On Wed, Aug 7, 2024 at 12:31 PM Vlastimil Babka <vbabka@xxxxxxx> wrote: > kmem_cache_destroy() includes removing the associated sysfs and debugfs > directories, and the cache from the list of caches that appears in > /proc/slabinfo. Currently this might not happen immediately when: > > - the cache is SLAB_TYPESAFE_BY_RCU and the cleanup is delayed, > including the directores removal > - __kmem_cache_shutdown() fails due to outstanding objects - the > directories remain indefinitely > > When a cache is recreated with the same name, such as due to module > unload followed by a load, the directories will fail to be recreated for > the new instance of the cache due to the old directories being present. > The cache will also appear twice in /proc/slabinfo. > > While we want to convert the SLAB_TYPESAFE_BY_RCU cleanup to be > synchronous again, the second point remains. So let's fix this first and > have the directories and slabinfo removed immediately in > kmem_cache_destroy() and regardless of __kmem_cache_shutdown() success. > > This should not make debugging harder if __kmem_cache_shutdown() fails, > because a detailed report of outstanding objects is printed into dmesg > already due to the failure. Reading this sentence made be curious what __kmem_cache_shutdown() actually does - and I think technically, it prints a report of only the outstanding objects *on the first NUMA node with outstanding objects*? __kmem_cache_shutdown() bails immediately after seeing one node with outstanding objects. That's not really relevant to this series though, just a random observation. > Also simplify kmem_cache_release() sysfs handling by using > __is_defined(SLAB_SUPPORTS_SYSFS). > > Note the resulting code in kmem_cache_destroy() is a bit ugly but will > be further simplified - this is in order to make small bisectable steps. > > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Reviewed-by: Jann Horn <jannh@xxxxxxxxxx>
