Miao Xie
2012-Jan-17 10:03 UTC
[RFC][PATCH 2/2] Btrfs: change the calculation of available space since the data profile can be degenerated
Since the data profile can be degenerated(RAID10 -> RAID1 -> DUP, RAID0
->
SINGLE), btrfs can utilize almost the whole disk space, we can simplify the
calculation of the available space in btrfs_statfs(). The new method just
ignore the disk space(one BTRFS_STRIPE_LEN at most) that can not be used to
allocate a DUP chunk, the other space will be considered as the available
space, and be count.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
fs/btrfs/super.c | 105 +++++++++++------------------------------------------
1 files changed, 22 insertions(+), 83 deletions(-)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 34a8b61..0284620 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1039,32 +1039,6 @@ static int btrfs_remount(struct super_block *sb, int
*flags, char *data)
return 0;
}
-/* Used to sort the devices by max_avail(descending sort) */
-static int btrfs_cmp_device_free_bytes(const void *dev_info1,
- const void *dev_info2)
-{
- if (((struct btrfs_device_info *)dev_info1)->max_avail >
- ((struct btrfs_device_info *)dev_info2)->max_avail)
- return -1;
- else if (((struct btrfs_device_info *)dev_info1)->max_avail <
- ((struct btrfs_device_info *)dev_info2)->max_avail)
- return 1;
- else
- return 0;
-}
-
-/*
- * sort the devices by max_avail, in which max free extent size of each device
- * is stored.(Descending Sort)
- */
-static inline void btrfs_descending_sort_devices(
- struct btrfs_device_info *devices,
- size_t nr_devices)
-{
- sort(devices, nr_devices, sizeof(struct btrfs_device_info),
- btrfs_cmp_device_free_bytes, NULL);
-}
-
/*
* The helper to calc the free space on the devices that can be used to store
* file data.
@@ -1072,7 +1046,6 @@ static inline void btrfs_descending_sort_devices(
static int btrfs_calc_avail_data_space(struct btrfs_root *root, u64
*free_bytes)
{
struct btrfs_fs_info *fs_info = root->fs_info;
- struct btrfs_device_info *devices_info;
struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
struct btrfs_device *device;
u64 skip_space;
@@ -1080,31 +1053,12 @@ static int btrfs_calc_avail_data_space(struct btrfs_root
*root, u64 *free_bytes)
u64 avail_space;
u64 used_space;
u64 min_stripe_size;
- int min_stripes = 1, num_stripes = 1;
- int i = 0, nr_devices;
int ret;
- nr_devices = fs_info->fs_devices->open_devices;
- BUG_ON(!nr_devices);
-
- devices_info = kmalloc(sizeof(*devices_info) * nr_devices,
- GFP_NOFS);
- if (!devices_info)
- return -ENOMEM;
+ *free_bytes = 0;
/* calc min stripe number for data space alloction */
type = btrfs_get_alloc_profile(root, 1);
- if (type & BTRFS_BLOCK_GROUP_RAID0) {
- min_stripes = 2;
- num_stripes = nr_devices;
- } else if (type & BTRFS_BLOCK_GROUP_RAID1) {
- min_stripes = 2;
- num_stripes = 2;
- } else if (type & BTRFS_BLOCK_GROUP_RAID10) {
- min_stripes = 4;
- num_stripes = 4;
- }
-
if (type & BTRFS_BLOCK_GROUP_DUP)
min_stripe_size = 2 * BTRFS_STRIPE_LEN;
else
@@ -1117,8 +1071,7 @@ static int btrfs_calc_avail_data_space(struct btrfs_root
*root, u64 *free_bytes)
avail_space = device->total_bytes - device->bytes_used;
/* align with stripe_len */
- do_div(avail_space, BTRFS_STRIPE_LEN);
- avail_space *= BTRFS_STRIPE_LEN;
+ avail_space = round_down(avail_space, BTRFS_STRIPE_LEN);
/*
* In order to avoid overwritting the superblock on the drive,
@@ -1139,10 +1092,8 @@ static int btrfs_calc_avail_data_space(struct btrfs_root
*root, u64 *free_bytes)
*/
ret = btrfs_account_dev_extents_size(device, 0, skip_space - 1,
&used_space);
- if (ret) {
- kfree(devices_info);
+ if (ret)
return ret;
- }
/* calc the free space in [0, skip_space - 1] */
skip_space -= used_space;
@@ -1156,40 +1107,28 @@ static int btrfs_calc_avail_data_space(struct btrfs_root
*root, u64 *free_bytes)
else
avail_space = 0;
- if (avail_space < min_stripe_size)
- continue;
-
- devices_info[i].dev = device;
- devices_info[i].max_avail = avail_space;
-
- i++;
+ avail_space = round_down(avail_space, min_stripe_size);
+ *free_bytes += avail_space;
}
- nr_devices = i;
-
- btrfs_descending_sort_devices(devices_info, nr_devices);
-
- i = nr_devices - 1;
- avail_space = 0;
- while (nr_devices >= min_stripes) {
- if (num_stripes > nr_devices)
- num_stripes = nr_devices;
-
- if (devices_info[i].max_avail >= min_stripe_size) {
- int j;
- u64 alloc_size;
-
- avail_space += devices_info[i].max_avail * num_stripes;
- alloc_size = devices_info[i].max_avail;
- for (j = i + 1 - num_stripes; j <= i; j++)
- devices_info[j].max_avail -= alloc_size;
- }
- i--;
- nr_devices--;
- }
+ /*
+ * If there is no enough disk space for new RAID chunk allocation,
+ * the chunk allocator will degenerate the profile:
+ * RAID0 -> SINGLE
+ * RAID10 -> RAID1 -> DUP
+ *
+ * So if the profile is RAID0, the profile will be degenerated to
+ * SINGLE at last, and we can utilize the whole free disk space.
+ * Note: aligned with BTRFS_STRIPE_LEN, it is dealt with above, we
+ * needn''t do anything here.
+ *
+ * If the profile is RAID1 or RAID10, the profile will be DUP at last.
+ * So the free size must be even times BTRFS_STRIPE_LEN.
+ */
+ if (type & (BTRFS_BLOCK_GROUP_RAID1 |
+ BTRFS_BLOCK_GROUP_RAID10))
+ *free_bytes = round_down(*free_bytes, 2 * BTRFS_STRIPE_LEN);
- kfree(devices_info);
- *free_bytes = avail_space;
return 0;
}
--
1.7.6.5
--
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