module: add a sanity check prior to allowing kernel module auto-loading
request_module() is what we use for kernel-module autoloading. But
this today is pretty stupid, it just requests for the module without
even checking if its needed. And so we bounce to userspace and hope
for the best.
We can instead do a simple check to see if the module is already
present. This will however contend the module_mutex, but it should
never be heavily contended. However, module auto-loading is a special
use case in the kernel and kernel/kmod already limits the amount of
concurrent requests from the kernel to 50 so we know the kernel can
only contend on the module_mutex for querying if a module exists 50
times at any single point in time.
This work is only valuable if it proves useful for booting up large
systems where a lot of current kernel heuristics use many kernel
module auto-loading features and they could benefit from this. There
are no metrics yet to show, but at least this doesn't penalize much
existing systems.
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
3 files changed
