Re: [PATCH] remove BUG() in possible but rare condition

From: Glauber Costa
Date: Wed Apr 11 2012 - 15:04:24 EST


On 04/11/2012 03:57 PM, Linus Torvalds wrote:
On Wed, Apr 11, 2012 at 11:48 AM, Michal Hocko<mhocko@xxxxxxx> wrote:

I am not familiar with the code much but a trivial call chain walk up to
write_dev_supers (in btrfs) shows that we do not check for the return value
from __getblk so we would nullptr and there might be more.
I guess these need some treat before the BUG might be removed, right?

Well, realistically, isn't BUG() as bad as a NULL pointer dereference?

Do you care about the exact message on the screen when your machine dies?
Not particular, but I don't see why (I might be wrong) it would necessarily lead to a NULL pointer dereference.

At least in my test cases, after turning this to a WARN (to make sure it was still being hit), the machine could go on just fine.

I was running this in a container system, with restricted memory. After
killing the container - at least in my ext4 system - everything seemed as happy as ever.

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