Use separate bitmaps for each nodes in the cluster

On-disk format:

0                    4k                     8k                    12k
-------------------------------------------------------------------
| idle                | md super            | bm super [0] + bits |
| bm bits[0, contd]   | bm super[1] + bits  | bm bits[1, contd]   |
| bm super[2] + bits  | bm bits [2, contd]  | bm super[3] + bits  |
| bm bits [3, contd]  |                     |                     |

Bitmap super has a field nodes, which defines the maximum number
of nodes the device can use. While reading the bitmap super, if
the cluster finds out that the number of nodes is > 0:
1. Requests the md-cluster module.
2. Calls md_cluster_ops->join(), which sets up clustering such as
   joining DLM lockspace.

Since the first time, the first bitmap is read. After the call
to the cluster_setup, the bitmap offset is adjusted and the
superblock is re-read. This also ensures the bitmap is read
the bitmap lock (when bitmap lock is introduced in later patches)

Questions:
1. cluster name is repeated in all bitmap supers. Is that okay?

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

3 files changed, 64 insertions, 10 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index b43a75a246e7..b1d94eee3346 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -205,6 +205,10 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
         struct block_device *bdev;
         struct mddev *mddev = bitmap->mddev;
         struct bitmap_storage *store = &bitmap->storage;
+        int node_offset = 0;
+
+        if (mddev_is_clustered(bitmap->mddev))
+                node_offset = bitmap->cluster_slot * store->file_pages;
 
         while ((rdev = next_active_rdev(rdev, mddev)) != NULL) {
                 int size = PAGE_SIZE;
@@ -549,6 +553,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
         unsigned long sectors_reserved = 0;
         int err = -EINVAL;
         struct page *sb_page;
+        int cluster_setup_done = 0;
 
         if (!bitmap->storage.file && !bitmap->mddev->bitmap_info.offset) {
                 chunksize = 128 * 1024 * 1024;
@@ -564,6 +569,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
                 return -ENOMEM;
         bitmap->storage.sb_page = sb_page;
 
+re_read:
         if (bitmap->storage.file) {
                 loff_t isize = i_size_read(bitmap->storage.file->f_mapping->host);
                 int bytes = isize > PAGE_SIZE ? PAGE_SIZE : isize;
@@ -579,6 +585,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
         if (err)
                 return err;
 
+        err = -EINVAL;
         sb = kmap_atomic(sb_page);
 
         chunksize = le32_to_cpu(sb->chunksize);
@@ -586,6 +593,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
         write_behind = le32_to_cpu(sb->write_behind);
         sectors_reserved = le32_to_cpu(sb->sectors_reserved);
         nodes = le32_to_cpu(sb->nodes);
+        strlcpy(bitmap->mddev->bitmap_info.cluster_name, sb->cluster_name, 64);
 
         /* verify that the bitmap-specific fields are valid */
         if (sb->magic != cpu_to_le32(BITMAP_MAGIC))
@@ -622,7 +630,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
                         goto out;
                 }
                 events = le64_to_cpu(sb->events);
-                if (events < bitmap->mddev->events) {
+                if (!nodes && (events < bitmap->mddev->events)) {
                         printk(KERN_INFO
                                "%s: bitmap file is out of date (%llu < %llu) "
                                "-- forcing full recovery\n",
@@ -639,8 +647,34 @@ static int bitmap_read_sb(struct bitmap *bitmap)
         bitmap->events_cleared = le64_to_cpu(sb->events_cleared);
         strlcpy(bitmap->mddev->bitmap_info.cluster_name, sb->cluster_name, 64);
         err = 0;
+
 out:
         kunmap_atomic(sb);
+        if (nodes && !cluster_setup_done) {
+                sector_t bm_blocks;
+
+                bm_blocks = sector_div(bitmap->mddev->resync_max_sectors, (chunksize >> 9));
+                bm_blocks = bm_blocks << 3;
+                /* We have bitmap supers at 4k boundaries, hence this
+                 * is hardcoded */
+                bm_blocks = DIV_ROUND_UP(bm_blocks, 4096);
+                err = md_setup_cluster(bitmap->mddev, nodes);
+                if (err) {
+                        pr_err("%s: Could not setup cluster service (%d)\n",
+                                        bmname(bitmap), err);
+                        goto out_no_sb;
+                }
+                bitmap->cluster_slot = md_cluster_ops->slot_number(bitmap->mddev);
+                bitmap->mddev->bitmap_info.offset +=
+                        bitmap->cluster_slot * (bm_blocks << 3);
+                pr_info("%s:%d bm slot: %d offset: %llu\n", __func__, __LINE__,
+                        bitmap->cluster_slot,
+                        (unsigned long long)bitmap->mddev->bitmap_info.offset);
+                cluster_setup_done = 1;
+                goto re_read;
+        }
+
+
 out_no_sb:
         if (test_bit(BITMAP_STALE, &bitmap->flags))
                 bitmap->events_cleared = bitmap->mddev->events;
@@ -651,8 +685,11 @@ out_no_sb:
         if (bitmap->mddev->bitmap_info.space == 0 ||
             bitmap->mddev->bitmap_info.space > sectors_reserved)
                 bitmap->mddev->bitmap_info.space = sectors_reserved;
-        if (err)
+        if (err) {
                 bitmap_print_sb(bitmap);
+                if (cluster_setup_done)
+                        md_cluster_stop(bitmap->mddev);
+        }
         return err;
 }
 
@@ -697,9 +734,10 @@ static inline struct page *filemap_get_page(struct bitmap_storage *store,
 }
 
 static int bitmap_storage_alloc(struct bitmap_storage *store,
-                                unsigned long chunks, int with_super)
+                                unsigned long chunks, int with_super,
+                                int slot_number)
 {
-        int pnum;
+        int pnum, offset = 0;
         unsigned long num_pages;
         unsigned long bytes;
 
@@ -708,6 +746,7 @@ static int bitmap_storage_alloc(struct bitmap_storage *store,
                 bytes += sizeof(bitmap_super_t);
 
         num_pages = DIV_ROUND_UP(bytes, PAGE_SIZE);
+        offset = slot_number * (num_pages - 1);
 
         store->filemap = kmalloc(sizeof(struct page *)
                                  * num_pages, GFP_KERNEL);
@@ -718,20 +757,22 @@ static int bitmap_storage_alloc(struct bitmap_storage *store,
                 store->sb_page = alloc_page(GFP_KERNEL|__GFP_ZERO);
                 if (store->sb_page == NULL)
                         return -ENOMEM;
-                store->sb_page->index = 0;
         }
+
         pnum = 0;
         if (store->sb_page) {
                 store->filemap[0] = store->sb_page;
                 pnum = 1;
+                store->sb_page->index = offset;
         }
+
         for ( ; pnum < num_pages; pnum++) {
                 store->filemap[pnum] = alloc_page(GFP_KERNEL|__GFP_ZERO);
                 if (!store->filemap[pnum]) {
                         store->file_pages = pnum;
                         return -ENOMEM;
                 }
-                store->filemap[pnum]->index = pnum;
+                store->filemap[pnum]->index = pnum + offset;
         }
         store->file_pages = pnum;
 
@@ -940,7 +981,7 @@ static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int n
  */
 static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
 {
-        unsigned long i, chunks, index, oldindex, bit;
+        unsigned long i, chunks, index, oldindex, bit, node_offset = 0;
         struct page *page = NULL;
         unsigned long bit_cnt = 0;
         struct file *file;
@@ -986,6 +1027,9 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
         if (!bitmap->mddev->bitmap_info.external)
                 offset = sizeof(bitmap_super_t);
 
+        if (mddev_is_clustered(bitmap->mddev))
+                node_offset = bitmap->cluster_slot * (DIV_ROUND_UP(store->bytes, PAGE_SIZE));
+
         for (i = 0; i < chunks; i++) {
                 int b;
                 index = file_page_index(&bitmap->storage, i);
@@ -1006,7 +1050,7 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
                                         bitmap->mddev,
                                         bitmap->mddev->bitmap_info.offset,
                                         page,
-                                        index, count);
+                                        index + node_offset, count);
 
                         if (ret)
                                 goto err;
@@ -1212,7 +1256,6 @@ void bitmap_daemon_work(struct mddev *mddev)
              j < bitmap->storage.file_pages
                      && !test_bit(BITMAP_STALE, &bitmap->flags);
              j++) {
-
                 if (test_page_attr(bitmap, j,
                                    BITMAP_PAGE_DIRTY))
                         /* bitmap_unplug will handle the rest */
@@ -1596,6 +1639,9 @@ static void bitmap_free(struct bitmap *bitmap)
         if (!bitmap) /* there was no bitmap */
                 return;
 
+        if (mddev_is_clustered(bitmap->mddev) && bitmap->mddev->cluster_info)
+                md_cluster_stop(bitmap->mddev);
+
         /* Shouldn't be needed - but just in case.... */
         wait_event(bitmap->write_wait,
                    atomic_read(&bitmap->pending_writes) == 0);
@@ -1854,7 +1900,8 @@ int bitmap_resize(struct bitmap *bitmap, sector_t blocks,
         memset(&store, 0, sizeof(store));
         if (bitmap->mddev->bitmap_info.offset || bitmap->mddev->bitmap_info.file)
                 ret = bitmap_storage_alloc(&store, chunks,
-                                           !bitmap->mddev->bitmap_info.external);
+                                           !bitmap->mddev->bitmap_info.external,
+                                           bitmap->cluster_slot);
         if (ret)
                 goto err;
 
diff --git a/drivers/md/bitmap.h b/drivers/md/bitmap.h
index ec9032f105b8..4e9acb08bbe0 100644
--- a/drivers/md/bitmap.h
+++ b/drivers/md/bitmap.h
@@ -227,6 +227,7 @@ struct bitmap {
         wait_queue_head_t behind_wait;
 
         struct kernfs_node *sysfs_can_clear;
+        int cluster_slot;               /* Slot offset for clustered env */
 };
 
 /* the bitmap API */
diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
index 1f3c8f39ecb2..66700e244a40 100644
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -196,6 +196,12 @@ static int join(struct mddev *mddev, int nodes)
         if (ret)
                 goto err;
         wait_for_completion(&cinfo->completion);
+        if (nodes <= cinfo->slot_number) {
+                pr_err("md-cluster: Slot allotted(%d) greater than available slots(%d)", cinfo->slot_number - 1,
+                        nodes);
+                ret = -ERANGE;
+                goto err;
+        }
         cinfo->sb_lock = lockres_init(mddev, "cmd-super",
                                         NULL, 0);
         if (!cinfo->sb_lock) {