Hi, While working on improvements w.r.t. open-iscsi userspace package in Debian, I've stumbled upon a weird kernel bug in recent kernel versions that makes the iSCSI initiator unusable.
The test setup is quite simple: LIO target running on the host with fileio backend (I tried both Debian Jessie host with 3.16 kernel and Ubuntu 15.04 host with 3.19 kernel, no difference), initiator running inside a libvirt/KVM instance (Debian sid); nothing special about the setup otherwise. (The target itself shows no problems.) iSCSI login works perfectly fine, reading data from the iSCSI shows no problems otherwise; writing small amounts of data to the iSCSI device also works fine. But writing a bit more at once to the iSCSI device will cause I/O errors in the kernel. Sample messages: [ 21.473911] sd 2:0:0:0: [sda] tag#3 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 21.473914] sd 2:0:0:0: [sda] tag#3 Sense Key : Not Ready [current] [ 21.473916] sd 2:0:0:0: [sda] tag#3 Add. Sense: Logical unit communication failure [ 21.473917] sd 2:0:0:0: [sda] tag#3 CDB: Write(10) 2a 00 00 38 15 d8 00 20 28 00 [ 21.473918] blk_update_request: I/O error, dev sda, sector 3675608 [ 21.473939] EXT4-fs warning (device sda1): ext4_end_bio:329: I/O error -5 writing to inode 46 (offset 50331648 size 4214784 starting block 459707) [ 21.473941] Buffer I/O error on device sda1, logical block 457403 This is obviously a kernel problem, as using Debian Jessie's 3.16 kernel with the same userland will work perfectly fine and not produce any I/O errors, but with more recent kernels this is trivially reproducible for me. I had reported this in the Debian bugtracker against the kernel a while ago, and somebody mentioned that this problem should have been fixed in 4.4, but once I got around to testing 4.4, I can still reproduce that problem. Just now I tried to use the current upstream Linux git branch (basically 4.5-rc1 + the things that Linus already pulled since then as of writing this email) and the problem still persists. The Debian bugreport can be found under: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=805252 Further details, including more log messages, can be found there. I'm not an expert on the block device driver subsystem in the kernel, so I don't really know where to start debugging this, so any help would be appreciated. Thank you. Regards, Christian -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/open-iscsi. For more options, visit https://groups.google.com/d/optout.
