I have noticed ext4 filesystem corruption on two of my test alphas with 4.20.0-09062-gd8372ba8ce28.
On AlphaServer DS10:
[10749.664418] EXT4-fs error (device sda2): __ext4_iget:5052: inode #1853093: block 1: comm rsync: invalid block
On AlphaServer DS10L:
[ 5325.064656] EXT4-fs error (device sda2): htree_dirblock_to_tree:1007: inode #1191951: block 4731728: comm rm: bad entry in directory: directory entry overrun - offset=76, inode=417080, rec_len=61816, name_len=35, size=4096
[ 5325.069539] EXT4-fs error (device sda2): htree_dirblock_to_tree:1007: inode #1191951: block 4731728: comm rm: bad entry in directory: directory entry overrun - offset=76, inode=417080, rec_len=61816, name_len=35, size=4096
[ 5325.077351] EXT4-fs error (device sda2): ext4_empty_dir:2718: inode #1191951: block 4731728: comm rm: bad entry in directory: directory entry overrun - offset=76, inode=417080, rec_len=61816, name_len=35, size=4096
Two other alphas, PC-164 and Eiger, worked fine with the same kernel version (different kernel configs according to hardware).
The details:
4.20 worked fine, with gentoo emerge package update after bootup.
Next, 4.20.0-06428-g00c569b567c7 worked fine, with gentoo emerge after bootup.
Next, 4.20.0-09062-gd8372ba8ce28 booted up fine but rsync and rm during start of gentoo emerge errored out like above.
So the corruption _might_ have happened during bootup of previous kernel but it looks more likely that only the latest kernel with blk-mq introduced the problems. mq-deadline is in use on all the alphas.
DS10 has Symbios 53C896 SCSI (sym2 driver), DS10L has QLogic ISP1040, so they are different. Working Eiger and PC164 have sym2 based scsi controllers too.