From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net ([212.227.17.21]:61939 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752330AbdKUE3a (ORCPT ); Mon, 20 Nov 2017 23:29:30 -0500 Subject: Re: bug? fstrim only trims unallocated space, not unused in bg's To: Chris Murphy Cc: Btrfs BTRFS References: <0f6c7514-1cf2-1d88-1307-c43f7642b525@gmx.com> From: Qu Wenruo Message-ID: Date: Tue, 21 Nov 2017 12:29:24 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="f6EVdbUss6DtGAub2xRbTeKVfdheuJikr" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --f6EVdbUss6DtGAub2xRbTeKVfdheuJikr Content-Type: multipart/mixed; boundary="ctsPUEpHmehDqnip1pFBentc0hMeCQXJa"; protected-headers="v1" From: Qu Wenruo To: Chris Murphy Cc: Btrfs BTRFS Message-ID: Subject: Re: bug? fstrim only trims unallocated space, not unused in bg's References: <0f6c7514-1cf2-1d88-1307-c43f7642b525@gmx.com> In-Reply-To: --ctsPUEpHmehDqnip1pFBentc0hMeCQXJa Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 2017=E5=B9=B411=E6=9C=8821=E6=97=A5 12:06, Chris Murphy wrote: > On Mon, Nov 20, 2017 at 6:16 PM, Qu Wenruo wro= te: >> >> >> On 2017=E5=B9=B411=E6=9C=8821=E6=97=A5 06:23, Chris Murphy wrote: >>> On Sun, Nov 19, 2017 at 7:42 PM, Qu Wenruo w= rote: >>>> >>>> >>>> On 2017=E5=B9=B411=E6=9C=8820=E6=97=A5 10:24, Chris Murphy wrote: >>>>> On Sun, Nov 19, 2017 at 7:13 PM, Qu Wenruo = wrote: >>>>>> >>>>>> >>>>>> On 2017=E5=B9=B411=E6=9C=8819=E6=97=A5 14:17, Chris Murphy wrote: >>>>>>> fstrim should trim free space, but it only trims unallocated. Thi= s 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=3D174202028032..174202028033 -d= limit=3D1 / >>>>> 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=3Dv2 and default v1, no obvious dif= ference) >>>>> >>>>> >>>>> /dev/nvme0n1p8 on / type btrfs >>>>> (rw,relatime,seclabel,ssd,space_cache,subvolid=3D333,subvol=3D/root= 27) >>>> >>>> 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 b= ug. >>>> >>>> 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 =3D cache_block_group(cache, 0);= >>>> if (ret) { >>>> btrfs_put_block_group(cache)= ; >>>> - break; >>>> + goto out; >>>> } >>>> ret =3D wait_block_group_cache_done(= cache); >>>> if (ret) { >>>> btrfs_put_block_group(cache)= ; >>>> - break; >>>> + goto out; >>>> } >>>> } >>>> ret =3D btrfs_trim_block_group(cache, >>>> @@ -11000,7 +11000,7 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_i= nfo, >>>> struct fstrim_range *range) >>>> trimmed +=3D 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_i= nfo, >>>> struct fstrim_range *range) >>>> } >>>> mutex_unlock(&fs_info->fs_devices->device_list_mutex); >>>> >>>> +out: >>>> range->len =3D 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 =3D cache_block_group(cache, 0); >>> if (ret) { >>> btrfs_put_block_group(cache); >>> break; >>> } >>> ret =3D wait_block_group_cache_done(ca= che); >>> if (ret) { >>> btrfs_put_block_group(cache); >>> break; >>> } >>> } >>> ret =3D 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. >=20 > OK? It didn't seem to do that either. I see no change. >=20 >=20 >> >> I have update the patch to output more verbose output. >> You could find it in patchwork: >> https://patchwork.kernel.org/patch/10065991/ >=20 > Patch applies on v4.14.0, and still nothing in dmesg, or in user space > when issuing fstrim. >=20 > # 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=3Dcrc32c-intel > [ 2.751072] BTRFS: device label fedora devid 1 transid 252048 /dev/n= vme0n1p8 > [ 4.295891] BTRFS info (device nvme0n1p8): disk space caching is ena= bled > [ 4.295892] BTRFS info (device nvme0n1p8): has skinny extents > [ 4.307326] BTRFS info (device nvme0n1p8): enabling ssd optimization= s > [ 4.959467] BTRFS info (device nvme0n1p8): disk space caching is ena= bled > [root@f27h ~]# >=20 >=20 > 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 =3D 0; int ret =3D 0; + btrfs_info(fs_info, "trimming btrfs, start=3D%llu len=3D%llu minlen=3D%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 =3D btrfs_lookup_block_group(fs_info, range->start)= ; for (; cache; cache =3D next_block_group(fs_info, cache)) { + btrfs_info(fs_info, "bg start=3D%llu len=3D%llu", + cache->key.objectid, cache->key.offset); if (cache->key.objectid >=3D (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 =3D trimmed; + btrfs_info(fs_info, "trimming done"); if (bg_ret) return bg_ret; return dev_ret; ------ Thanks, Qu --ctsPUEpHmehDqnip1pFBentc0hMeCQXJa-- --f6EVdbUss6DtGAub2xRbTeKVfdheuJikr Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQFLBAEBCAA1FiEELd9y5aWlW6idqkLhwj2R86El/qgFAloTq6QXHHF1d2VucnVv LmJ0cmZzQGdteC5jb20ACgkQwj2R86El/qh/8Af/bRkPKdUYW87ItkCOQmDYznOA YBRbOBrWPyDuODh/l+dcwvf7LwcqjpwaqscaVe3uHLSa8E0zuhQz8710w3T2Fp3o p05hZE2HN+H04vd5b2eF6+gI3DYxGQopY4DfsV8ZXW+sNfO7bFfHDvkSECCD1YAC evugrsGyRWwfTkZnwXkXLCYwP/mpaQk5Nky9lsjMmnphiOzIOJtj3IO0rtJnnvmo MgdNP0yMaZMJBw+XyCX0ZeLafuMK3K9g0/fiJ9rOb3N89DY4OsNN/xxw1pY23tR+ b6YBdBR26N2AkeCybKZfyETmknf4HfDAAIvZ/XlOvEL+AKbHz5GOS4Ohw3P6ZA== =xc5/ -----END PGP SIGNATURE----- --f6EVdbUss6DtGAub2xRbTeKVfdheuJikr--