Running Slackware64-current on an IBM x3650 server, after upgrading system to kernel version 4.19.5, I am no longer able to write data to my LTO tape drives. Using a Dell PowerVault 132t connected to the server via an Adaptec ASC-29320ALP U320 card (aic79xx module).  I can run the mtx command to load/unload and move tapes around fine, and the mt command also works fine with accessing tapes in either of the LTO2 drives.  However, if I run the command "tar -cvf /dev/st0 /path/to/backup", the system acts like it is writing the files to tape, but nothing seems to get actually written except filemarks.  Running a "tar -tvf /dev/st0" immediately exits.  Reverting back to the Slackware64-current kernel-generic-4.19.4 package and everything works fine again.  This same thing is happening on a second Slackware64-current IBM workstation, with an Adaptec AHA-2940U2/U2W card (aic7xxx module), accessing a second PowerVault 132t tape library. There are no logs generated in /var/log/syslog or /var/log/messages on either system.  Latest kernel tested is 4.19.8.  If I write data to tape with 4.19.4, I am still able to read it with the newer kernels, but data written with 4.19.5 or higher cannot be read.