Am Sun, 21 Jun 2015 07:21:03 +0000 schrieb Paul Jones <p...@pauljones.id.au>:
> > -----Original Message----- > > From: Lutz Euler [mailto:lutz.eu...@freenet.de] > > Sent: Sunday, 21 June 2015 12:11 AM > > To: Christian; Paul Jones; Austin S Hemmelgarn > > Cc: linux-btrfs@vger.kernel.org > > Subject: RE: trim not working and irreparable errors from btrfsck > > > > Hi Christian, Paul and Austin, > > > > Christian wrote: > > > However, fstrim still gives me "0 B (0 bytes) trimmed, so that may be > > > another problem. Is there a way to check if trim works? > > > > Paul wrote: > > > I've got the same problem. I've got 2 SSDs with 2 partitions in RAID1, > > > fstrim always works on the 2nd partition but not the first. There are > > > no errors on either filesystem that I know of, but the first one is > > > root so I can't take it offline to run btrfs check. > > > > Austin wrote: > > > I'm seeing the same issue here, but with a Crucial brand SSD. > > > Somewhat interestingly, I don't see any issues like this with BTRFS on > > > top of LVM's thin-provisioning volumes, or with any other filesystems, > > > so I think it has something to do with how BTRFS is reporting unused > > > space or how it is submitting the discard requests. > > > > Probably you all suffer from the same problem I had a few years ago. > > It is a bug in how btrfs implements fstrim. > > > > To check whether you are a victim of this bug simply run: > > > > # btrfs-debug-tree /dev/whatever | grep 'FIRST_CHUNK_TREE > > CHUNK_ITEM' > > > > where /dev/whatever is a device of your filesystem, and interrupt after the > > first several output lines with C-c. (Officially the filesystem should be > > unmounted when running btrfs-debug-tree, but that is not necessary as we > > only read from it and the relevant data doesn't change very often.) > > > > You get something like: > > > > item 2 key (FIRST_CHUNK_TREE CHUNK_ITEM 0) > > item 3 key (FIRST_CHUNK_TREE CHUNK_ITEM 12947816448) > > item 4 key (FIRST_CHUNK_TREE CHUNK_ITEM 14021558272) > > ... > > > > (This output is from an old version of btrfs-progs. I understand newer > > version > > are more verbose, but you should nevertheless easily be able to interpret > > the output). > > > > If the first number different from 0 (here, the 12947816448) is larger than > > the > > sum of the sizes of the devices the filesystem consists of, bingo. > > > > This has been discussed already in the past and there is a patch. > > > > Please see for the patch: > > http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg40618.html > > > > and for the background: > > http://comments.gmane.org/gmane.comp.file-systems.btrfs/15597 > > > > Kind regards, > > > > Lutz Euler > > I tried the test and the numbers I was getting seemed reasonable, however I > went ahead and applied the patch anyway. Trim now works correctly! > > Thanks, > Paul. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in Speaking as a user, since "fstrim -av" still always outputs 0 bytes trimmed on my system: what's the status of this? Did anybody ever file a bug report? There was also that other thread, "fstrim not working on one of three BTRFS filesystems", that also never went anywhere. I take it from this that my SSD has been running untrimmed for quite a while now? (FWIW, queued trim is blocked by my kernel (it's "forced_unqueued"), but fstrim should still start an unqueued trim, right?) # uname -a Linux thetick 4.1.4-gentoo #1 SMP PREEMPT Tue Aug 4 21:58:41 CEST 2015 x86_64 AMD Athlon(tm) 64 X2 Dual Core Processor 4200+ AuthenticAMD GNU/Linux # btrfs --version btrfs-progs v4.1.2 # btrfs filesystem show Label: 'MARCEC_ROOT' uuid: 0267d8b3-a074-460a-832d-5d5fd36bae64 Total devices 1 FS bytes used 56.59GiB devid 1 size 107.79GiB used 69.03GiB path /dev/sda1 Label: 'MARCEC_STORAGE' uuid: 472c9290-3ff2-4096-9c47-0612d3a52cef Total devices 2 FS bytes used 597.75GiB devid 1 size 931.51GiB used 600.03GiB path /dev/sdc devid 2 size 931.51GiB used 600.03GiB path /dev/sdb Label: 'MARCEC_BACKUP' uuid: f97b3cda-15e8-418b-bb9b-235391ef2a38 Total devices 1 FS bytes used 807.59GiB devid 1 size 976.56GiB used 837.06GiB path /dev/sdd2 btrfs-progs v4.1.2 # btrfs filesystem df / Data, single: total=65.00GiB, used=54.83GiB System, single: total=32.00MiB, used=16.00KiB Metadata, single: total=4.00GiB, used=1.76GiB GlobalReserve, single: total=512.00MiB, used=0.00B Greetings -- Marc Joliet -- "People who think they know everything really annoy those of us who know we don't" - Bjarne Stroustrup
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