CC'ing dm-devel, as this seems to be a dm-related issue. Short summary for new readers: On Linux 5.1 (tested up to 5.1.3), fstrim may discard too many blocks, leading to data loss. I have the following storage stack: btrfs dm-crypt (LUKS) LVM logical volume LVM single physical volume MBR partition Samsung 830 SSD The mapping between logical volumes and physical segments is a bit mixed up. See below for the output for “pvdisplay -m”. When I issue fstrim on the mounted btrfs volume, I get the following kernel messages: attempt to access beyond end of device sda1: rw=16387, want=252755893, limit=250067632 BTRFS warning (device dm-5): failed to trim 1 device(s), last error -5 At the same time, other logical volumes on the same physical volume are destroyed. Also the btrfs volume itself may be damaged (this seems to depend on the actual usage). I can easily reproduce this issue locally and I’m currently bisecting. So far I could narrow down the range of commits to: Good: 92fff53b7191cae566be9ca6752069426c7f8241 Bad: 225557446856448039a9e495da37b72c20071ef2 In this range of commits, there are only dm-related changes. So far, I have not reproduced the issue with other file systems or a simplified stack. I first want to continue bisecting but this may take another day. > Am 18.05.2019 um 12:26 schrieb Qu Wenruo <quwenruo.btrfs@xxxxxxx>: > On 2019/5/18 下午5:18, Michael Laß wrote: >> >>> Am 18.05.2019 um 06:09 schrieb Chris Murphy <lists@xxxxxxxxxxxxxxxxx>: >>> >>> On Fri, May 17, 2019 at 11:37 AM Michael Laß <bevan@xxxxxxxxx> wrote: >>>> >>>> >>>> I tried to reproduce this issue: I recreated the btrfs file system, set up a minimal system and issued fstrim again. It printed the following error message: >>>> >>>> fstrim: /: FITRIM ioctl failed: Input/output error >>> >>> Huh. Any kernel message at the same time? I would expect any fstrim >>> user space error message to also have a kernel message. Any i/o error >>> suggests some kind of storage stack failure - which could be hardware >>> or software, you can't know without seeing the kernel messages. >> >> I missed that. The kernel messages are: >> >> attempt to access beyond end of device >> sda1: rw=16387, want=252755893, limit=250067632 >> BTRFS warning (device dm-5): failed to trim 1 device(s), last error -5 >> >> Here are some more information on the partitions and LVM physical segments: >> >> fdisk -l /dev/sda: >> >> Device Boot Start End Sectors Size Id Type >> /dev/sda1 * 2048 250069679 250067632 119.2G 8e Linux LVM >> >> pvdisplay -m: >> >> --- Physical volume --- >> PV Name /dev/sda1 >> VG Name vg_system >> PV Size 119.24 GiB / not usable <22.34 MiB >> Allocatable yes (but full) >> PE Size 32.00 MiB >> Total PE 3815 >> Free PE 0 >> Allocated PE 3815 >> PV UUID mqCLFy-iDnt-NfdC-lfSv-Maor-V1Ih-RlG8lP >> >> --- Physical Segments --- >> Physical extent 0 to 1248: >> Logical volume /dev/vg_system/btrfs >> Logical extents 2231 to 3479 >> Physical extent 1249 to 1728: >> Logical volume /dev/vg_system/btrfs >> Logical extents 640 to 1119 >> Physical extent 1729 to 1760: >> Logical volume /dev/vg_system/grml-images >> Logical extents 0 to 31 >> Physical extent 1761 to 2016: >> Logical volume /dev/vg_system/swap >> Logical extents 0 to 255 >> Physical extent 2017 to 2047: >> Logical volume /dev/vg_system/btrfs >> Logical extents 3480 to 3510 >> Physical extent 2048 to 2687: >> Logical volume /dev/vg_system/btrfs >> Logical extents 0 to 639 >> Physical extent 2688 to 3007: >> Logical volume /dev/vg_system/btrfs >> Logical extents 1911 to 2230 >> Physical extent 3008 to 3320: >> Logical volume /dev/vg_system/btrfs >> Logical extents 1120 to 1432 >> Physical extent 3321 to 3336: >> Logical volume /dev/vg_system/boot >> Logical extents 0 to 15 >> Physical extent 3337 to 3814: >> Logical volume /dev/vg_system/btrfs >> Logical extents 1433 to 1910 >> >> >> Would btrfs even be able to accidentally trim parts of other LVs or does this clearly hint towards a LVM/dm issue? > > I can't speak sure, but (at least for latest kernel) btrfs has a lot of > extra mount time self check, including chunk stripe check against > underlying device, thus the possibility shouldn't be that high for btrfs. Indeed, bisecting the issue led me to a range of commits that only contains dm-related and no btrfs-related changes. So I assume this is a bug in dm. >> Is there an easy way to somehow trace the trim through the different layers so one can see where it goes wrong? > > Sure, you could use dm-log-writes. > It will record all read/write (including trim) for later replay. > > So in your case, you can build the storage stack like: > > Btrfs > <dm-log-writes> > LUKS/dmcrypt > LVM > MBR partition > Samsung SSD > > Then replay the log (using src/log-write/replay-log in fstests) with > verbose output, you can verify every trim operation against the dmcrypt > device size. > > If all trim are fine, then move the dm-log-writes a layer lower, until > you find which layer is causing the problem. That sounds like a plan! However, I first want to continue bisecting as I am afraid to lose my reproducer by changing parts of my storage stack. Cheers, Michael > > Thanks, > Qu >> >> Cheers, >> Michael >> >> PS: Current state of bisection: It looks like the error was introduced somewhere between b5dd0c658c31b469ccff1b637e5124851e7a4a1c and v5.1. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
