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

On Wed, 2 May 2018, John Stoffel wrote:

You miss my point, which is that there's no explanation of what the
difference is between SLAB and SLUB and which I should choose.  The
same goes here.  If the KConfig option doesn't give useful info, it's
useless.

So what, we could write explamantion of that option.

quoted

quoted

Now I also think that Linus has the right idea to not just sprinkle 
BUG_ONs into the code, just dump and oops and keep going if you can.  
If it's a filesystem or a device, turn it read only so that people 
notice right away.

Mikulas> This vmalloc fallback is similar to
Mikulas> CONFIG_DEBUG_KOBJECT_RELEASE.  CONFIG_DEBUG_KOBJECT_RELEASE
Mikulas> changes the behavior of kobject_put in order to cause
Mikulas> deliberate crashes (that wouldn't happen otherwise) in
Mikulas> drivers that misuse kobject_put. In the same sense, we want
Mikulas> to cause deliberate crashes (that wouldn't happen otherwise)
Mikulas> in drivers that misuse kvmalloc.

Mikulas> The crashes will only happen in debugging kernels, not in
Mikulas> production kernels.

Says you.  What about people or distros that enable it
unconditionally?  They're going to get all kinds of reports and then
turn it off again.  Crashing the system isn't the answer here.  

I've made that kvmalloc bug too (in the function 
dm_integrity_free_journal_scatterlist). I'd much rather like if the kernel 
crashed (because then - I would fix the bug). The kernel didn't crash and 
the bug sneaked into the official linux tree, where may be causing random 
crashes for other users.

Mikulas