On 2018年02月23日 16:14, Nikolay Borisov wrote:
>
>
> On 23.02.2018 01:34, Qu Wenruo wrote:
>>
>>
>> On 2018年02月23日 06:44, Jeff Mahoney wrote:
>>> On 12/22/17 1:18 AM, Qu Wenruo wrote:
>>>> Unlike reservation calculation used in inode rsv for metadata, qgroup
>>>> doesn't really need to care things like csum size or extent usage for
>>>> whole tree COW.
>>>>
>>>> Qgroup care more about net change of extent usage.
>>>> That's to say, if we're going to insert one file extent, it will mostly
>>>> find its place in CoWed tree block, leaving no change in extent usage.
>>>> Or cause leaf split, result one new net extent, increasing qgroup number
>>>> by nodesize.
>>>> (Or even more rare case, increase the tree level, increasing qgroup
>>>> number by 2 * nodesize)
>>>>
>>>> So here instead of using the way overkilled calculation for extent
>>>> allocator, which cares more about accurate and no error, qgroup doesn't
>>>> need that over-calculated reservation.
>>>>
>>>> This patch will maintain 2 new members in btrfs_block_rsv structure for
>>>> qgroup, using much smaller calculation for qgroup rsv, reducing false
>>>> EDQUOT.
>>>
>>>
>>> I think this is the right idea but, rather than being the last step in a
>>> qgroup rework, it should be the first.
>>
>> That's right.
>>
>> Although putting it as 1st patch needs extra work to co-operate with
>> later type seperation.
>>
>>> Don't qgroup reservation
>>> lifetimes match the block reservation lifetimes?
>>
>> Also correct, but...
>>
>>> We wouldn't want a
>>> global reserve and we wouldn't track usage on a per-block basis, but
>>> they should otherwise match. We already have clear APIs surrounding the
>>> use of block reservations, so it seems to me that it'd make sense to
>>> extend those to cover the qgroup cases as well. Otherwise, the rest of
>>> your patchset makes a parallel reservation system with a different API.
>>> That keeps the current state of qgroups as a bolt-on that always needs
>>> to be tracked separately (and which developers need to ensure they get
>>> right).
>>
>> The problem is, block reservation is designed to ensure every CoW could
>> be fulfilled without error.
>>
>> That's to say, for case like CoW write with csum, we need to care about
>> space reservation not only for EXTENT_DATA in fs tree, but also later
>> EXTENT_ITEM for extent tree, and CSUM_ITEM for csum tree.
>>
>> However extent tree and csum tree doesn't contribute to quota at all.
>> If we follow such over-reservation, it would be much much easier to hit
>> false EDQUOTA early.
>>
>> That's the main reason why a separate (and a little simplified) block
>> rsv tracking system.
>>
>> And if there is better solution, I'm all ears.
>
> So looking at the code the main hurdles seems to be the fact that the
> btrfs_block_rsv_* API's take a raw byte count, which is derived from
> btrfs_calc_trans_metadata_size, which in turn is passed the number of
> items we want.
>
> So what if we extend the block_rsv_* apis to take an additional
> 'quota_bytes' or somesuch argument which would represent the amount we
> would like to be charged to the qgroups. This will force us to revisit
> every call site of block_rsv API's and adjust the code accordingly so
> that callers pass the correct number. This will lead to code such as:
>
> if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) { blah }
We don't need to do such check at call site.
Just do the calculation (which should be really simple, as simple as
nodesize * nr_items_to_add), and pass it to btrfs_qgroup_reserve_* APIs,
which would handle the quota enabled check.
>
> be contained into the block rsv apis. This will ensure lifetime of
> blockrsv/qgroups is always consistent. I think this only applies to
> qgroup metadata reservations.
Yep, and only applies to PREALLOC type metadata reservation.
For per-transaction rsv, it's handled by PERTRANS type.
Thanks,
Qu
>
>
>
>
>>
>> Thanks,
>> Qu
>>
>>>
>>> -Jeff
>>>
>>>> Signed-off-by: Qu Wenruo <w...@suse.com>
>>>> ---
>>>> fs/btrfs/ctree.h | 18 +++++++++++++++++
>>>> fs/btrfs/extent-tree.c | 55
>>>> ++++++++++++++++++++++++++++++++++++++++----------
>>>> 2 files changed, 62 insertions(+), 11 deletions(-)
>>>>
>>>> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
>>>> index 0c58f92c2d44..97783ba91e00 100644
>>>> --- a/fs/btrfs/ctree.h
>>>> +++ b/fs/btrfs/ctree.h
>>>> @@ -467,6 +467,24 @@ struct btrfs_block_rsv {
>>>> unsigned short full;
>>>> unsigned short type;
>>>> unsigned short failfast;
>>>> +
>>>> + /*
>>>> + * Qgroup equivalent for @size @reserved
>>>> + *
>>>> + * Unlike normal normal @size/@reserved for inode rsv,
>>>> + * qgroup doesn't care about things like csum size nor how many tree
>>>> + * blocks it will need to reserve.
>>>> + *
>>>> + * Qgroup cares more about *NET* change of extent usage.
>>>> + * So for ONE newly inserted file extent, in worst case it will cause
>>>> + * leaf split and level increase, nodesize for each file extent
>>>> + * is already way overkilled.
>>>> + *
>>>> + * In short, qgroup_size/reserved is the up limit of possible needed
>>>> + * qgroup metadata reservation.
>>>> + */
>>>> + u64 qgroup_rsv_size;
>>>> + u64 qgroup_rsv_reserved;
>>>> };
>>>>
>>>> /*
>>>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>>>> index 986660f301de..9d579c7bcf7f 100644
>>>> --- a/fs/btrfs/extent-tree.c
>>>> +++ b/fs/btrfs/extent-tree.c
>>>> @@ -5565,14 +5565,18 @@ static void space_info_add_new_bytes(struct
>>>> btrfs_fs_info *fs_info,
>>>>
>>>> static u64 block_rsv_release_bytes(struct btrfs_fs_info *fs_info,
>>>> struct btrfs_block_rsv *block_rsv,
>>>> - struct btrfs_block_rsv *dest, u64 num_bytes)
>>>> + struct btrfs_block_rsv *dest, u64 num_bytes,
>>>> + u64 *qgroup_to_release_ret)
>>>> {
>>>> struct btrfs_space_info *space_info = block_rsv->space_info;
>>>> + u64 qgroup_to_release = 0;
>>>> u64 ret;
>>>>
>>>> spin_lock(&block_rsv->lock);
>>>> - if (num_bytes == (u64)-1)
>>>> + if (num_bytes == (u64)-1) {
>>>> num_bytes = block_rsv->size;
>>>> + qgroup_to_release = block_rsv->qgroup_rsv_size;
>>>> + }
>>>> block_rsv->size -= num_bytes;
>>>> if (block_rsv->reserved >= block_rsv->size) {
>>>> num_bytes = block_rsv->reserved - block_rsv->size;
>>>> @@ -5581,6 +5585,12 @@ static u64 block_rsv_release_bytes(struct
>>>> btrfs_fs_info *fs_info,
>>>> } else {
>>>> num_bytes = 0;
>>>> }
>>>> + if (block_rsv->qgroup_rsv_reserved >= block_rsv->qgroup_rsv_size) {
>>>> + qgroup_to_release = block_rsv->qgroup_rsv_reserved -
>>>> + block_rsv->qgroup_rsv_size;
>>>> + block_rsv->qgroup_rsv_reserved = block_rsv->qgroup_rsv_size;
>>>> + } else
>>>> + qgroup_to_release = 0;
>>>> spin_unlock(&block_rsv->lock);
>>>>
>>>> ret = num_bytes;
>>>> @@ -5603,6 +5613,8 @@ static u64 block_rsv_release_bytes(struct
>>>> btrfs_fs_info *fs_info,
>>>> space_info_add_old_bytes(fs_info, space_info,
>>>> num_bytes);
>>>> }
>>>> + if (qgroup_to_release_ret)
>>>> + *qgroup_to_release_ret = qgroup_to_release;
>>>> return ret;
>>>> }
>>>>
>>>> @@ -5744,17 +5756,21 @@ int btrfs_inode_rsv_refill(struct btrfs_inode
>>>> *inode,
>>>> struct btrfs_root *root = inode->root;
>>>> struct btrfs_block_rsv *block_rsv = &inode->block_rsv;
>>>> u64 num_bytes = 0;
>>>> + u64 qgroup_num_bytes = 0;
>>>> int ret = -ENOSPC;
>>>>
>>>> spin_lock(&block_rsv->lock);
>>>> if (block_rsv->reserved < block_rsv->size)
>>>> num_bytes = block_rsv->size - block_rsv->reserved;
>>>> + if (block_rsv->qgroup_rsv_reserved < block_rsv->qgroup_rsv_size)
>>>> + qgroup_num_bytes = block_rsv->qgroup_rsv_size -
>>>> + block_rsv->qgroup_rsv_reserved;
>>>> spin_unlock(&block_rsv->lock);
>>>>
>>>> if (num_bytes == 0)
>>>> return 0;
>>>>
>>>> - ret = btrfs_qgroup_reserve_meta_prealloc(root, num_bytes, true);
>>>> + ret = btrfs_qgroup_reserve_meta_prealloc(root, qgroup_num_bytes, true);
>>>> if (ret)
>>>> return ret;
>>>> ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush);
>>>> @@ -5762,7 +5778,13 @@ int btrfs_inode_rsv_refill(struct btrfs_inode
>>>> *inode,
>>>> block_rsv_add_bytes(block_rsv, num_bytes, 0);
>>>> trace_btrfs_space_reservation(root->fs_info, "delalloc",
>>>> btrfs_ino(inode), num_bytes, 1);
>>>> - }
>>>> +
>>>> + /* Don't forget to increase qgroup_rsv_reserved */
>>>> + spin_lock(&block_rsv->lock);
>>>> + block_rsv->qgroup_rsv_reserved += qgroup_num_bytes;
>>>> + spin_unlock(&block_rsv->lock);
>>>> + } else
>>>> + btrfs_qgroup_free_meta_prealloc(root, qgroup_num_bytes);
>>>> return ret;
>>>> }
>>>>
>>>> @@ -5784,20 +5806,23 @@ void btrfs_inode_rsv_release(struct btrfs_inode
>>>> *inode, bool qgroup_free)
>>>> struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
>>>> struct btrfs_block_rsv *block_rsv = &inode->block_rsv;
>>>> u64 released = 0;
>>>> + u64 qgroup_to_release = 0;
>>>>
>>>> /*
>>>> * Since we statically set the block_rsv->size we just want to say we
>>>> * are releasing 0 bytes, and then we'll just get the reservation over
>>>> * the size free'd.
>>>> */
>>>> - released = block_rsv_release_bytes(fs_info, block_rsv, global_rsv, 0);
>>>> + released = block_rsv_release_bytes(fs_info, block_rsv, global_rsv, 0,
>>>> + &qgroup_to_release);
>>>> if (released > 0)
>>>> trace_btrfs_space_reservation(fs_info, "delalloc",
>>>> btrfs_ino(inode), released, 0);
>>>> if (qgroup_free)
>>>> - btrfs_qgroup_free_meta_prealloc(inode->root, released);
>>>> + btrfs_qgroup_free_meta_prealloc(inode->root, qgroup_to_release);
>>>> else
>>>> - btrfs_qgroup_convert_reserved_meta(inode->root, released);
>>>> + btrfs_qgroup_convert_reserved_meta(inode->root,
>>>> + qgroup_to_release);
>>>> }
>>>>
>>>> void btrfs_block_rsv_release(struct btrfs_fs_info *fs_info,
>>>> @@ -5809,7 +5834,7 @@ void btrfs_block_rsv_release(struct btrfs_fs_info
>>>> *fs_info,
>>>> if (global_rsv == block_rsv ||
>>>> block_rsv->space_info != global_rsv->space_info)
>>>> global_rsv = NULL;
>>>> - block_rsv_release_bytes(fs_info, block_rsv, global_rsv, num_bytes);
>>>> + block_rsv_release_bytes(fs_info, block_rsv, global_rsv, num_bytes,
>>>> NULL);
>>>> }
>>>>
>>>> static void update_global_block_rsv(struct btrfs_fs_info *fs_info)
>>>> @@ -5889,7 +5914,7 @@ static void init_global_block_rsv(struct
>>>> btrfs_fs_info *fs_info)
>>>> static void release_global_block_rsv(struct btrfs_fs_info *fs_info)
>>>> {
>>>> block_rsv_release_bytes(fs_info, &fs_info->global_block_rsv, NULL,
>>>> - (u64)-1);
>>>> + (u64)-1, NULL);
>>>> WARN_ON(fs_info->trans_block_rsv.size > 0);
>>>> WARN_ON(fs_info->trans_block_rsv.reserved > 0);
>>>> WARN_ON(fs_info->chunk_block_rsv.size > 0);
>>>> @@ -5931,7 +5956,7 @@ void btrfs_trans_release_chunk_metadata(struct
>>>> btrfs_trans_handle *trans)
>>>> WARN_ON_ONCE(!list_empty(&trans->new_bgs));
>>>>
>>>> block_rsv_release_bytes(fs_info, &fs_info->chunk_block_rsv, NULL,
>>>> - trans->chunk_bytes_reserved);
>>>> + trans->chunk_bytes_reserved, NULL);
>>>> trans->chunk_bytes_reserved = 0;
>>>> }
>>>>
>>>> @@ -6036,6 +6061,7 @@ static void
>>>> btrfs_calculate_inode_block_rsv_size(struct btrfs_fs_info *fs_info,
>>>> {
>>>> struct btrfs_block_rsv *block_rsv = &inode->block_rsv;
>>>> u64 reserve_size = 0;
>>>> + u64 qgroup_rsv_size = 0;
>>>> u64 csum_leaves;
>>>> unsigned outstanding_extents;
>>>>
>>>> @@ -6048,9 +6074,16 @@ static void
>>>> btrfs_calculate_inode_block_rsv_size(struct btrfs_fs_info *fs_info,
>>>> inode->csum_bytes);
>>>> reserve_size += btrfs_calc_trans_metadata_size(fs_info,
>>>> csum_leaves);
>>>> + /*
>>>> + * For qgroup rsv, the calculation is very simple:
>>>> + * nodesize for each outstanding extent.
>>>> + * This is already overkilled under most case.
>>>> + */
>>>> + qgroup_rsv_size = outstanding_extents * fs_info->nodesize;
>>>>
>>>> spin_lock(&block_rsv->lock);
>>>> block_rsv->size = reserve_size;
>>>> + block_rsv->qgroup_rsv_size = qgroup_rsv_size;
>>>> spin_unlock(&block_rsv->lock);
>>>> }
>>>>
>>>> @@ -8405,7 +8438,7 @@ static void unuse_block_rsv(struct btrfs_fs_info
>>>> *fs_info,
>>>> struct btrfs_block_rsv *block_rsv, u32 blocksize)
>>>> {
>>>> block_rsv_add_bytes(block_rsv, blocksize, 0);
>>>> - block_rsv_release_bytes(fs_info, block_rsv, NULL, 0);
>>>> + block_rsv_release_bytes(fs_info, block_rsv, NULL, 0, NULL);
>>>> }
>>>>
>>>> /*
>>>>
>>>
>>>
>>
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