Hi :) I'm on Deepin 20 beta, which is based on Debian. Linux deepin 5.3.0-3-amd64 #1 SMP deepin 5.3.15-6apricot (2020-04-13) x86_64 GNU/Linux btrfs-progs v4.20.1 Label: none uuid: 01775a38-62bb-4bf2-b6a0-d5af252b3435 Total devices 1 FS bytes used 883.55MiB devid 1 size 1000.00MiB used 999.00MiB path /dev/loop0 Data, single: total=883.00MiB, used=882.44MiB System, DUP: total=8.00MiB, used=16.00KiB Metadata, DUP: total=50.00MiB, used=1.09MiB GlobalReserve, single: total=16.00MiB, used=0.00B I was testing btrfs to see data checksumming behavior when encountering a rotten area, so I set up a loop device backed by a 1GB file. I filled it with a compressed file and made it rot with, e.g., dd if=/dev/zero of=loopie bs=1k seek=800000 count=1 That is, the equivalent of having data on a single block on an actual hard drive go bad. I did this different places in the loopback file, with the same result: Reading the file back from btrfs seems possible before the point at which the bad block of data is encoutered, and then *most* reads from beyond that point yield IO errors. E.g.: daniel@deepin ~ sudo dd of=/dev/null if=/mnt/file bs=1M count=100 status=progress conv=sync,noerror 100+0 records in 100+0 records out 104857600 bytes (105 MB, 100 MiB) copied, 0.0150797 s, 7.0 GB/s daniel@deepin ~ sudo dd of=/dev/null if=/mnt/file bs=1M count=100 skip=700 status=progress conv=sync,noerror dd: error reading '/mnt/file': Input/output error 34+0 records in 34+0 records out ... snip 39 more errors ... daniel@deepin ~ sudo dd of=/dev/null if=/mnt/file bs=1M count=100 skip=600 status=progress conv=sync,noerror dd: error reading '/mnt/file': Input/output error 66+1 records in 67+0 records out ... snip 36 more errors ... daniel@deepin ~ sudo dd of=/dev/null if=/mnt/file bs=1M count=100 skip=300 status=progress conv=sync,noerror dd: error reading '/mnt/file': Input/output error 26+0 records in 26+0 records out ... snip 63 more errors ... This seems ... well, wrong. Like, in, bug wrong. Surely, a single block of bad data on a device shouldn't cause btrfs to produce such a cascade of errors, making so much data inaccessible? Cheers :) Daniel
