drbd: prepare for new striped layout of activity log

Introduce two new on-disk meta data fields: al_stripes and al_stripe_size_4k
The intended use case is activity log on RAID 0 or similar.
Logically consecutive transactions will advance their on-disk position
by al_stripe_size_4k 4kB (transaction sized) blocks.

Right now, these are still asserted to be the backward compatible
values al_stripes = 1, al_stripe_size_4k = 8 (which amounts to 32kB).

Also introduce a caching member for meta_dev_idx in the in-core
structure: even though it is initially passed in in the rcu-protected
disk_conf structure, it cannot change without a detach/attach cycle.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 69 insertions, 8 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 76faeab40c8f..7a2e07b45ecf 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2850,7 +2850,11 @@ struct meta_data_on_disk {
 	u32 bm_bytes_per_bit;  /* BM_BLOCK_SIZE */
 	u32 la_peer_max_bio_size;   /* last peer max_bio_size */
 
-	u8 reserved_u8[4096 - (7*8 + 8*4)];
+	/* see al_tr_number_to_on_disk_sector() */
+	u32 al_stripes;
+	u32 al_stripe_size_4k;
+
+	u8 reserved_u8[4096 - (7*8 + 10*4)];
 } __packed;
 
 /**
@@ -2898,7 +2902,10 @@ void drbd_md_sync(struct drbd_conf *mdev)
 	buffer->bm_offset = cpu_to_be32(mdev->ldev->md.bm_offset);
 	buffer->la_peer_max_bio_size = cpu_to_be32(mdev->peer_max_bio_size);
 
-	D_ASSERT(drbd_md_ss__(mdev, mdev->ldev) == mdev->ldev->md.md_offset);
+	buffer->al_stripes = cpu_to_be32(mdev->ldev->md.al_stripes);
+	buffer->al_stripe_size_4k = cpu_to_be32(mdev->ldev->md.al_stripe_size_4k);
+
+	D_ASSERT(drbd_md_ss(mdev->ldev) == mdev->ldev->md.md_offset);
 	sector = mdev->ldev->md.md_offset;
 
 	if (drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)) {
@@ -2916,13 +2923,60 @@ out:
 	put_ldev(mdev);
 }
 
+static int check_activity_log_stripe_size(struct drbd_conf *mdev,
+		struct meta_data_on_disk *on_disk,
+		struct drbd_md *in_core)
+{
+	u32 al_stripes = be32_to_cpu(on_disk->al_stripes);
+	u32 al_stripe_size_4k = be32_to_cpu(on_disk->al_stripe_size_4k);
+	u64 al_size_4k;
+
+	/* both not set: default to old fixed size activity log */
+	if (al_stripes == 0 && al_stripe_size_4k == 0) {
+		al_stripes = 1;
+		al_stripe_size_4k = MD_32kB_SECT/8;
+	}
+
+	/* some paranoia plausibility checks */
+
+	/* we need both values to be set */
+	if (al_stripes == 0 || al_stripe_size_4k == 0)
+		goto err;
+
+	al_size_4k = (u64)al_stripes * al_stripe_size_4k;
+
+	/* Upper limit of activity log area, to avoid potential overflow
+	 * problems in al_tr_number_to_on_disk_sector(). As right now, more
+	 * than 72 * 4k blocks total only increases the amount of history,
+	 * limiting this arbitrarily to 16 GB is not a real limitation ;-)  */
+	if (al_size_4k > (16 * 1024 * 1024/4))
+		goto err;
+
+	/* Lower limit: we need at least 8 transaction slots (32kB)
+	 * to not break existing setups */
+	if (al_size_4k < MD_32kB_SECT/8)
+		goto err;
+
+	in_core->al_stripe_size_4k = al_stripe_size_4k;
+	in_core->al_stripes = al_stripes;
+	in_core->al_size_4k = al_size_4k;
+
+	return 0;
+err:
+	dev_err(DEV, "invalid activity log striping: al_stripes=%u, al_stripe_size_4k=%u\n",
+			al_stripes, al_stripe_size_4k);
+	return -EINVAL;
+}
+
 /**
  * drbd_md_read() - Reads in the meta data super block
  * @mdev:	DRBD device.
  * @bdev:	Device from which the meta data should be read in.
  *
- * Return 0 (NO_ERROR) on success, and an enum drbd_ret_code in case
+ * Return NO_ERROR on success, and an enum drbd_ret_code in case
  * something goes wrong.
+ *
+ * Called exactly once during drbd_adm_attach()
  */
 int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
 {
@@ -2937,6 +2991,10 @@ int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
 	if (!buffer)
 		goto out;
 
+	/* First, figure out where our meta data superblock is located. */
+	bdev->md.meta_dev_idx = bdev->disk_conf->meta_dev_idx;
+	bdev->md.md_offset = drbd_md_ss(bdev);
+
 	if (drbd_md_sync_page_io(mdev, bdev, bdev->md.md_offset, READ)) {
 		/* NOTE: can't do normal error processing here as this is
 		   called BEFORE disk is attached */
@@ -2954,40 +3012,43 @@ int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
 		rv = ERR_MD_UNCLEAN;
 		goto err;
 	}
+
+	rv = ERR_MD_INVALID;
 	if (magic != DRBD_MD_MAGIC_08) {
 		if (magic == DRBD_MD_MAGIC_07)
 			dev_err(DEV, "Found old (0.7) meta data magic. Did you \"drbdadm create-md\"?\n");
 		else
 			dev_err(DEV, "Meta data magic not found. Did you \"drbdadm create-md\"?\n");
-		rv = ERR_MD_INVALID;
 		goto err;
 	}
+
+	if (check_activity_log_stripe_size(mdev, buffer, &bdev->md))
+		goto err;
+
 	if (be32_to_cpu(buffer->al_offset) != bdev->md.al_offset) {
 		dev_err(DEV, "unexpected al_offset: %d (expected %d)\n",
 		    be32_to_cpu(buffer->al_offset), bdev->md.al_offset);
-		rv = ERR_MD_INVALID;
 		goto err;
 	}
 	if (be32_to_cpu(buffer->bm_offset) != bdev->md.bm_offset) {
 		dev_err(DEV, "unexpected bm_offset: %d (expected %d)\n",
 		    be32_to_cpu(buffer->bm_offset), bdev->md.bm_offset);
-		rv = ERR_MD_INVALID;
 		goto err;
 	}
 	if (be32_to_cpu(buffer->md_size_sect) != bdev->md.md_size_sect) {
 		dev_err(DEV, "unexpected md_size: %u (expected %u)\n",
 		    be32_to_cpu(buffer->md_size_sect), bdev->md.md_size_sect);
-		rv = ERR_MD_INVALID;
 		goto err;
 	}
 
 	if (be32_to_cpu(buffer->bm_bytes_per_bit) != BM_BLOCK_SIZE) {
 		dev_err(DEV, "unexpected bm_bytes_per_bit: %u (expected %u)\n",
 		    be32_to_cpu(buffer->bm_bytes_per_bit), BM_BLOCK_SIZE);
-		rv = ERR_MD_INVALID;
 		goto err;
 	}
 
+	rv = NO_ERROR;
+
 	bdev->md.la_size_sect = be64_to_cpu(buffer->la_size);
 	for (i = UI_CURRENT; i < UI_SIZE; i++)
 		bdev->md.uuid[i] = be64_to_cpu(buffer->uuid[i]);