On Mon, Nov 20, 2017 at 9:29 PM, Qu Wenruo <quwenruo.btrfs@xxxxxxx> wrote:
>
>
> On 2017年11月21日 12:06, Chris Murphy wrote:
>> On Mon, Nov 20, 2017 at 6:16 PM, Qu Wenruo <quwenruo.btrfs@xxxxxxx> wrote:
>>>
>>>
>>> On 2017年11月21日 06:23, Chris Murphy wrote:
>>>> On Sun, Nov 19, 2017 at 7:42 PM, Qu Wenruo <quwenruo.btrfs@xxxxxxx> wrote:
>>>>>
>>>>>
>>>>> On 2017年11月20日 10:24, Chris Murphy wrote:
>>>>>> On Sun, Nov 19, 2017 at 7:13 PM, Qu Wenruo <quwenruo.btrfs@xxxxxxx> wrote:
>>>>>>>
>>>>>>>
>>>>>>> On 2017年11月19日 14:17, Chris Murphy wrote:
>>>>>>>> fstrim should trim free space, but it only trims unallocated. This is
>>>>>>>> with kernel 4.14.0 and the entire 4.13 series. I'm pretty sure it
>>>>>>>> behaved this way with 4.12 also.
>>>>>>>
>>>>>>> Tested with 4.14-rc7, can't reproduce it.
>>>>>>
>>>>>> $ sudo btrfs fi us /
>>>>>> Overall:
>>>>>> Device size: 70.00GiB
>>>>>> Device allocated: 31.03GiB
>>>>>> Device unallocated: 38.97GiB
>>>>>> Device missing: 0.00B
>>>>>> Used: 22.12GiB
>>>>>> Free (estimated): 47.62GiB (min: 47.62GiB)
>>>>>> ...snip...
>>>>>>
>>>>>> $ sudo fstrim -v /
>>>>>> /: 39 GiB (41841328128 bytes) trimmed
>>>>>>
>>>>>> Then I run btrfs-debug -b / and find the least used block group, at 8% usage;
>>>>>>
>>>>>> block group offset 174202028032 len 1073741824 used 89206784
>>>>>> chunk_objectid 256 flags 1 usage 0.08
>>>>>>
>>>>>> And balance that block group:
>>>>>>
>>>>>> $ sudo btrfs balance start -dvrange=174202028032..174202028033 -dlimit=1 /
>>>>>> Done, had to relocate 1 out of 32 chunks
>>>>>>
>>>>>> And trim again:
>>>>>>
>>>>>> /: 39 GiB (41841328128 bytes) trimmed
>>>>>>
>>>>>>
>>>>>>> Any special mount options or setup?
>>>>>>> (BTW, I also tried space_cache=v2 and default v1, no obvious difference)
>>>>>>
>>>>>>
>>>>>> /dev/nvme0n1p8 on / type btrfs
>>>>>> (rw,relatime,seclabel,ssd,space_cache,subvolid=333,subvol=/root27)
>>>>>
>>>>> Nothing special at all.
>>>>>
>>>>> And unfortunately, no trace point inside btrfs_trim_block_group() at all.
>>>>>
>>>>> But a quick glance shows me that, the loop to iterate existing block
>>>>> groups to trim free space inside them has a return value overwrite bug.
>>>>>
>>>>> So only unallocated space get trimmed.
>>>>>
>>>>> Would you please try this diff to get the return value?
>>>>>
>>>>> ------
>>>>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>>>>> index 309a109069f1..dbec05dc8810 100644
>>>>> --- a/fs/btrfs/extent-tree.c
>>>>> +++ b/fs/btrfs/extent-tree.c
>>>>> @@ -10983,12 +10983,12 @@ int btrfs_trim_fs(struct btrfs_fs_info
>>>>> *fs_info, struct fstrim_range *range)
>>>>> ret = cache_block_group(cache, 0);
>>>>> if (ret) {
>>>>> btrfs_put_block_group(cache);
>>>>> - break;
>>>>> + goto out;
>>>>> }
>>>>> ret = wait_block_group_cache_done(cache);
>>>>> if (ret) {
>>>>> btrfs_put_block_group(cache);
>>>>> - break;
>>>>> + goto out;
>>>>> }
>>>>> }
>>>>> ret = btrfs_trim_block_group(cache,
>>>>> @@ -11000,7 +11000,7 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info,
>>>>> struct fstrim_range *range)
>>>>> trimmed += group_trimmed;
>>>>> if (ret) {
>>>>> btrfs_put_block_group(cache);
>>>>> - break;
>>>>> + goto out;
>>>>> }
>>>>> }
>>>>>
>>>>> @@ -11019,6 +11019,7 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info,
>>>>> struct fstrim_range *range)
>>>>> }
>>>>> mutex_unlock(&fs_info->fs_devices->device_list_mutex);
>>>>>
>>>>> +out:
>>>>> range->len = trimmed;
>>>>> return ret;
>>>>> }
>>>>> ------
>>>>
>>>> This won't apply on tag v4.14 for some reason.
>>>>
>>>> [chris@f27s linux]$ git apply -v ~/qutrim1.patch
>>>> Checking patch fs/btrfs/extent-tree.c...
>>>> error: while searching for:
>>>> ret = cache_block_group(cache, 0);
>>>> if (ret) {
>>>> btrfs_put_block_group(cache);
>>>> break;
>>>> }
>>>> ret = wait_block_group_cache_done(cache);
>>>> if (ret) {
>>>> btrfs_put_block_group(cache);
>>>> break;
>>>> }
>>>> }
>>>> ret = btrfs_trim_block_group(cache,
>>>>
>>>> error: patch failed: fs/btrfs/extent-tree.c:10983
>>>> error: fs/btrfs/extent-tree.c: patch does not apply
>>>> [chris@f27s linux]$
>>>>
>>>>
>>>> If I do it manually (just adding the goto and build it, reboot, I
>>>> still get the same result for fstrim and nothing in dmesg.
>>>
>>> Sorry, that diff will not output extra info. Just to abort the process
>>> and return true error code.
>>
>> OK? It didn't seem to do that either. I see no change.
>>
>>
>>>
>>> I have update the patch to output more verbose output.
>>> You could find it in patchwork:
>>> https://patchwork.kernel.org/patch/10065991/
>>
>> Patch applies on v4.14.0, and still nothing in dmesg, or in user space
>> when issuing fstrim.
>>
>> # fstrim -v /
>> /: 38 GiB (40767586304 bytes) trimmed
>> # dmesg | grep -i btrfs
>> [ 2.745902] btrfs: loading out-of-tree module taints kernel.
>> [ 2.749905] Btrfs loaded, crc32c=crc32c-intel
>> [ 2.751072] BTRFS: device label fedora devid 1 transid 252048 /dev/nvme0n1p8
>> [ 4.295891] BTRFS info (device nvme0n1p8): disk space caching is enabled
>> [ 4.295892] BTRFS info (device nvme0n1p8): has skinny extents
>> [ 4.307326] BTRFS info (device nvme0n1p8): enabling ssd optimizations
>> [ 4.959467] BTRFS info (device nvme0n1p8): disk space caching is enabled
>> [root@f27h ~]#
>>
>>
>> Pretty sure the patch is applied because of the first message about
>> the out of tree module, which I do not get with Fedora kernels.
>
> So that's not something wrong happened to make you skip trimming one
> chunk, but something else just skipped the block group trimming.
>
> And I don't think DEBUG config is related to this.
>
> I doubt if it's the @fstrim_range passed in has something strange that
> prevent us from trimming block groups.
>
> Would you please try this diff based on the patch from patchwork?
Apply in addition to previous patch? Or apply to clean v4.14?
>
> ------
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index f830aa91ac3d..a4bf29a4a860 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -10972,6 +10972,8 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info,
> struct fstrim_range *range)
> int dev_ret = 0;
> int ret = 0;
>
> + btrfs_info(fs_info, "trimming btrfs, start=%llu len=%llu
> minlen=%llu",
> + range->start, range->len, range->minlen);
> /*
> * try to trim all FS space, our block group may start from
> non-zero.
> */
> @@ -10981,6 +10983,8 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info,
> struct fstrim_range *range)
> cache = btrfs_lookup_block_group(fs_info, range->start);
>
> for (; cache; cache = next_block_group(fs_info, cache)) {
> + btrfs_info(fs_info, "bg start=%llu len=%llu",
> + cache->key.objectid, cache->key.offset);
> if (cache->key.objectid >= (range->start + range->len)) {
> btrfs_put_block_group(cache);
> break;
> @@ -11045,6 +11049,7 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info,
> struct fstrim_range *range)
> mutex_unlock(&fs_info->fs_devices->device_list_mutex);
>
> range->len = trimmed;
> + btrfs_info(fs_info, "trimming done");
> if (bg_ret)
> return bg_ret;
> return dev_ret;
>
> ------
>
> Thanks,
> Qu
>
--
Chris Murphy
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