On Wed, Sep 30, 2015 at 12:11 PM, Zhao Lei <zhaolei@xxxxxxxxxxxxxx> wrote:
> Reproduce:
> (In integration-4.3 branch)
>
> TEST_DEV=(/dev/vdg /dev/vdh)
> TEST_DIR=/mnt/tmp
>
> umount "$TEST_DEV" >/dev/null
> mkfs.btrfs -f -d raid1 "${TEST_DEV[@]}"
>
> mount -o nospace_cache "$TEST_DEV" "$TEST_DIR"
> btrfs balance start -dusage=0 $TEST_DIR
> btrfs filesystem usage $TEST_DIR
>
> dd if=/dev/zero of="$TEST_DIR"/file count=100
> btrfs filesystem usage $TEST_DIR
>
> Result:
> We can see "no data chunk" in first "btrfs filesystem usage":
> # btrfs filesystem usage $TEST_DIR
> Overall:
> ...
> Metadata,single: Size:8.00MiB, Used:0.00B
> /dev/vdg 8.00MiB
> Metadata,RAID1: Size:122.88MiB, Used:112.00KiB
> /dev/vdg 122.88MiB
> /dev/vdh 122.88MiB
> System,single: Size:4.00MiB, Used:0.00B
> /dev/vdg 4.00MiB
> System,RAID1: Size:8.00MiB, Used:16.00KiB
> /dev/vdg 8.00MiB
> /dev/vdh 8.00MiB
> Unallocated:
> /dev/vdg 1.06GiB
> /dev/vdh 1.07GiB
>
> And "data chunks changed from raid1 to single" in second
> "btrfs filesystem usage":
> # btrfs filesystem usage $TEST_DIR
> Overall:
> ...
> Data,single: Size:256.00MiB, Used:0.00B
> /dev/vdh 256.00MiB
> Metadata,single: Size:8.00MiB, Used:0.00B
> /dev/vdg 8.00MiB
> Metadata,RAID1: Size:122.88MiB, Used:112.00KiB
> /dev/vdg 122.88MiB
> /dev/vdh 122.88MiB
> System,single: Size:4.00MiB, Used:0.00B
> /dev/vdg 4.00MiB
> System,RAID1: Size:8.00MiB, Used:16.00KiB
> /dev/vdg 8.00MiB
> /dev/vdh 8.00MiB
> Unallocated:
> /dev/vdg 1.06GiB
> /dev/vdh 841.92MiB
>
> Reason:
> btrfs balance delete last data chunk in case of no data in
> the filesystem, then we can see "no data chunk" by "fi usage"
> command.
>
> And when we do write operation to fs, the only available data
> profile is 0x0, result is all new chunks are allocated single type.
>
> Fix:
> Allocate a data chunk explicitly to ensure we don't lose the
> raid profile for data.
>
> Test:
> Test by above script, and confirmed the logic by debug output.
>
> Changelog v1->v2:
> 1: Update patch description of "Fix" field
> 2: Use BTRFS_BLOCK_GROUP_DATA for btrfs_force_chunk_alloc instead
> of 1
> 3: Only reserve chunk if balance data chunk.
> All suggested-by: Filipe Manana <fdmanana@xxxxxxxxx>
>
> Signed-off-by: Zhao Lei <zhaolei@xxxxxxxxxxxxxx>
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
thanks
> ---
> fs/btrfs/volumes.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 6fc73586..cd9e5bd 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -3277,6 +3277,7 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
> u64 limit_data = bctl->data.limit;
> u64 limit_meta = bctl->meta.limit;
> u64 limit_sys = bctl->sys.limit;
> + int chunk_reserved = 0;
>
> /* step one make some room on all the devices */
> devices = &fs_info->fs_devices->devices;
> @@ -3326,6 +3327,8 @@ again:
> key.type = BTRFS_CHUNK_ITEM_KEY;
>
> while (1) {
> + u64 chunk_type;
> +
> if ((!counting && atomic_read(&fs_info->balance_pause_req)) ||
> atomic_read(&fs_info->balance_cancel_req)) {
> ret = -ECANCELED;
> @@ -3371,8 +3374,10 @@ again:
> spin_unlock(&fs_info->balance_lock);
> }
>
> + chunk_type = btrfs_chunk_type(leaf, chunk);
> ret = should_balance_chunk(chunk_root, leaf, chunk,
> found_key.offset);
> +
> btrfs_release_path(path);
> if (!ret) {
> mutex_unlock(&fs_info->delete_unused_bgs_mutex);
> @@ -3387,6 +3392,25 @@ again:
> goto loop;
> }
>
> + if ((chunk_type & BTRFS_BLOCK_GROUP_DATA) && !chunk_reserved) {
> + trans = btrfs_start_transaction(chunk_root, 0);
> + if (IS_ERR(trans)) {
> + mutex_unlock(&fs_info->delete_unused_bgs_mutex);
> + ret = PTR_ERR(trans);
> + goto error;
> + }
> +
> + ret = btrfs_force_chunk_alloc(trans, chunk_root,
> + BTRFS_BLOCK_GROUP_DATA);
> + if (ret < 0) {
> + mutex_unlock(&fs_info->delete_unused_bgs_mutex);
> + goto error;
> + }
> +
> + btrfs_end_transaction(trans, chunk_root);
> + chunk_reserved = 1;
> + }
> +
> ret = btrfs_relocate_chunk(chunk_root,
> found_key.offset);
> mutex_unlock(&fs_info->delete_unused_bgs_mutex);
> --
> 1.8.5.1
>
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--
Filipe David Manana,
"Reasonable men adapt themselves to the world.
Unreasonable men adapt the world to themselves.
That's why all progress depends on unreasonable men."
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