On 2019/6/19 下午2:32, Nikolay Borisov wrote:
>
>
> On 25.05.19 г. 2:32 ч., Qu Wenruo wrote:
>> [BUG]
>> There is a bug report of unexpected ENOSPC from btrfs-convert.
>> https://github.com/kdave/btrfs-progs/issues/123#
>>
>> After some debug, even when we have enough unallocated space, we still
>> hit ENOSPC at btrfs_reserve_extent().
>>
>> [CAUSE]
>> Btrfs-progs relies on chunk preallocator to make enough space for
>> data/metadata.
>>
>> However after the introduction of delayed-ref, it's no longer reliable
>> to relie on btrfs_space_info::bytes_used and
>> btrfs_space_info::bytes_pinned to calculate used metadata space.
>>
>> For a running transaction with a lot of allocated tree blocks,
>> btrfs_space_info::bytes_used stays its original value, and will only be
>> updated when running delayed ref.
>>
>> This makes btrfs-progs chunk preallocator completely useless. And for
>> btrfs-convert/mkfs.btrfs --rootdir, if we're going to have enough
>> metadata to fill a metadata block group in one transaction, we will hit
>> ENOSPC no matter whether we have enough unallocated space.
>>
>> [FIX]
>> This patch will introduce btrfs_space_info::bytes_reserved to trace how
>> many space we have reserved but not yet committed to extent tree.
>>
>> To support this change, this commit also introduces the following
>> modification:
>> - More comment on btrfs_space_info::bytes_*
>> To make code a little easier to read
>>
>> - Export update_space_info() to preallocate empty data/metadata space
>> info for mkfs.
>> For mkfs, we only have a temporary fs image with SYSTEM chunk only.
>> Export update_space_info() so that we can preallocate empty
>> data/metadata space info before we start a transaction.
>>
>> - Proper btrfs_space_info::bytes_reserved update
>> The timing is the as kernel (except we don't need to update
>> bytes_reserved for data extents)
>> * Increase bytes_reserved when call alloc_reserved_tree_block()
>> * Decrease bytes_reserved when running delayed refs
>> With the help of head->must_insert_reserved to determine whether we
>> need to decrease.
>
> This text is opposite to what the code is doing. At the time of
> alloc_reserved_tree_block we actually decrement bytes_reserved since the
> allocated block is going to be added to bytes_used via
> update_block_group. This is done when delayed refs are being run.
My bad. I selected wrong alloc_* completion item for the increase part.
The increase is at alloc_tree_block().
The decrease part is correct, it's alloc_reserved_tree_block() which get
called at run delayed ref time.
I skipped several function call names in the call chain as I thought
it's obvious at patch write time, but not so obvious when re-viewing
this comment.
Thanks,
Qu
>
> At alloc_tree_block you increment bytes_reserved since this is the time
> when space for the extent is reserved.
>
>>
>> Issue: #123
>> Signed-off-by: Qu Wenruo <w...@suse.com>
>> ---
>> ctree.h | 24 ++++++++++++++++++++++++
>> extent-tree.c | 43 +++++++++++++++++++++++++++++++++++++------
>> mkfs/main.c | 11 +++++++++++
>> transaction.c | 8 ++++++++
>> 4 files changed, 80 insertions(+), 6 deletions(-)
>>
>> diff --git a/ctree.h b/ctree.h
>> index 76f52b1c9b08..93f96a578f2c 100644
>> --- a/ctree.h
>> +++ b/ctree.h
>> @@ -1060,8 +1060,29 @@ struct btrfs_qgroup_limit_item {
>> struct btrfs_space_info {
>> u64 flags;
>> u64 total_bytes;
>> + /*
>> + * Space already used.
>> + * Only accounting space in current extent tree, thus delayed ref
>> + * won't be accounted here.
>> + */
>> u64 bytes_used;
>> +
>> + /*
>> + * Space being pinned down.
>> + * So extent allocator will not try to allocate space from them.
>> + *
>> + * For cases like extents being freed in current transaction, or
>> + * manually pinned bytes for re-initializing certain trees.
>> + */
>> u64 bytes_pinned;
>> +
>> + /*
>> + * Space being reserved.
>> + * Space has already being reserved but not yet reach extent tree.
>> + *
>> + * New tree blocks allocated in current transaction goes here.
>> + */
>> + u64 bytes_reserved;
>> int full;
>> struct list_head list;
>> };
>> @@ -2528,6 +2549,9 @@ int btrfs_update_extent_ref(struct btrfs_trans_handle
>> *trans,
>> u64 root_objectid, u64 ref_generation,
>> u64 owner_objectid);
>> int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans);
>> +int update_space_info(struct btrfs_fs_info *info, u64 flags,
>> + u64 total_bytes, u64 bytes_used,
>> + struct btrfs_space_info **space_info);
>> int btrfs_free_block_groups(struct btrfs_fs_info *info);
>> int btrfs_read_block_groups(struct btrfs_root *root);
>> struct btrfs_block_group_cache *
>> diff --git a/extent-tree.c b/extent-tree.c
>> index e62ee8c2ba13..c7ca49bccd8b 100644
>> --- a/extent-tree.c
>> +++ b/extent-tree.c
>> @@ -1786,9 +1786,9 @@ static int free_space_info(struct btrfs_fs_info
>> *fs_info, u64 flags,
>> return 0;
>> }
>>
>> -static int update_space_info(struct btrfs_fs_info *info, u64 flags,
>> - u64 total_bytes, u64 bytes_used,
>> - struct btrfs_space_info **space_info)
>> +int update_space_info(struct btrfs_fs_info *info, u64 flags,
>> + u64 total_bytes, u64 bytes_used,
>> + struct btrfs_space_info **space_info)
>> {
>> struct btrfs_space_info *found;
>>
>> @@ -1814,6 +1814,7 @@ static int update_space_info(struct btrfs_fs_info
>> *info, u64 flags,
>> found->total_bytes = total_bytes;
>> found->bytes_used = bytes_used;
>> found->bytes_pinned = 0;
>> + found->bytes_reserved = 0;
>> found->full = 0;
>> *space_info = found;
>> return 0;
>> @@ -1859,8 +1860,8 @@ static int do_chunk_alloc(struct btrfs_trans_handle
>> *trans,
>> return 0;
>>
>> thresh = div_factor(space_info->total_bytes, 7);
>> - if ((space_info->bytes_used + space_info->bytes_pinned + alloc_bytes) <
>> - thresh)
>> + if ((space_info->bytes_used + space_info->bytes_pinned +
>> + space_info->bytes_reserved + alloc_bytes) < thresh)
>> return 0;
>>
>> /*
>> @@ -2538,6 +2539,7 @@ static int alloc_reserved_tree_block(struct
>> btrfs_trans_handle *trans,
>> struct btrfs_fs_info *fs_info = trans->fs_info;
>> struct btrfs_extent_item *extent_item;
>> struct btrfs_extent_inline_ref *iref;
>> + struct btrfs_space_info *sinfo;
>> struct extent_buffer *leaf;
>> struct btrfs_path *path;
>> struct btrfs_key ins;
>> @@ -2545,6 +2547,9 @@ static int alloc_reserved_tree_block(struct
>> btrfs_trans_handle *trans,
>> u64 start, end;
>> int ret;
>>
>> + sinfo = __find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
>> + ASSERT(sinfo);
>> +
>> ins.objectid = node->bytenr;
>> if (skinny_metadata) {
>> ins.offset = ref->level;
>> @@ -2605,6 +2610,14 @@ static int alloc_reserved_tree_block(struct
>> btrfs_trans_handle *trans,
>>
>> ret = update_block_group(fs_info, ins.objectid, fs_info->nodesize, 1,
>> 0);
>> + if (sinfo) {
>> + if (fs_info->nodesize > sinfo->bytes_reserved) {
>> + WARN_ON(1);
>> + sinfo->bytes_reserved = 0;
>> + } else {
>> + sinfo->bytes_reserved -= fs_info->nodesize;
>> + }
>> + }
>>
>> if (ref->root == BTRFS_EXTENT_TREE_OBJECTID) {
>> clear_extent_bits(&trans->fs_info->extent_ins, start, end,
>> @@ -2624,6 +2637,8 @@ static int alloc_tree_block(struct btrfs_trans_handle
>> *trans,
>> int ret;
>> u64 extent_size;
>> struct btrfs_delayed_extent_op *extent_op;
>> + struct btrfs_space_info *sinfo;
>> + struct btrfs_fs_info *fs_info = root->fs_info;
>> bool skinny_metadata = btrfs_fs_incompat(root->fs_info,
>> SKINNY_METADATA);
>>
>> @@ -2631,6 +2646,8 @@ static int alloc_tree_block(struct btrfs_trans_handle
>> *trans,
>> if (!extent_op)
>> return -ENOMEM;
>>
>> + sinfo = __find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
>> + ASSERT(sinfo);
>> ret = btrfs_reserve_extent(trans, root, num_bytes, empty_size,
>> hint_byte, search_end, ins, 0);
>> if (ret < 0)
>> @@ -2663,6 +2680,7 @@ static int alloc_tree_block(struct btrfs_trans_handle
>> *trans,
>> BUG_ON(ret);
>> }
>>
>> + sinfo->bytes_reserved += extent_size;
>> ret = btrfs_add_delayed_tree_ref(root->fs_info, trans, ins->objectid,
>> extent_size, 0, root_objectid,
>> level, BTRFS_ADD_DELAYED_EXTENT,
>> @@ -3000,6 +3018,10 @@ int btrfs_free_block_groups(struct btrfs_fs_info
>> *info)
>> sinfo = list_entry(info->space_info.next,
>> struct btrfs_space_info, list);
>> list_del_init(&sinfo->list);
>> + if (sinfo->bytes_reserved)
>> + warning(
>> + "reserved space leaked, flag=0x%llx bytes_reserved=%llu",
>> + sinfo->flags, sinfo->bytes_reserved);
>> kfree(sinfo);
>> }
>> return 0;
>> @@ -4106,8 +4128,17 @@ int cleanup_ref_head(struct btrfs_trans_handle *trans,
>> rb_erase(&head->href_node, &delayed_refs->href_root);
>> RB_CLEAR_NODE(&head->href_node);
>>
>> - if (head->must_insert_reserved)
>> + if (head->must_insert_reserved) {
>> btrfs_pin_extent(fs_info, head->bytenr, head->num_bytes);
>> + if (!head->is_data) {
>> + struct btrfs_space_info *sinfo;
>> +
>> + sinfo = __find_space_info(trans->fs_info,
>> + BTRFS_BLOCK_GROUP_METADATA);
>> + ASSERT(sinfo);
>> + sinfo->bytes_reserved -= head->num_bytes;
>> + }
>> + }
>>
>> btrfs_put_delayed_ref_head(head);
>> return 0;
>> diff --git a/mkfs/main.c b/mkfs/main.c
>> index b442e6e40c37..1d03ec52ddd6 100644
>> --- a/mkfs/main.c
>> +++ b/mkfs/main.c
>> @@ -58,11 +58,22 @@ static int create_metadata_block_groups(struct
>> btrfs_root *root, int mixed,
>> {
>> struct btrfs_fs_info *fs_info = root->fs_info;
>> struct btrfs_trans_handle *trans;
>> + struct btrfs_space_info *sinfo;
>> u64 bytes_used;
>> u64 chunk_start = 0;
>> u64 chunk_size = 0;
>> int ret;
>>
>> + /* Create needed space info to trace extents reservation */
>> + ret = update_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA,
>> + 0, 0, &sinfo);
>> + if (ret < 0)
>> + return ret;
>> + ret = update_space_info(fs_info, BTRFS_BLOCK_GROUP_DATA,
>> + 0, 0, &sinfo);
>> + if (ret < 0)
>> + return ret;
>> +
>> trans = btrfs_start_transaction(root, 1);
>> BUG_ON(IS_ERR(trans));
>> bytes_used = btrfs_super_bytes_used(fs_info->super_copy);
>> diff --git a/transaction.c b/transaction.c
>> index 138e10f0d6cc..d2c7f4829eda 100644
>> --- a/transaction.c
>> +++ b/transaction.c
>> @@ -158,6 +158,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle
>> *trans,
>> u64 transid = trans->transid;
>> int ret = 0;
>> struct btrfs_fs_info *fs_info = root->fs_info;
>> + struct btrfs_space_info *sinfo;
>>
>> if (trans->fs_info->transaction_aborted)
>> return -EROFS;
>> @@ -209,6 +210,13 @@ commit_tree:
>> root->commit_root = NULL;
>> fs_info->running_transaction = NULL;
>> fs_info->last_trans_committed = transid;
>> + list_for_each_entry(sinfo, &fs_info->space_info, list) {
>> + if (sinfo->bytes_reserved) {
>> + warning(
>> + "reserved space leaked, transid=%llu flag=0x%llx bytes_reserved=%llu",
>> + transid, sinfo->flags, sinfo->bytes_reserved);
>> + }
>> + }
>> return ret;
>> error:
>> btrfs_destroy_delayed_refs(trans);
>>
