On 5/31/21 8:55 AM, Faiyaz Mohammed wrote: >> I don't see any of the symlinks under /sys/kernel/debug/slab/, so I think the >> aliases handling code is wrong, and I can see at least two reasons why it could be: >> > > I think I missed one thing, when CONFIG_SLUB_DEBUG_ON enable or > slub_debug is pass through command line __kmem_cache_alias() will return > null, so no symlinks will be created even if CONFIG_SLAB_MERGE_DEFAULT > is enable and to store user data we need to enable CONFIG_SLUB_DEBUG_ON > or pass slub_debug through command line. So you're saying that caches with SLAB_STORE_USER can never be aliases as the merging logic will prevent merging with any debug flag, including STORE_USER. So if we ignore aliases, it means we will not create the debugfs files for caches, where opening the files would just return error, so we don't lose anything by not creating the files in the first place. In that case, for consistency I would recommend to skip debugfs creation for all caches without SLAB_STORE_USER (even if the caches are not an alias). I think we can make this decision now as it's a whole new debugfs subtree so we don't break any pre-existing code.
