kernel.git/mm/slub.c, branch linux-3.8.y

slub: drop mutex before deleting sysfs entry

2012-12-18T23:02:15Z

Sasha Levin recently reported a lockdep problem resulting from the new attribute propagation introduced by kmemcg series. In short, slab_mutex will be called from within the sysfs attribute store function. This will create a dependency, that will later be held backwards when a cache is destroyed - since destruction occurs with the slab_mutex held, and then calls in to the sysfs directory removal function. In this patch, I propose to adopt a strategy close to what __kmem_cache_create does before calling sysfs_slab_add, and release the lock before the call to sysfs_slab_remove. This is pretty much the last operation in the kmem_cache_shutdown() path, so we could do better by splitting this and moving this call alone to later on. This will fit nicely when sysfs handling is consistent between all caches, but will look weird now. Lockdep info: ====================================================== [ INFO: possible circular locking dependency detected ] 3.7.0-rc4-next-20121106-sasha-00008-g353b62f #117 Tainted: G W ------------------------------------------------------- trinity-child13/6961 is trying to acquire lock: (s_active#43){++++.+}, at: sysfs_addrm_finish+0x31/0x60 but task is already holding lock: (slab_mutex){+.+.+.}, at: kmem_cache_destroy+0x22/0xe0 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (slab_mutex){+.+.+.}: lock_acquire+0x1aa/0x240 __mutex_lock_common+0x59/0x5a0 mutex_lock_nested+0x3f/0x50 slab_attr_store+0xde/0x110 sysfs_write_file+0xfa/0x150 vfs_write+0xb0/0x180 sys_pwrite64+0x60/0xb0 tracesys+0xe1/0xe6 -> #0 (s_active#43){++++.+}: __lock_acquire+0x14df/0x1ca0 lock_acquire+0x1aa/0x240 sysfs_deactivate+0x122/0x1a0 sysfs_addrm_finish+0x31/0x60 sysfs_remove_dir+0x89/0xd0 kobject_del+0x16/0x40 __kmem_cache_shutdown+0x40/0x60 kmem_cache_destroy+0x40/0xe0 mon_text_release+0x78/0xe0 __fput+0x122/0x2d0 ____fput+0x9/0x10 task_work_run+0xbe/0x100 do_exit+0x432/0xbd0 do_group_exit+0x84/0xd0 get_signal_to_deliver+0x81d/0x930 do_signal+0x3a/0x950 do_notify_resume+0x3e/0x90 int_signal+0x12/0x17 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(slab_mutex); lock(s_active#43); lock(slab_mutex); lock(s_active#43); *** DEADLOCK *** 2 locks held by trinity-child13/6961: #0: (mon_lock){+.+.+.}, at: mon_text_release+0x25/0xe0 #1: (slab_mutex){+.+.+.}, at: kmem_cache_destroy+0x22/0xe0 stack backtrace: Pid: 6961, comm: trinity-child13 Tainted: G W 3.7.0-rc4-next-20121106-sasha-00008-g353b62f #117 Call Trace: print_circular_bug+0x1fb/0x20c __lock_acquire+0x14df/0x1ca0 lock_acquire+0x1aa/0x240 sysfs_deactivate+0x122/0x1a0 sysfs_addrm_finish+0x31/0x60 sysfs_remove_dir+0x89/0xd0 kobject_del+0x16/0x40 __kmem_cache_shutdown+0x40/0x60 kmem_cache_destroy+0x40/0xe0 mon_text_release+0x78/0xe0 __fput+0x122/0x2d0 ____fput+0x9/0x10 task_work_run+0xbe/0x100 do_exit+0x432/0xbd0 do_group_exit+0x84/0xd0 get_signal_to_deliver+0x81d/0x930 do_signal+0x3a/0x950 do_notify_resume+0x3e/0x90 int_signal+0x12/0x17 Signed-off-by: Glauber Costa Reported-by: Sasha Levin Cc: Michal Hocko Cc: Kamezawa Hiroyuki Cc: Johannes Weiner Cc: Christoph Lameter Cc: Pekka Enberg Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memcg: add comments clarifying aspects of cache attribute propagation

2012-12-18T23:02:15Z

This patch clarifies two aspects of cache attribute propagation. First, the expected context for the for_each_memcg_cache macro in memcontrol.h. The usages already in the codebase are safe. In mm/slub.c, it is trivially safe because the lock is acquired right before the loop. In mm/slab.c, it is less so: the lock is acquired by an outer function a few steps back in the stack, so a VM_BUG_ON() is added to make sure it is indeed safe. A comment is also added to detail why we are returning the value of the parent cache and ignoring the children's when we propagate the attributes. Signed-off-by: Glauber Costa Cc: Michal Hocko Cc: Kamezawa Hiroyuki Cc: Johannes Weiner Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

slub: slub-specific propagation changes

2012-12-18T23:02:14Z

SLUB allows us to tune a particular cache behavior with sysfs-based tunables. When creating a new memcg cache copy, we'd like to preserve any tunables the parent cache already had. This can be done by tapping into the store attribute function provided by the allocator. We of course don't need to mess with read-only fields. Since the attributes can have multiple types and are stored internally by sysfs, the best strategy is to issue a ->show() in the root cache, and then ->store() in the memcg cache. The drawback of that, is that sysfs can allocate up to a page in buffering for show(), that we are likely not to need, but also can't guarantee. To avoid always allocating a page for that, we can update the caches at store time with the maximum attribute size ever stored to the root cache. We will then get a buffer big enough to hold it. The corolary to this, is that if no stores happened, nothing will be propagated. It can also happen that a root cache has its tunables updated during normal system operation. In this case, we will propagate the change to all caches that are already active. [akpm@linux-foundation.org: tweak code to avoid __maybe_unused] Signed-off-by: Glauber Costa Cc: Christoph Lameter Cc: David Rientjes Cc: Frederic Weisbecker Cc: Greg Thelen Cc: Johannes Weiner Cc: JoonSoo Kim Cc: KAMEZAWA Hiroyuki Cc: Mel Gorman Cc: Michal Hocko Cc: Pekka Enberg Cc: Rik van Riel Cc: Suleiman Souhlal Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memcg: destroy memcg caches

2012-12-18T23:02:14Z

Implement destruction of memcg caches. Right now, only caches where our reference counter is the last remaining are deleted. If there are any other reference counters around, we just leave the caches lying around until they go away. When that happens, a destruction function is called from the cache code. Caches are only destroyed in process context, so we queue them up for later processing in the general case. Signed-off-by: Glauber Costa Cc: Christoph Lameter Cc: David Rientjes Cc: Frederic Weisbecker Cc: Greg Thelen Cc: Johannes Weiner Cc: JoonSoo Kim Cc: KAMEZAWA Hiroyuki Cc: Mel Gorman Cc: Michal Hocko Cc: Pekka Enberg Cc: Rik van Riel Cc: Suleiman Souhlal Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sl[au]b: allocate objects from memcg cache

2012-12-18T23:02:14Z

We are able to match a cache allocation to a particular memcg. If the task doesn't change groups during the allocation itself - a rare event, this will give us a good picture about who is the first group to touch a cache page. This patch uses the now available infrastructure by calling memcg_kmem_get_cache() before all the cache allocations. Signed-off-by: Glauber Costa Cc: Christoph Lameter Cc: David Rientjes Cc: Frederic Weisbecker Cc: Greg Thelen Cc: Johannes Weiner Cc: JoonSoo Kim Cc: KAMEZAWA Hiroyuki Cc: Mel Gorman Cc: Michal Hocko Cc: Pekka Enberg Cc: Rik van Riel Cc: Suleiman Souhlal Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sl[au]b: always get the cache from its page in kmem_cache_free()

2012-12-18T23:02:14Z

struct page already has this information. If we start chaining caches, this information will always be more trustworthy than whatever is passed into the function. Signed-off-by: Glauber Costa Cc: Christoph Lameter Cc: David Rientjes Cc: Frederic Weisbecker Cc: Greg Thelen Cc: Johannes Weiner Cc: JoonSoo Kim Cc: KAMEZAWA Hiroyuki Cc: Mel Gorman Cc: Michal Hocko Cc: Pekka Enberg Cc: Rik van Riel Cc: Suleiman Souhlal Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

slab/slub: consider a memcg parameter in kmem_create_cache

2012-12-18T23:02:13Z

Allow a memcg parameter to be passed during cache creation. When the slub allocator is being used, it will only merge caches that belong to the same memcg. We'll do this by scanning the global list, and then translating the cache to a memcg-specific cache Default function is created as a wrapper, passing NULL to the memcg version. We only merge caches that belong to the same memcg. A helper is provided, memcg_css_id: because slub needs a unique cache name for sysfs. Since this is visible, but not the canonical location for slab data, the cache name is not used, the css_id should suffice. Signed-off-by: Glauber Costa Cc: Christoph Lameter Cc: David Rientjes Cc: Frederic Weisbecker Cc: Greg Thelen Cc: Johannes Weiner Cc: JoonSoo Kim Cc: KAMEZAWA Hiroyuki Cc: Mel Gorman Cc: Michal Hocko Cc: Pekka Enberg Cc: Rik van Riel Cc: Suleiman Souhlal Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'slab/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux

2012-12-18T18:56:07Z

Pull SLAB changes from Pekka Enberg: "This contains preparational work from Christoph Lameter and Glauber Costa for SLAB memcg and cleanups and improvements from Ezequiel Garcia and Joonsoo Kim. Please note that the SLOB cleanup commit from Arnd Bergmann already appears in your tree but I had also merged it myself which is why it shows up in the shortlog." * 'slab/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux: mm/sl[aou]b: Common alignment code slab: Use the new create_boot_cache function to simplify bootstrap slub: Use statically allocated kmem_cache boot structure for bootstrap mm, sl[au]b: create common functions for boot slab creation slab: Simplify bootstrap slub: Use correct cpu_slab on dead cpu mm: fix slab.c kernel-doc warnings mm/slob: use min_t() to compare ARCH_SLAB_MINALIGN slab: Ignore internal flags in cache creation mm/slob: Use free_page instead of put_page for page-size kmalloc allocations mm/sl[aou]b: Move common kmem_cache_size() to slab.h mm/slob: Use object_size field in kmem_cache_size() mm/slob: Drop usage of page->private for storing page-sized allocations slub: Commonize slab_cache field in struct page sl[au]b: Process slabinfo_show in common code mm/sl[au]b: Move print_slabinfo_header to slab_common.c mm/sl[au]b: Move slabinfo processing to slab_common.c slub: remove one code path and reduce lock contention in __slab_free()

slub, hotplug: ignore unrelated node's hot-adding and hot-removing

2012-12-12T01:22:23Z

SLUB only focuses on the nodes which have normal memory and it ignores the other node's hot-adding and hot-removing. Aka: if some memory of a node which has no onlined memory is online, but this new memory onlined is not normal memory (for example, highmem), we should not allocate kmem_cache_node for SLUB. And if the last normal memory is offlined, but the node still has memory, we should remove kmem_cache_node for that node. (The current code delays it when all of the memory is offlined) So we only do something when marg->status_change_nid_normal > 0. marg->status_change_nid is not suitable here. The same problem doesn't exist in SLAB, because SLAB allocates kmem_list3 for every node even the node don't have normal memory, SLAB tolerates kmem_list3 on alien nodes. SLUB only focuses on the nodes which have normal memory, it don't tolerate alien kmem_cache_node. The patch makes SLUB become self-compatible and avoids WARNs and BUGs in rare conditions. Signed-off-by: Lai Jiangshan Cc: David Rientjes Cc: Minchan Kim Cc: KOSAKI Motohiro Cc: Yasuaki Ishimatsu Cc: Rob Landley Cc: Andrew Morton Cc: Jiang Liu Cc: Kay Sievers Cc: Greg Kroah-Hartman Cc: Mel Gorman Cc: Wen Congyang Acked-by: Christoph Lameter Cc: Pekka Enberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/sl[aou]b: Common alignment code

2012-12-11T10:14:28Z

Extract the code to do object alignment from the allocators. Do the alignment calculations in slab_common so that the __kmem_cache_create functions of the allocators do not have to deal with alignment. Signed-off-by: Christoph Lameter Signed-off-by: Pekka Enberg