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;
}
------
Thanks,
Qu
>
>
> Would a strace of fstrim help?
>
>
Attachment:
signature.asc
Description: OpenPGP digital signature
