On Wed, 2017-11-08 at 09:05 -0600, Christopher Lameter wrote: > On Wed, 8 Nov 2017, Miles Chen wrote: > > > > Ok then the aliasing failed for some reason. The creation of the unique id > > > and the alias detection needs to be in sync otherwise duplicate filenames > > > are created. What is the difference there? > > > > The aliasing failed because find_mergeable() returns if (flags & > > SLAB_NEVER_MERGE) is true. So we do not go to search for alias caches. > > > > __kmem_cache_alias() > > find_mergeable() > > kmem_cache_flags() --> setup flag by the slub_debug > > if (flags & SLAB_NEVER_MERGE) return NULL; > > ... > > search alias logic... > > > > > > The flags maybe changed if disable_higher_order_debug=1. So the > > unmergeable cache becomes mergeable later. > > Ok so make sure taht the aliasing logic also clears those flags before > checking for SLAB_NEVER_MERGE. > > > > The clearing of the DEBUG_METADATA_FLAGS looks ok to me. kmem_cache_alias > > > should do the same right? > > > > > Yes, I think clearing DEBUG_METADATA flags in kmem_cache_alias is > > another solution for this issue. > > > > We will need to do calculate_sizes() by using original flags and compare > > the order of s->size and s->object_size when > > disable_higher_order_debug=1. > > Hmmm... Or move the aliasing check to a point where we know the size of > the slab objects? The biggest concern is that we may have some merged caches even if we enable CONFIG_SLUB_DEBUG_ON and slub_debug=O. So a developer cannot say "I set CONFIG_SLUB_DEBUG_ON=y to stop all slab merging". (https://www.spinics.net/lists/linux-mm/msg77919.html) In this fix patch, it disables slab merging if SLUB_DEBUG=O and CONFIG_SLUB_DEBUG_ON=y but the debug features are disabled by the disable_higher_order_debug logic and it holds the "slab merging is off if any debug features are enabled" behavior. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
