btrfs: factor out gather_device_info()

Factor out gather_device_info() from __btrfs_alloc_chunk(). This
function iterates over devices list and gather information about
devices. This commit also introduces "max_avail" and
"dev_extent_min" to fold the same calculation to one variable.
This commit has no functional changes.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -4865,60 +4865,25 @@ static void init_alloc_chunk_ctl(struct btrfs_fs_devices *fs_devices,
 	}
 }
 
-static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
-			       u64 start, u64 type)
+static int gather_device_info(struct btrfs_fs_devices *fs_devices,
+			      struct alloc_chunk_ctl *ctl,
+			      struct btrfs_device_info *devices_info)
 {
-	struct btrfs_fs_info *info = trans->fs_info;
-	struct btrfs_fs_devices *fs_devices = info->fs_devices;
+	struct btrfs_fs_info *info = fs_devices->fs_info;
 	struct btrfs_device *device;
-	struct map_lookup *map = NULL;
-	struct extent_map_tree *em_tree;
-	struct extent_map *em;
-	struct btrfs_device_info *devices_info = NULL;
-	struct alloc_chunk_ctl ctl;
 	u64 total_avail;
-	int data_stripes;	/* number of stripes that count for
-				   block group size */
+	u64 dev_extent_want = ctl->max_stripe_size * ctl->dev_stripes;
+	u64 dev_extent_min = BTRFS_STRIPE_LEN * ctl->dev_stripes;
 	int ret;
-	int ndevs;
-	int i;
-	int j;
-
-	if (!alloc_profile_is_valid(type, 0)) {
-		ASSERT(0);
-		return -EINVAL;
-	}
-
-	if (list_empty(&fs_devices->alloc_list)) {
-		if (btrfs_test_opt(info, ENOSPC_DEBUG))
-			btrfs_debug(info, "%s: no writable device", __func__);
-		return -ENOSPC;
-	}
-
-	if (!(type & BTRFS_BLOCK_GROUP_TYPE_MASK)) {
-		btrfs_err(info, "invalid chunk type 0x%llx requested", type);
-		ASSERT(0);
-		return -EINVAL;
-	}
-
-	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);
-	if (!devices_info)
-		return -ENOMEM;
+	int ndevs = 0;
+	u64 max_avail;
+	u64 dev_offset;
 
 	/*
 	 * in the first pass through the devices list, we gather information
 	 * about the available holes on each device.
 	 */
-	ndevs = 0;
 	list_for_each_entry(device, &fs_devices->alloc_list, dev_alloc_list) {
-		u64 max_avail;
-		u64 dev_offset;
-
 		if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
 			WARN(1, KERN_ERR
 			       "BTRFS: read-only device in alloc_list\n");
@@ -4939,21 +4904,20 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 		if (total_avail == 0)
 			continue;
 
-		ret = find_free_dev_extent(
-			device, ctl.max_stripe_size * ctl.dev_stripes,
-			&dev_offset, &max_avail);
+		ret = find_free_dev_extent(device, dev_extent_want, &dev_offset,
+					   &max_avail);
 		if (ret && ret != -ENOSPC)
-			goto error;
+			return ret;
 
 		if (ret == 0)
-			max_avail = ctl.max_stripe_size * ctl.dev_stripes;
+			max_avail = dev_extent_want;
 
-		if (max_avail < BTRFS_STRIPE_LEN * ctl.dev_stripes) {
+		if (max_avail < dev_extent_min) {
 			if (btrfs_test_opt(info, ENOSPC_DEBUG))
 				btrfs_debug(info,
-			"%s: devid %llu has no free space, have=%llu want=%u",
+			"%s: devid %llu has no free space, have=%llu want=%llu",
 					    __func__, device->devid, max_avail,
-					    BTRFS_STRIPE_LEN * ctl.dev_stripes);
+					    dev_extent_min);
 			continue;
 		}
 
@@ -4968,14 +4932,63 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 		devices_info[ndevs].dev = device;
 		++ndevs;
 	}
-	ctl.ndevs = ndevs;
+	ctl->ndevs = ndevs;
 
 	/*
 	 * now sort the devices by hole size / available space
 	 */
-	sort(devices_info, ctl.ndevs, sizeof(struct btrfs_device_info),
+	sort(devices_info, ndevs, sizeof(struct btrfs_device_info),
 	     btrfs_cmp_device_info, NULL);
 
+	return 0;
+}
+
+static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
+			       u64 start, u64 type)
+{
+	struct btrfs_fs_info *info = trans->fs_info;
+	struct btrfs_fs_devices *fs_devices = info->fs_devices;
+	struct map_lookup *map = NULL;
+	struct extent_map_tree *em_tree;
+	struct extent_map *em;
+	struct btrfs_device_info *devices_info = NULL;
+	struct alloc_chunk_ctl ctl;
+	/* Number of stripes that count for block group size */
+	int data_stripes;
+	int ret;
+	int i;
+	int j;
+
+	if (!alloc_profile_is_valid(type, 0)) {
+		ASSERT(0);
+		return -EINVAL;
+	}
+
+	if (list_empty(&fs_devices->alloc_list)) {
+		if (btrfs_test_opt(info, ENOSPC_DEBUG))
+			btrfs_debug(info, "%s: no writable device", __func__);
+		return -ENOSPC;
+	}
+
+	if (!(type & BTRFS_BLOCK_GROUP_TYPE_MASK)) {
+		btrfs_err(info, "invalid chunk type 0x%llx requested", type);
+		ASSERT(0);
+		return -EINVAL;
+	}
+
+	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);
+	if (!devices_info)
+		return -ENOMEM;
+
+	ret = gather_device_info(fs_devices, &ctl, devices_info);
+	if (ret < 0)
+		goto error;
+
 	/*
 	 * Round down to number of usable stripes, devs_increment can be any
 	 * number so we can't use round_down()