        /* must have already done this block */
+                                        release_stripe(sh2);
+                                        continue;
+                                }
+                                memcpy(page_address(sh2->dev[dd_idx].page),
+                                       page_address(sh->dev[i].page),
+                                       STRIPE_SIZE);
+                                set_bit(R5_Expanded, &sh2->dev[dd_idx].flags);
+                                set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
+                                for (j=0; j<conf->raid_disks; j++)
+                                        if (j != sh2->pd_idx &&
+                                            !test_bit(R5_Expanded, &sh2->dev[j].flags))
+                                                break;
+                                if (j == conf->raid_disks) {
+                                        set_bit(STRIPE_EXPAND_READY, &sh2->state);
+                                        set_bit(STRIPE_HANDLE, &sh2->state);
+                                }
+                                release_stripe(sh2);
+                        }
+        }
+
         spin_unlock(&sh->lock);
 
         while ((bi=return_bi)) {
@@ -1509,7 +1586,7 @@ static void handle_stripe(struct stripe_head *sh)
                 rcu_read_unlock();
  
                 if (rdev) {
-                        if (syncing)
+                        if (syncing || expanding || expanded)
                                 md_sync_acct(rdev->bdev, STRIPE_SECTORS);
 
                         bi->bi_bdev = rdev->bdev;
@@ -1757,12 +1834,8 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
 {
         raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
         struct stripe_head *sh;
-        int sectors_per_chunk = conf->chunk_size >> 9;
-        sector_t x;
-        unsigned long stripe;
-        int chunk_offset;
-        int dd_idx, pd_idx;
-        sector_t first_sector;
+        int pd_idx;
+        sector_t first_sector, last_sector;
         int raid_disks = conf->raid_disks;
         int data_disks = raid_disks-1;
         sector_t max_sector = mddev->size << 1;
@@ -1781,6 +1854,80 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
 
                 return 0;
         }
+
+        if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery)) {
+                /* reshaping is quite different to recovery/resync so it is
+                 * handled quite separately ... here.
+                 *
+                 * On each call to sync_request, we gather one chunk worth of
+                 * destination stripes and flag them as expanding.
+                 * Then we find all the source stripes and request reads.
+                 * As the reads complete, handle_stripe will copy the data
+                 * into the destination stripe and release that stripe.
+                 */
+                int i;
+                int dd_idx;
+                for (i=0; i < conf->chunk_size/512; i+= STRIPE_SECTORS) {
+                        int j;
+                        int skipped = 0;
+                        pd_idx = stripe_to_pdidx(sector_nr+i, conf, conf->raid_disks);
+                        sh = get_active_stripe(conf, sector_nr+i,
+                                               conf->raid_disks, pd_idx, 0);
+                        set_bit(STRIPE_EXPANDING, &sh->state);
+                        /* If any of this stripe is beyond the end of the old
+                         * array, then we need to zero those blocks
+                         */
+                        for (j=sh->disks; j--;) {
+                                sector_t s;
+                                if (j == sh->pd_idx)
+                                        continue;
+                                s = compute_blocknr(sh, j);
+                                if (s < (mddev->array_size<<1)) {
+                                        skipped = 1;
+                                        continue;
+                                }
+                                memset(page_address(sh->dev[j].page), 0, STRIPE_SIZE);
+                                set_bit(R5_Expanded, &sh->dev[j].flags);
+                                set_bit(R5_UPTODATE, &sh->dev[j].flags);
+                        }
+                        if (!skipped) {
+                                set_bit(STRIPE_EXPAND_READY, &sh->state);
+                                set_bit(STRIPE_HANDLE, &sh->state);
+                        }
+                        release_stripe(sh);
+                }
+                spin_lock_irq(&conf->device_lock);
+                conf->expand_progress = (sector_nr + i)*(conf->raid_disks-1);
+                spin_unlock_irq(&conf->device_lock);
+                /* Ok, those stripe are ready. We can start scheduling
+                 * reads on the source stripes.
+                 * The source stripes are determined by mapping the first and last
+                 * block on the destination stripes.
+                 */
+                raid_disks = conf->previous_raid_disks;
+                data_disks = raid_disks - 1;
+                first_sector =
+                        raid5_compute_sector(sector_nr*(conf->raid_disks-1),
+                                             raid_disks, data_disks,
+                                             &dd_idx, &pd_idx, conf);
+                last_sector =
+                        raid5_compute_sector((sector_nr+conf->chunk_size/512)
+                                               *(conf->raid_disks-1) -1,
+                                             raid_disks, data_disks,
+                                             &dd_idx, &pd_idx, conf);
+                if (last_sector >= (mddev->size<<1))
+                        last_sector = (mddev->size<<1)-1;
+                while (first_sector <= last_sector) {
+                        pd_idx = stripe_to_pdidx(first_sector, conf, conf->previous_raid_disks);
+                        sh = get_active_stripe(conf, first_sector,
+                                               conf->previous_raid_disks, pd_idx, 0);
+                        set_bit(STRIPE_EXPAND_SOURCE, &sh->state);
+                        set_bit(STRIPE_HANDLE, &sh->state);
+                        release_stripe(sh);
+                        first_sector += STRIPE_SECTORS;
+                }
+                return conf->chunk_size>>9;
+        }
         /* if there is 1 or more failed drives and we are trying
          * to resync, then assert that we are finished, because there is
          * nothing we can do.
@@ -1799,13 +1946,7 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
                 return sync_blocks * STRIPE_SECTORS; /* keep things rounded to whole stripes */
         }
 
-        x = sector_nr;
-        chunk_offset = sector_div(x, sectors_per_chunk);
-        stripe = x;
-        BUG_ON(x != stripe);
-
-        first_sector = raid5_compute_sector((sector_t)stripe*data_disks*sectors_per_chunk
-                + chunk_offset, raid_disks, data_disks, &dd_idx, &pd_idx, conf);
+        pd_idx = stripe_to_pdidx(sector_nr, conf, raid_disks);
         sh = get_active_stripe(conf, sector_nr, raid_disks, pd_idx, 1);
         if (sh == NULL) {
                 sh = get_active_stripe(conf, sector_nr, raid_disks, pd_idx, 0);
diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 617b9506c760..4e26ef2cacca 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -157,6 +157,9 @@ struct mddev_s
          * DONE:     thread is done and is waiting to be reaped
          * REQUEST:  user-space has requested a sync (used with SYNC)
          * CHECK:    user-space request for for check-only, no repair
+         * RESHAPE:  A reshape is happening
+         *
+         * If neither SYNC or RESHAPE are set, then it is a recovery.
          */
 #define MD_RECOVERY_RUNNING     0
 #define MD_RECOVERY_SYNC        1
@@ -166,6 +169,7 @@ struct mddev_s
 #define MD_RECOVERY_NEEDED      5
 #define MD_RECOVERY_REQUESTED   6
 #define MD_RECOVERY_CHECK       7
+#define MD_RECOVERY_RESHAPE     8
         unsigned long                   recovery;
 
         int                             in_sync;        /* know to not need resync */
diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index 6fa274aea2a0..55c738d50508 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -157,6 +157,7 @@ struct stripe_head {
 #define R5_ReadError    8       /* seen a read error here recently */
 #define R5_ReWrite      9       /* have tried to over-write the readerror */
 
+#define R5_Expanded     10      /* This block now has post-expand data */
 /*
  * Write method
  */
@@ -176,7 +177,8 @@ struct stripe_head {
 #define STRIPE_DEGRADED         7
 #define STRIPE_BIT_DELAY        8
 #define STRIPE_EXPANDING        9
-
+#define STRIPE_EXPAND_SOURCE    10
+#define STRIPE_EXPAND_READY     11
 /*
  * Plugging:
  *