Re: [PATCH v2 2/2] loop: Better discard support for block devices

From: Martin K. Petersen
Date: Wed Feb 13 2019 - 21:40:04 EST


> If the backing device for a loop device is a block device, then mirror
> the discard properties of the underlying block device into the loop
> device. While in there, differentiate between REQ_OP_DISCARD and
> REQ_OP_WRITE_ZEROES, which are different for block devices, but which
> the loop device had just been lumping together.

Bubbling up the queue limits from the backing device is fine. However,
I'm not sure why you are requiring a filesystem to be on a
discard-capable device for REQ_OP_DISCARD to have an effect? Punching a
hole in a file is semantically the same as discarding.

Martin K. Petersen Oracle Linux Engineering