btrfs: factor out init_alloc_chunk_ctl

Factor out init_alloc_chunk_ctl() from __btrfs_alloc_chunk(). This
function initialises parameters of "struct alloc_chunk_ctl" for
allocation.  init_alloc_chunk_ctl() handles a common part of the
initialisation to load the RAID parameters from btrfs_raid_array.
init_alloc_chunk_ctl_policy_regular() decides some parameters for its
allocation.

The last "else" case in the original code is moved to
__btrfs_alloc_chunk() to handle the error case in the common code.
Replace the BUG_ON with ASSERT() and error return at the same time.
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Signed-off-by: NNaohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -4810,6 +4810,61 @@ struct alloc_chunk_ctl {
 	int ndevs;
 };
 
+static void init_alloc_chunk_ctl_policy_regular(
+				struct btrfs_fs_devices *fs_devices,
+				struct alloc_chunk_ctl *ctl)
+{
+	u64 type = ctl->type;
+
+	if (type & BTRFS_BLOCK_GROUP_DATA) {
+		ctl->max_stripe_size = SZ_1G;
+		ctl->max_chunk_size = BTRFS_MAX_DATA_CHUNK_SIZE;
+	} else if (type & BTRFS_BLOCK_GROUP_METADATA) {
+		/* For larger filesystems, use larger metadata chunks */
+		if (fs_devices->total_rw_bytes > 50ULL * SZ_1G)
+			ctl->max_stripe_size = SZ_1G;
+		else
+			ctl->max_stripe_size = SZ_256M;
+		ctl->max_chunk_size = ctl->max_stripe_size;
+	} else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
+		ctl->max_stripe_size = SZ_32M;
+		ctl->max_chunk_size = 2 * ctl->max_stripe_size;
+		ctl->devs_max = min_t(int, ctl->devs_max,
+				      BTRFS_MAX_DEVS_SYS_CHUNK);
+	} else {
+		BUG();
+	}
+
+	/* We don't want a chunk larger than 10% of writable space */
+	ctl->max_chunk_size = min(div_factor(fs_devices->total_rw_bytes, 1),
+				  ctl->max_chunk_size);
+}
+
+static void init_alloc_chunk_ctl(struct btrfs_fs_devices *fs_devices,
+				 struct alloc_chunk_ctl *ctl)
+{
+	int index = btrfs_bg_flags_to_raid_index(ctl->type);
+
+	ctl->sub_stripes = btrfs_raid_array[index].sub_stripes;
+	ctl->dev_stripes = btrfs_raid_array[index].dev_stripes;
+	ctl->devs_max = btrfs_raid_array[index].devs_max;
+	if (!ctl->devs_max)
+		ctl->devs_max = BTRFS_MAX_DEVS(fs_devices->fs_info);
+	ctl->devs_min = btrfs_raid_array[index].devs_min;
+	ctl->devs_increment = btrfs_raid_array[index].devs_increment;
+	ctl->ncopies = btrfs_raid_array[index].ncopies;
+	ctl->nparity = btrfs_raid_array[index].nparity;
+	ctl->ndevs = 0;
+
+	switch (fs_devices->chunk_alloc_policy) {
+	case BTRFS_CHUNK_ALLOC_REGULAR:
+		init_alloc_chunk_ctl_policy_regular(fs_devices, ctl);
+		break;
+	default:
+		BUG();
+	}
+}
+
 static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 			       u64 start, u64 type)
 {
@@ -4828,7 +4883,6 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	int ndevs;
 	int i;
 	int j;
-	int index;
 
 	if (!alloc_profile_is_valid(type, 0)) {
 		ASSERT(0);
@@ -4841,45 +4895,15 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 		return -ENOSPC;
 	}
 
-	ctl.start = start;
-	ctl.type = type;
-
-	index = btrfs_bg_flags_to_raid_index(type);
-
-	ctl.sub_stripes = btrfs_raid_array[index].sub_stripes;
-	ctl.dev_stripes = btrfs_raid_array[index].dev_stripes;
-	ctl.devs_max = btrfs_raid_array[index].devs_max;
-	if (!ctl.devs_max)
-		ctl.devs_max = BTRFS_MAX_DEVS(info);
-	ctl.devs_min = btrfs_raid_array[index].devs_min;
-	ctl.devs_increment = btrfs_raid_array[index].devs_increment;
-	ctl.ncopies = btrfs_raid_array[index].ncopies;
-	ctl.nparity = btrfs_raid_array[index].nparity;
-
-	if (type & BTRFS_BLOCK_GROUP_DATA) {
-		ctl.max_stripe_size = SZ_1G;
-		ctl.max_chunk_size = BTRFS_MAX_DATA_CHUNK_SIZE;
-	} else if (type & BTRFS_BLOCK_GROUP_METADATA) {
-		/* for larger filesystems, use larger metadata chunks */
-		if (fs_devices->total_rw_bytes > 50ULL * SZ_1G)
-			ctl.max_stripe_size = SZ_1G;
-		else
-			ctl.max_stripe_size = SZ_256M;
-		ctl.max_chunk_size = ctl.max_stripe_size;
-	} else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
-		ctl.max_stripe_size = SZ_32M;
-		ctl.max_chunk_size = 2 * ctl.max_stripe_size;
-		ctl.devs_max = min_t(int, ctl.devs_max,
-				      BTRFS_MAX_DEVS_SYS_CHUNK);
-	} else {
-		btrfs_err(info, "invalid chunk type 0x%llx requested",
-		       type);
-		BUG();
+	if (!(type & BTRFS_BLOCK_GROUP_TYPE_MASK)) {
+		btrfs_err(info, "invalid chunk type 0x%llx requested", type);
+		ASSERT(0);
+		return -EINVAL;
 	}
 
-	/* We don't want a chunk larger than 10% of writable space */
-	ctl.max_chunk_size = min(div_factor(fs_devices->total_rw_bytes, 1),
-				  ctl.max_chunk_size);
+	ctl.start = start;
+	ctl.type = type;
+	init_alloc_chunk_ctl(fs_devices, &ctl);
 
 	devices_info = kcalloc(fs_devices->rw_devices, sizeof(*devices_info),
 			       GFP_NOFS);