On Mon, Jul 24, 2023 at 05:43:10PM +0800, Qi Zheng wrote:
> Currently, the shrinker instances can be divided into the following three
> types:
>
> a) global shrinker instance statically defined in the kernel, such as
> workingset_shadow_shrinker.
>
> b) global shrinker instance statically defined in the kernel modules, such
> as mmu_shrinker in x86.
>
> c) shrinker instance embedded in other structures.
>
> For case a, the memory of shrinker instance is never freed. For case b,
> the memory of shrinker instance will be freed after synchronize_rcu() when
> the module is unloaded. For case c, the memory of shrinker instance will
> be freed along with the structure it is embedded in.
>
> In preparation for implementing lockless slab shrink, we need to
> dynamically allocate those shrinker instances in case c, then the memory
> can be dynamically freed alone by calling kfree_rcu().
>
> So this commit adds the following new APIs for dynamically allocating
> shrinker, and add a private_data field to struct shrinker to record and
> get the original embedded structure.
>
> 1. shrinker_alloc()
>
> Used to allocate shrinker instance itself and related memory, it will
> return a pointer to the shrinker instance on success and NULL on failure.
>
> 2. shrinker_free_non_registered()
>
> Used to destroy the non-registered shrinker instance.
This is a bit nasty
>
> 3. shrinker_register()
>
> Used to register the shrinker instance, which is same as the current
> register_shrinker_prepared().
>
> 4. shrinker_unregister()
rename this "shrinker_free()" and key the two different freeing
cases on the SHRINKER_REGISTERED bit rather than mostly duplicating
the two.
void shrinker_free(struct shrinker *shrinker)
{
struct dentry *debugfs_entry = NULL;
int debugfs_id;
if (!shrinker)
return;
down_write(&shrinker_rwsem);
if (shrinker->flags & SHRINKER_REGISTERED) {
list_del(&shrinker->list);
debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id);
} else if (IS_ENABLED(CONFIG_SHRINKER_DEBUG)) {
kfree_const(shrinker->name);
}
if (shrinker->flags & SHRINKER_MEMCG_AWARE)
unregister_memcg_shrinker(shrinker);
up_write(&shrinker_rwsem);
if (debugfs_entry)
shrinker_debugfs_remove(debugfs_entry, debugfs_id);
kfree(shrinker->nr_deferred);
kfree(shrinker);
}
EXPORT_SYMBOL_GPL(shrinker_free);
--
Dave Chinner
david@xxxxxxxxxxxxx
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