Hi all,

When I do the following:

cryptsetup open /dev/sdX[Y] rand --type plain --key-file /dev/random;
blkdiscard -z /dev/mapper/rand

Some OOM killings and a kernel panic occur. Here is a screenshot:

Similar issue is NOT found in doing `cat /dev/zero > /dev/mapper/rand`, or 
`blkdiscard -z /dev/sdX[Y]` (without opening a dm-crypt on it), on the same 
hardware and configuration.

Note that `blkdiscard -z` does not trigger the BLKDISCARD ioctl but the 
BLKZEROOUT ioctl. And the devices I have been testing on are USB devices that 
does NOT support WRITE SAME or UNMAP.

Tom Yan

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