XPost: linux.debian.bugs.dist, linux.kernel   
   From: carnil@debian.org   
      
   Hi Jens,   
      
   Kevin Lumik reported in Debian the following issue (not exactly a   
   minimal reproducer, but bisection results follows):   
      
   On Fri, Sep 26, 2025 at 10:34:22AM +0300, Kevin Lumik wrote:   
      
   > Dear Maintainer,   
   >   
   > After upgrading from Debian Bookworm to Trixie, an issue within KVM guests   
   when creating an LVM snapshot of its volume   
   > has surfaced. When a LVM snapshot is taken from the host, the guest starts   
   to get I/O errors. The issue seems to only   
   > appear when aio=io_uring is specified in the KVM drive parameters and also   
   seems to resolve when downgrading the kernel   
   > package down to 6.1. The issue is also not reproducible when using   
   aio=native.   
   >   
   > KVM args for the drive: "-drive id=drive-   
   > virtio0,format=raw,file=/dev/dom/vps_testsql,cache=none,aio=io   
   uring,index=0,media=disk,if=virtio"   
   >   
   > An IO workload is being created in the VM using "fio --randrepeat=1   
   --ioengine=io_uring --direct=1 --gtod_reduce=1 --   
   > name=randwrite --filename=/root/test.bin --bs=4k --iodepth=64 --runtime=60   
   --numjobs=32 --readwrite=randwrite --size=1G   
   > --rwmixread=75 --group_reporting"   
   >   
   > After running "lvcreate -s /dev/dom/vps_testsql -n test -L 1G" on the host   
   we can observe fio erroring out:   
   >   
   > ...   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=46977024, buflen=4096   
   > fio: pid=7367, err=5/file:io_u.c:1876, func=io_u error, error=Input/output   
   error   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=261505024, buflen=4096   
   > fio: pid=7374, err=5/file:io_u.c:1876, func=io_u error, error=Input/output   
   error   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=973840384, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=9637888, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=159965184, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=857505792, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=90787840, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=26427392, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=955621376, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=96169984, buflen=4096   
   > fio: pid=7372, err=5/file:io_u.c:1876, func=io_u error, error=Input/output   
   error   
   > fio: pid=7362, err=5/file:io_u.c:1876, func=io_u error, error=Input/output   
   error   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=203702272, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=814649344, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=91467776, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=948256768, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=105295872, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=75247616, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=1062293504, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=111955968, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=942563328, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=117354496, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=1050402816, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=125419520, buflen=4096   
   > fio: io_u error on file /root/test.bin: Input/output error: write   
   offset=129044480, buflen=4096   
   > fio: pid=7369, err=5/file:io_u.c:1876, func=io_u error, error=Input/output   
   error   
   > fio: pid=7373, err=5/file:io_u.c:1876, func=io_u error, error=Input/output   
   error   
   > fio: pid=7348, err=5/file:io_u.c:1876, func=io_u error, error=Input/output   
   error   
   > fio: pid=7375, err=5/file:io_u.c:1876, func=io_u error, error=Input/output   
   error   
   > fio: pid=7358, err=5/file:io_u.c:1876, func=io_u error, error=Input/output   
   error   
   > fio: pid=7359, err=5/file:io_u.c:1876, func=io_u error, error=Input/output   
   error   
   >   
   > randwrite: (groupid=0, jobs=32): err= 5 (file:io_u.c:1876, func=io_u error,   
   error=Input/output error): pid=7344: Thu Sep   
   > 25 16:28:30 2025   
   >   write: IOPS=194k, BW=758MiB/s (795MB/s)(3976MiB/5244msec); 0 zone resets   
   >    bw (  KiB/s): min=657104, max=1009816, per=100.00%, avg=785345.80,   
   stdev=4331.73, samples=320   
   >    iops        : min=164276, max=252454, avg=196336.40, stdev=1082.93,   
   samples=320   
   >   cpu          : usr=0.33%, sys=1.07%, ctx=18912, majf=0, minf=455   
   >   IO depths    : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=99.8%   
   >      submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%,   
   >=64=0.0%   
   >      complete  : 0=0.1%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.1%,   
   >=64=0.0%   
   >      issued rwts: total=0,1019955,0,0 short=0,0,0,0 dropped=0,0,0,0   
   >      latency   : target=0, window=0, percentile=100.00%, depth=64   
   >   
   > Run status group 0 (all jobs):   
   >   WRITE: bw=758MiB/s (795MB/s), 758MiB/s-758MiB/s (795MB/s-795MB/s),   
   io=3976MiB (4169MB), run=5244-5244msec   
   >   
   > Disk stats (read/write):   
   >   vda: ios=1/1001361, merge=0/2, ticks=0/10314531, in_queue=10314549,   
   util=97.82%   
   > Bus error   
   >   
   > ---   
   >   
   > And the error is also visible in the kernel error log of the VM:   
   > [  361.962970] I/O error, dev vda, sector 83277192 op 0x1:(WRITE) flags   
   0x8800 phys_seg 1 prio class 2   
      
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