We've avoided data losing raid profile when doing balance, but it
turns out that deleting a device could also result in the same
problem.
This fixes the problem by creating an empty data chunk before
relocating the data chunk.
Metadata/System chunk are supposed to have non-zero bytes all the time
so their raid profile is persistent.
Reported-by: James Alandt <James.Alandt@xxxxxxx>
Signed-off-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
---
fs/btrfs/volumes.c | 87 ++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 68 insertions(+), 19 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 4a72c45..3f48bcd 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -144,6 +144,8 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
u64 logical, u64 *length,
struct btrfs_bio **bbio_ret,
int mirror_num, int need_raid_map);
+static int btrfs_may_alloc_data_chunk(struct btrfs_fs_info *fs_info,
+ u64 chunk_offset);
DEFINE_MUTEX(uuid_mutex);
static LIST_HEAD(fs_uuids);
@@ -3476,7 +3478,6 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
u32 count_meta = 0;
u32 count_sys = 0;
int chunk_reserved = 0;
- u64 bytes_used = 0;
/* step one make some room on all the devices */
devices = &fs_info->fs_devices->devices;
@@ -3635,28 +3636,22 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
goto loop;
}
- ASSERT(fs_info->data_sinfo);
- spin_lock(&fs_info->data_sinfo->lock);
- bytes_used = fs_info->data_sinfo->bytes_used;
- spin_unlock(&fs_info->data_sinfo->lock);
-
- if ((chunk_type & BTRFS_BLOCK_GROUP_DATA) &&
- !chunk_reserved && !bytes_used) {
- 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, fs_info,
- BTRFS_BLOCK_GROUP_DATA);
- btrfs_end_transaction(trans);
+ if (!chunk_reserved) {
+ /*
+ * We may be relocating the only data chunk we have,
+ * which could potentially end up with losing data's
+ * raid profile, so lets allocate an empty one in
+ * advance.
+ */
+ ret = btrfs_may_alloc_data_chunk(fs_info,
+ found_key.offset);
if (ret < 0) {
mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+ ret = PTR_ERR(trans);
goto error;
+ } else if (ret == 1) {
+ chunk_reserved = 1;
}
- chunk_reserved = 1;
}
ret = btrfs_relocate_chunk(fs_info, found_key.offset);
@@ -4327,6 +4322,48 @@ int btrfs_check_uuid_tree(struct btrfs_fs_info *fs_info)
}
/*
+ * return 1 : allocate a data chunk successfully,
+ * return <0: errors during allocating a data chunk,
+ * return 0 : no need to allocate a data chunk.
+ */
+static int btrfs_may_alloc_data_chunk(struct btrfs_fs_info *fs_info,
+ u64 chunk_offset)
+{
+ struct btrfs_block_group_cache *cache;
+ u64 bytes_used;
+ u64 chunk_type;
+
+ cache = btrfs_lookup_block_group(fs_info, chunk_offset);
+ ASSERT(cache);
+ chunk_type = cache->flags;
+ btrfs_put_block_group(cache);
+
+ if (chunk_type & BTRFS_BLOCK_GROUP_DATA) {
+ spin_lock(&fs_info->data_sinfo->lock);
+ bytes_used = fs_info->data_sinfo->bytes_used;
+ spin_unlock(&fs_info->data_sinfo->lock);
+
+ if (!bytes_used) {
+ struct btrfs_trans_handle *trans;
+ int ret;
+
+ trans = btrfs_join_transaction(fs_info->tree_root);
+ if (IS_ERR(trans))
+ return PTR_ERR(trans);
+
+ ret = btrfs_force_chunk_alloc(trans, fs_info,
+ BTRFS_BLOCK_GROUP_DATA);
+ btrfs_end_transaction(trans);
+ if (ret < 0)
+ return ret;
+
+ return 1;
+ }
+ }
+ return 0;
+}
+
+/*
* shrinking a device means finding all of the device extents past
* the new size, and then following the back refs to the chunks.
* The chunk relocation code actually frees the device extent
@@ -4419,6 +4456,18 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
chunk_offset = btrfs_dev_extent_chunk_offset(l, dev_extent);
btrfs_release_path(path);
+ /*
+ * We may be relocating the only data chunk we have,
+ * which could potentially end up with losing data's
+ * raid profile, so lets allocate an empty one in
+ * advance.
+ */
+ ret = btrfs_may_alloc_data_chunk(fs_info, chunk_offset);
+ if (ret < 0) {
+ mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+ goto done;
+ }
+
ret = btrfs_relocate_chunk(fs_info, chunk_offset);
mutex_unlock(&fs_info->delete_unused_bgs_mutex);
if (ret && ret != -ENOSPC)
--
2.9.4
