On 2017年11月21日 12:06, Chris Murphy wrote: > On Mon, Nov 20, 2017 at 6:16 PM, Qu Wenruo <quwenruo.bt...@gmx.com> 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.bt...@gmx.com> 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.bt...@gmx.com> 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? ------ 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
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