md: Fix handling of raid5 array which is being reshaped to fewer devices.

When a raid5 (or raid6) array is being reshaped to have fewer devices,
conf->raid_disks is the latter and hence smaller number of devices.
However sometimes we want to use a number which is the total number of
currently required devices - the larger of the 'old' and 'new' sizes.
Before we implemented reducing the number of devices, this was always
'new' i.e. ->raid_disks.
Now we need max(raid_disks, previous_raid_disks) in those places.

This particularly affects assembling an array that was shutdown while
in the middle of a reshape to fewer devices.

md.c needs a similar fix when interpreting the md metadata.

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

1 files changed, 18 insertions, 19 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index d4ce51b4d41b..c4366c9373c5 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1238,22 +1238,22 @@ static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
 static int grow_one_stripe(raid5_conf_t *conf)
 {
         struct stripe_head *sh;
+        int disks = max(conf->raid_disks, conf->previous_raid_disks);
         sh = kmem_cache_alloc(conf->slab_cache, GFP_KERNEL);
         if (!sh)
                 return 0;
-        memset(sh, 0, sizeof(*sh) + (conf->raid_disks-1)*sizeof(struct r5dev));
+        memset(sh, 0, sizeof(*sh) + (disks-1)*sizeof(struct r5dev));
         sh->raid_conf = conf;
         spin_lock_init(&sh->lock);
         #ifdef CONFIG_MULTICORE_RAID456
         init_waitqueue_head(&sh->ops.wait_for_ops);
         #endif
 
-        if (grow_buffers(sh, conf->raid_disks)) {
-                shrink_buffers(sh, conf->raid_disks);
+        if (grow_buffers(sh, disks)) {
+                shrink_buffers(sh, disks);
                 kmem_cache_free(conf->slab_cache, sh);
                 return 0;
         }
-        sh->disks = conf->raid_disks;
         /* we just created an active stripe so... */
         atomic_set(&sh->count, 1);
         atomic_inc(&conf->active_stripes);
@@ -1265,7 +1265,7 @@ static int grow_one_stripe(raid5_conf_t *conf)
 static int grow_stripes(raid5_conf_t *conf, int num)
 {
         struct kmem_cache *sc;
-        int devs = conf->raid_disks;
+        int devs = max(conf->raid_disks, conf->previous_raid_disks);
 
         sprintf(conf->cache_name[0],
                 "raid%d-%s", conf->level, mdname(conf->mddev));
@@ -3540,9 +3540,10 @@ static void unplug_slaves(mddev_t *mddev)
 {
         raid5_conf_t *conf = mddev->private;
         int i;
+        int devs = max(conf->raid_disks, conf->previous_raid_disks);
 
         rcu_read_lock();
-        for (i = 0; i < conf->raid_disks; i++) {
+        for (i = 0; i < devs; i++) {
                 mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
                 if (rdev && !test_bit(Faulty, &rdev->flags) && atomic_read(&rdev->nr_pending)) {
                         struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
@@ -4562,13 +4563,9 @@ raid5_size(mddev_t *mddev, sector_t sectors, int raid_disks)
 
         if (!sectors)
                 sectors = mddev->dev_sectors;
-        if (!raid_disks) {
+        if (!raid_disks)
                 /* size is defined by the smallest of previous and new size */
-                if (conf->raid_disks < conf->previous_raid_disks)
-                        raid_disks = conf->raid_disks;
-                else
-                        raid_disks = conf->previous_raid_disks;
-        }
+                raid_disks = min(conf->raid_disks, conf->previous_raid_disks);
 
         sectors &= ~((sector_t)mddev->chunk_sectors - 1);
         sectors &= ~((sector_t)mddev->new_chunk_sectors - 1);
@@ -4669,7 +4666,7 @@ static int raid5_alloc_percpu(raid5_conf_t *conf)
                         }
                         per_cpu_ptr(conf->percpu, cpu)->spare_page = spare_page;
                 }
-                scribble = kmalloc(scribble_len(conf->raid_disks), GFP_KERNEL);
+                scribble = kmalloc(conf->scribble_len, GFP_KERNEL);
                 if (!scribble) {
                         err = -ENOMEM;
                         break;
@@ -4690,7 +4687,7 @@ static int raid5_alloc_percpu(raid5_conf_t *conf)
 static raid5_conf_t *setup_conf(mddev_t *mddev)
 {
         raid5_conf_t *conf;
-        int raid_disk, memory;
+        int raid_disk, memory, max_disks;
         mdk_rdev_t *rdev;
         struct disk_info *disk;
 
@@ -4740,13 +4737,14 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
         conf->bypass_threshold = BYPASS_THRESHOLD;
 
         conf->raid_disks = mddev->raid_disks;
-        conf->scribble_len = scribble_len(conf->raid_disks);
         if (mddev->reshape_position == MaxSector)
                 conf->previous_raid_disks = mddev->raid_disks;
         else
                 conf->previous_raid_disks = mddev->raid_disks - mddev->delta_disks;
+        max_disks = max(conf->raid_disks, conf->previous_raid_disks);
+        conf->scribble_len = scribble_len(max_disks);
 
-        conf->disks = kzalloc(conf->raid_disks * sizeof(struct disk_info),
+        conf->disks = kzalloc(max_disks * sizeof(struct disk_info),
                               GFP_KERNEL);
         if (!conf->disks)
                 goto abort;
@@ -4764,7 +4762,7 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
 
         list_for_each_entry(rdev, &mddev->disks, same_set) {
                 raid_disk = rdev->raid_disk;
-                if (raid_disk >= conf->raid_disks
+                if (raid_disk >= max_disks
                     || raid_disk < 0)
                         continue;
                 disk = conf->disks + raid_disk;
@@ -4796,7 +4794,7 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
         }
 
         memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +
-                 conf->raid_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
+                 max_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
         if (grow_stripes(conf, conf->max_nr_stripes)) {
                 printk(KERN_ERR
                         "raid5: couldn't allocate %dkB for buffers\n", memory);
@@ -4921,7 +4919,8 @@ static int run(mddev_t *mddev)
                     test_bit(In_sync, &rdev->flags))
                         working_disks++;
 
-        mddev->degraded = conf->raid_disks - working_disks;
+        mddev->degraded = (max(conf->raid_disks, conf->previous_raid_disks)
+                           - working_disks);
 
         if (mddev->degraded > conf->max_degraded) {
                 printk(KERN_ERR "raid5: not enough operational devices for %s"