Re: [PATCH] conditionalize some boring buffer_head checks

[Andrew Morton]

Jeff Garzik <jgarzik@xxxxxxxxx> wrote:
>
> 
> These checks are executed billions of times per day, with no stack dump 
> bug reports sent to lkml.  Arguably, they will only trigger on buggy 
> filesystems (programmer error), and thus IMO shouldn't even be executed 
> in a non-debug kernel.
> 
> Even though BUG_ON() includes unlikely(), I think this patch -- or 
> something like it -- is preferable.  The buffer_error() checks aren't 
> even marked unlikely().
> 
> This is a micro-optimization on a key kernel fast path.
> 

buffer_error() was always supposed to be temporary.  Once per month someone
reports the one in __find_get_block_slow(), but that's all.  The only
reason for keeping it around is as a debug aid to filesystem developers.

We could make it a no-op if !CONFIG_BUFFER_DEBUG.
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