Dennis Zhou (Facebook) 59b57717ff blkcg: delay blkg destruction until after writeback has finished ... Currently, blkcg destruction relies on a sequence of events: 1. Destruction starts. blkcg_css_offline() is called and blkgs release their reference to the blkcg. This immediately destroys the cgwbs (writeback). 2. With blkgs giving up their reference, the blkcg ref count should become zero and eventually call blkcg_css_free() which finally frees the blkcg. Jiufei Xue reported that there is a race between blkcg_bio_issue_check() and cgroup_rmdir(). To remedy this, blkg destruction becomes contingent on the completion of all writeback associated with the blkcg. A count of the number of cgwbs is maintained and once that goes to zero, blkg destruction can follow. This should prevent premature blkg destruction related to writeback. The new process for blkcg cleanup is as follows: 1. Destruction starts. blkcg_css_offline() is called which offlines writeback. Blkg destruction is delayed on the cgwb_refcnt count to avoid punting potentially large amounts of outstanding writeback to root while maintaining any ongoing policies. Here, the base cgwb_refcnt is put back. 2. When the cgwb_refcnt becomes zero, blkcg_destroy_blkgs() is called and handles destruction of blkgs. This is where the css reference held by each blkg is released. 3. Once the blkcg ref count goes to zero, blkcg_css_free() is called. This finally frees the blkg. It seems in the past blk-throttle didn't do the most understandable things with taking data from a blkg while associating with current. So, the simplification and unification of what blk-throttle is doing caused this. Fixes: 08e18eab0c ("block: add bi_blkg to the bio for cgroups") Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Dennis Zhou <dennisszhou@gmail.com> Cc: Jiufei Xue <jiufei.xue@linux.alibaba.com> Cc: Joseph Qi <joseph.qi@linux.alibaba.com> Cc: Tejun Heo <tj@kernel.org> Cc: Josef Bacik <josef@toxicpanda.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Jens Axboe <axboe@kernel.dk>		2018-08-31 14:48:56 -06:00
..
kasan	kernel/memremap, kasan: make ZONE_DEVICE with work with KASAN	2018-08-17 16:20:30 -07:00
Kconfig	mm, swap: make CONFIG_THP_SWAP depend on CONFIG_SWAP	2018-08-17 16:20:32 -07:00
Kconfig.debug	mm: clarify CONFIG_PAGE_POISONING and usage	2018-08-22 10:52:44 -07:00
Makefile	mm: restructure memfd code	2018-06-07 17:34:35 -07:00
backing-dev.c	blkcg: delay blkg destruction until after writeback has finished	2018-08-31 14:48:56 -06:00
balloon_compaction.c	…
bootmem.c	docs/mm: bootmem: add overview documentation	2018-08-02 12:17:27 -06:00
cleancache.c	mm: use octal not symbolic permissions	2018-06-15 07:55:25 +09:00
cma.c	mm/cma: remove unsupported gfp_mask parameter from cma_alloc()	2018-08-17 16:20:32 -07:00
cma.h	…
cma_debug.c	mm/cma: remove unsupported gfp_mask parameter from cma_alloc()	2018-08-17 16:20:32 -07:00
compaction.c	mm: use octal not symbolic permissions	2018-06-15 07:55:25 +09:00
debug.c	mm: teach dump_page() to correctly output poisoned struct pages	2018-07-03 17:32:19 -07:00
debug_page_ref.c	…
dmapool.c	mm: use octal not symbolic permissions	2018-06-15 07:55:25 +09:00
early_ioremap.c	…
fadvise.c	mm/fadvise.c: fix signed overflow UBSAN complaint	2018-08-17 16:20:30 -07:00
failslab.c	mm: use octal not symbolic permissions	2018-06-15 07:55:25 +09:00
filemap.c	mm: use new return type vm_fault_t	2018-06-07 17:34:36 -07:00
frame_vector.c	…
frontswap.c	mm: use octal not symbolic permissions	2018-06-15 07:55:25 +09:00
gup.c	mm: Change return type int to vm_fault_t for fault handlers	2018-08-23 18:48:44 -07:00
gup_benchmark.c	treewide: kvzalloc() -> kvcalloc()	2018-06-12 16:19:22 -07:00
highmem.c	…
hmm.c	mm, oom: distinguish blockable mode for mmu notifiers	2018-08-22 10:52:44 -07:00
huge_memory.c	mm: Change return type int to vm_fault_t for fault handlers	2018-08-23 18:48:44 -07:00
hugetlb.c	mm: Change return type int to vm_fault_t for fault handlers	2018-08-23 18:48:44 -07:00
hugetlb_cgroup.c	mm: rename page_counter's count/limit into usage/max	2018-06-07 17:34:35 -07:00
hwpoison-inject.c	…
init-mm.c	mm: Allocate the mm_cpumask (mm->cpu_bitmap[]) dynamically based on nr_cpu_ids	2018-07-17 09:35:30 +02:00
internal.h	mm: Change return type int to vm_fault_t for fault handlers	2018-08-23 18:48:44 -07:00
interval_tree.c	…
khugepaged.c	mm: Change return type int to vm_fault_t for fault handlers	2018-08-23 18:48:44 -07:00
kmemleak-test.c	…
kmemleak.c	mm: kernel-doc: add missing parameter descriptions	2018-04-05 21:36:27 -07:00
ksm.c	include/linux/compiler*.h: make compiler-*.h mutually exclusive	2018-08-22 17:31:34 -07:00
list_lru.c	mm/list_lru: introduce list_lru_shrink_walk_irq()	2018-08-17 16:20:32 -07:00
maccess.c	…
madvise.c	…
memblock.c	mm/memblock.c: replace u64 with phys_addr_t where appropriate	2018-08-17 16:20:30 -07:00
memcontrol.c	mm, oom: introduce memory.oom.group	2018-08-22 10:52:45 -07:00
memfd.c	alloc_file(): switch to passing O_... flags instead of FMODE_... mode	2018-07-12 10:02:57 -04:00
memory-failure.c	mm: soft-offline: close the race against page allocation	2018-08-23 18:48:43 -07:00
memory.c	mm/cow: don't bother write protecting already write-protected pages	2018-08-25 13:15:03 -07:00
memory_hotplug.c	mm/page_alloc: Introduce free_area_init_core_hotplug	2018-08-22 10:52:45 -07:00
mempolicy.c	mm: access zone->node via zone_to_nid() and zone_set_nid()	2018-08-22 10:52:45 -07:00
mempool.c	mm/mempool.c: add missing parameter description	2018-08-22 10:52:44 -07:00
memtest.c	…
migrate.c	mm: soft-offline: close the race against page allocation	2018-08-23 18:48:43 -07:00
mincore.c	…
mlock.c	dax: remove VM_MIXEDMAP for fsdax and device dax	2018-08-17 16:20:27 -07:00
mm_init.c	mm: access zone->node via zone_to_nid() and zone_set_nid()	2018-08-22 10:52:45 -07:00
mmap.c	mm, oom: remove oom_lock from oom_reaper	2018-08-22 10:52:44 -07:00
mmu_context.c	…
mmu_notifier.c	mm, oom: distinguish blockable mode for mmu notifiers	2018-08-22 10:52:44 -07:00
mmzone.c	…
mprotect.c	x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings	2018-06-20 19:10:01 +02:00
mremap.c	mremap: remove LATENCY_LIMIT from mremap to reduce the number of TLB shootdowns	2018-06-15 07:55:24 +09:00
msync.c	…
nobootmem.c	mm/memblock: add a name for memblock flags enumeration	2018-08-02 12:17:27 -06:00
nommu.c	mm: provide a fallback for PAGE_KERNEL_EXEC for architectures	2018-08-17 16:20:29 -07:00
oom_kill.c	Merge branch 'akpm' (patches from Andrew)	2018-08-22 12:34:08 -07:00
page-writeback.c	mm/page-writeback.c: update stale account_page_redirty() comment	2018-08-17 16:20:30 -07:00
page_alloc.c	mm: soft-offline: close the race against page allocation	2018-08-23 18:48:43 -07:00
page_counter.c	memcg: introduce memory.min	2018-06-07 17:34:36 -07:00
page_ext.c	mm/page_ext.c: constify lookup_page_ext() argument	2018-08-17 16:20:28 -07:00
page_idle.c	mm: use octal not symbolic permissions	2018-06-15 07:55:25 +09:00
page_io.c	swap,blkcg: issue swap io with the appropriate context	2018-07-09 09:07:54 -06:00
page_isolation.c	mm, migrate: remove reason argument from new_page_t	2018-04-11 10:28:32 -07:00
page_owner.c	mm: use octal not symbolic permissions	2018-06-15 07:55:25 +09:00
page_poison.c	mm/page_poison.c: make early_page_poison_param() __init	2018-04-05 21:36:26 -07:00
page_vma_mapped.c	…
pagewalk.c	mm: kernel-doc: add missing parameter descriptions	2018-04-05 21:36:27 -07:00
percpu-internal.h	…
percpu-km.c	…
percpu-stats.c	treewide: Use array_size() in vmalloc()	2018-06-12 16:19:22 -07:00
percpu-vm.c	…
percpu.c	/proc/meminfo: add percpu populated pages count	2018-08-22 10:52:45 -07:00
pgtable-generic.c	…
process_vm_access.c	…
quicklist.c	…
readahead.c	readahead: stricter check for bdi io_pages	2018-07-27 09:09:53 -06:00
rmap.c	mm: do not drop unused pages when userfaultd is running	2018-07-14 11:11:09 -07:00
rodata_test.c	…
shmem.c	mm: Change return type int to vm_fault_t for fault handlers	2018-08-23 18:48:44 -07:00
slab.c	treewide: kzalloc() -> kcalloc()	2018-06-12 16:19:22 -07:00
slab.h	mm: introduce CONFIG_MEMCG_KMEM as combination of CONFIG_MEMCG && !CONFIG_SLOB	2018-08-17 16:20:30 -07:00
slab_common.c	mm: introduce CONFIG_MEMCG_KMEM as combination of CONFIG_MEMCG && !CONFIG_SLOB	2018-08-17 16:20:30 -07:00
slob.c	slab: __GFP_ZERO is incompatible with a constructor	2018-06-07 17:34:34 -07:00
slub.c	mm, slub: restore the original intention of prefetch_freepointer()	2018-08-17 16:20:28 -07:00
sparse-vmemmap.c	mm/sparse: delete old sparse_init and enable new one	2018-08-17 16:20:32 -07:00
sparse.c	mm/sparse: delete old sparse_init and enable new one	2018-08-17 16:20:32 -07:00
swap.c	mm: introduce MEMORY_DEVICE_FS_DAX and CONFIG_DEV_PAGEMAP_OPS	2018-05-22 06:59:39 -07:00
swap_cgroup.c	…
swap_slots.c	mm, swap, get_swap_pages: use entry_size instead of cluster in parameter	2018-08-22 10:52:44 -07:00
swap_state.c	treewide: kvzalloc() -> kvcalloc()	2018-06-12 16:19:22 -07:00
swapfile.c	mm/swapfile.c: put_swap_page: share more between huge/normal code path	2018-08-22 10:52:44 -07:00
truncate.c	page cache: use xa_lock	2018-04-11 10:28:39 -07:00
usercopy.c	usercopy: Allow boot cmdline disabling of hardening	2018-07-04 08:04:52 -07:00
userfaultfd.c	userfaultfd: prevent non-cooperative events vs mcopy_atomic races	2018-06-07 17:34:38 -07:00
util.c	mm/util: add kernel-doc for kvfree	2018-08-23 18:48:43 -07:00
vmacache.c	mm, vmacache: hash addresses based on pmd	2018-08-17 16:20:32 -07:00
vmalloc.c	mm: provide a fallback for PAGE_KERNEL_EXEC for architectures	2018-08-17 16:20:29 -07:00
vmpressure.c	mm/vmpressure.c: convert to use match_string() helper	2018-06-07 17:34:36 -07:00
vmscan.c	mm: fix page_freeze_refs and page_unfreeze_refs in comments	2018-08-22 10:52:44 -07:00
vmstat.c	Revert mm/vmstat.c: fix vmstat_update() preemption BUG	2018-06-28 11:16:44 -07:00
workingset.c	mm/list_lru: introduce list_lru_shrink_walk_irq()	2018-08-17 16:20:32 -07:00
z3fold.c	z3fold: fix reclaim lock-ups	2018-05-11 17:28:45 -07:00
zbud.c	…
zpool.c	…
zsmalloc.c	mm/zsmalloc.c: make several functions and a struct static	2018-08-17 16:20:30 -07:00
zswap.c	zswap: re-check zswap_is_full() after do zswap_shrink()	2018-07-26 19:38:03 -07:00