On 10.12.2019 02:19 Qu Wenruo wrote:
>
> On 2019/12/10 上午8:52, Qu Wenruo wrote:
>>
>> On 2019/12/10 上午2:56, Martin Raiber wrote:
>>> On 07.12.2019 08:28 Qu Wenruo wrote:
>>>> On 2019/12/7 上午5:26, Martin Raiber wrote:
>>>>> Hi,
>>>>>
>>>>> with kernel 5.4.1 I have the problem that df shows 100% space used. I
>>>>> can still write to the btrfs volume, but my software looks at the
>>>>> available space and starts deleting stuff if statfs() says there is a
>>>>> low amount of available space.
>>>> If the bug still happens, mind to try the snippet to see why this happened?
>>>>
>>>> You will need to:
>>>> - Apply the patch to your kernel code
>>>> - Recompile the kernel or btrfs module
>>>> So this needs some experience in kernel compile.
>>>> - Reboot to newly compiled kernel or load the debug btrfs module
>>>>
>>>> Thanks,
>>>> Qu
>>>>
>>>> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
>>>> index 23aa630f04c9..cf34c05b16d7 100644
>>>> --- a/fs/btrfs/relocation.c
>>>> +++ b/fs/btrfs/relocation.c
>>>> @@ -523,7 +523,8 @@ static int should_ignore_root(struct btrfs_root *root)
>>>> {
>>>> struct btrfs_root *reloc_root;
>>>>
>>>> - if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
>>>> + if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||
>>>> + test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state))
>>>> return 0;
>>>>
>>>> reloc_root = root->reloc_root;
>>>> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>>>> index f452a94abdc3..c2b70d97a63b 100644
>>>> --- a/fs/btrfs/super.c
>>>> +++ b/fs/btrfs/super.c
>>>> @@ -2064,6 +2064,8 @@ static int btrfs_statfs(struct dentry *dentry,
>>>> struct kstatfs *buf)
>>>> found->disk_used;
>>>> }
>>>>
>>>> + pr_info("%s: found type=0x%llx disk_used=%llu factor=%d\n",
>>>> + __func__, found->flags, found->disk_used, factor);
>>>> total_used += found->disk_used;
>>>> }
>>>>
>>>> @@ -2071,6 +2073,8 @@ static int btrfs_statfs(struct dentry *dentry,
>>>> struct kstatfs *buf)
>>>>
>>>> buf->f_blocks = div_u64(btrfs_super_total_bytes(disk_super),
>>>> factor);
>>>> buf->f_blocks >>= bits;
>>>> + pr_info("%s: super_total_bytes=%llu total_used=%llu
>>>> factor=%d\n", __func__,
>>>> + btrfs_super_total_bytes(disk_super), total_used, factor);
>>>> buf->f_bfree = buf->f_blocks - (div_u64(total_used, factor) >>
>>>> bits);
>>>>
>>>> /* Account global block reserve as used, it's in logical size
>>>> already */
>>>>
>>> Applied. It's currently 100% used directly after reboot, and I am
>>> getting this log output:
>> Thank you a lot for the debug output!
>>
>>> [...]
>>> [ 241.245150] btrfs_statfs: super_total_bytes=128835387392
>>> total_used=93778841600 factor=1
>>> [ 241.904824] btrfs_statfs: found type=0x1 disk_used=93464006656 factor=1
>>> [ 241.904824] btrfs_statfs: found type=0x4 disk_used=314818560 factor=1
>>> [ 241.904824] btrfs_statfs: found type=0x2 disk_used=16384 factor=1
>>> [ 241.904824] btrfs_statfs: super_total_bytes=128835387392
>>> total_used=93778841600 factor=1
>> This proves the on-disk numbers are all correct, so far so good.
>>
>> The remaining problem is the block_rsv part. Which matches with the new
>> ticket system introduced in v5.4.
>>
>> Mind to test the new debug snippet?
>>
>> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>> index f452a94abdc3..516969534095 100644
>> --- a/fs/btrfs/super.c
>> +++ b/fs/btrfs/super.c
>> @@ -2076,6 +2076,8 @@ static int btrfs_statfs(struct dentry *dentry,
>> struct kstatfs *buf)
>> /* Account global block reserve as used, it's in logical size
>> already */
>> spin_lock(&block_rsv->lock);
>> /* Mixed block groups accounting is not byte-accurate, avoid
>> overflow */
>> + pr_info("%s: block_rsv->size=%llu block_rsv->reserved=%llu\n",
>> __func__,
>> + block_rsv->size, block_rsv->reserved);
>> if (buf->f_bfree >= block_rsv->size >> bits)
>> buf->f_bfree -= block_rsv->size >> bits;
>> else
>>
> And this extra snippet for available space.
>
> Thanks,
> Qu
>
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index f452a94abdc3..f1a3e01a0ef5 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -1911,6 +1911,7 @@ static inline int
> btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
> * We aren't under the device list lock, so this is racy-ish,
> but good
> * enough for our purposes.
> */
> + pr_info("%s: original_free_bytes=%llu\n", __func__, *free_bytes);
> nr_devices = fs_info->fs_devices->open_devices;
> if (!nr_devices) {
> smp_mb();
> @@ -2005,6 +2006,7 @@ static inline int
> btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
>
> kfree(devices_info);
> *free_bytes = avail_space;
> + pr_info("%s: calculated_bytes=%llu\n", __func__, avail_space);
> return 0;
> }
>
Now logs this at 100% used:
[90273.353449] btrfs_calc_avail_data_space: original_free_bytes=23583420416
[90273.353449] btrfs_calc_avail_data_space: calculated_bytes=13662945280
[90273.369508] btrfs_statfs: found type=0x1 disk_used=90233212928 factor=1
[90273.369536] btrfs_statfs: found type=0x1 disk_used=90233212928 factor=1
[90273.369536] btrfs_statfs: found type=0x4 disk_used=339361792 factor=1
[90273.369508] btrfs_statfs: found type=0x4 disk_used=339361792 factor=1
[90273.369508] btrfs_statfs: found type=0x2 disk_used=16384 factor=1
[90273.369536] btrfs_statfs: found type=0x2 disk_used=16384 factor=1
[90273.369508] btrfs_statfs: super_total_bytes=128835387392
total_used=90572591104 factor=1
[90273.369508] btrfs_statfs: block_rsv->size=147554304
block_rsv->reserved=147554304
[90273.369537] btrfs_statfs: super_total_bytes=128835387392
total_used=90572591104 factor=1
[90273.369509] btrfs_calc_avail_data_space: original_free_bytes=23583420416
[90273.369537] btrfs_statfs: block_rsv->size=147554304
block_rsv->reserved=147554304
[90273.369537] btrfs_calc_avail_data_space: original_free_bytes=23583420416
[90273.369509] btrfs_calc_avail_data_space: calculated_bytes=13662945280
[90273.369537] btrfs_calc_avail_data_space: calculated_bytes=13662945280
[90273.400227] btrfs_statfs: found type=0x1 disk_used=726834307072 factor=1
[90273.400227] btrfs_statfs: found type=0x4 disk_used=4908548096 factor=1
[90273.400227] btrfs_statfs: found type=0x2 disk_used=98304 factor=1
[90273.400227] btrfs_statfs: super_total_bytes=8133881348096
total_used=731742953472 factor=1
[90273.400227] btrfs_statfs: block_rsv->size=536870912
block_rsv->reserved=536821760
[90273.400227] btrfs_calc_avail_data_space: original_free_bytes=1171038208
[90273.400227] btrfs_calc_avail_data_space: calculated_bytes=7400493613056
