Re: [dm-devel] [PATCH v5] fault-injection: introduce kvmalloc fallback options

[Mikulas Patocka]

On Thu, 26 Apr 2018, Michael S. Tsirkin wrote:

> On Thu, Apr 26, 2018 at 12:07:25PM -0400, Mikulas Patocka wrote:
> > > IIUC debug kernels mainly exist so people who experience e.g. memory
> > > corruption can try and debug the failure. In this case, CONFIG_DEBUG_SG
> > > will *already* catch a failure early. Nothing special needs to be done.
> > 
> > The patch helps people debug such memory coprruptions (such as using DMA 
> > API on the result of kvmalloc).
> 
> That's my point.  I don't think your patch helps debug any memory
> corruptions.  With CONFIG_DEBUG_SG using DMA API already causes a
> BUG_ON, that's before any memory can get corrupted.

The patch turns a hard-to-reproduce bug into an easy-to-reproduce bug. 

Obviously we don't want this in production kernels, but in the debug 
kernels it should be done.

Mikulas