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. -- Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html