On 5/31/2021 3:25 PM, Vlastimil Babka wrote:

On 5/31/21 8:55 AM, Faiyaz Mohammed wrote:

quoted

quoted

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.

Hmmm, I think yes we can skip debugfs creation for all cache without
SLAB_STORE_USER	flag set instead of returning error after opening of
file. I will do the change in next patch version.

Thanks and regards,
Mohammed Faiyaz