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linux/mm
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Artem Bityutskiy fff5b85aa4 writeback: move bdi threads exiting logic to the forker thread 
Currently, bdi threads can decide to exit if there were no useful activities
for 5 minutes. However, this causes nasty races: we can easily oops in the
'bdi_queue_work()' if the bdi thread decides to exit while we are waking it up.

And even if we do not oops, but the bdi tread exits immediately after we wake
it up, we'd lose the wake-up event and have an unnecessary delay (up to 5 secs)
in the bdi work processing.

This patch makes the forker thread to be the central place which not only
creates bdi threads, but also kills them if they were inactive long enough.
This better design-wise.

Another reason why this change was done is to prepare for the further changes
which will prevent the bdi threads from waking up every 5 sec and wasting
power. Indeed, when the task does not wake up periodically anymore, it won't be
able to exit either.

This patch also moves the the 'wake_up_bit()' call from the bdi thread to the
forker thread as well. So now the forker thread sets the BDI_pending bit, then
forks the task or kills it, then clears the bit and wakes up the waiting
process.

The only process which may wain on the bit is 'bdi_wb_shutdown()'. This
function was changed as well - now it first removes the bdi from the
'bdi_list', then waits on the 'BDI_pending' bit. Once it wakes up, it is
guaranteed that the forker thread won't race with it, because the bdi is not
visible. Note, the forker thread sets the 'BDI_pending' bit under the
'bdi->wb_lock' which is essential for proper serialization.

And additionally, when we change 'bdi->wb.task', we now take the
'bdi->work_lock', to make sure that we do not lose wake-ups which we otherwise
would when raced with, say, 'bdi_queue_work()'.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-08-07 18:53:56 +02:00
..
backing-dev.c writeback: move bdi threads exiting logic to the forker thread 2010-08-07 18:53:56 +02:00
bootmem.c x86,nobootmem: make alloc_bootmem_node fall back to other node when 32bit numa is used 2010-07-20 16:25:40 -07:00
bounce.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
compaction.c mm: compaction: add a tunable that decides when memory should be compacted and when it should be reclaimed 2010-05-25 08:06:59 -07:00
debug-pagealloc.c generic debug pagealloc 2009-04-01 08:59:13 -07:00
dmapool.c dmapools: protect page_list walk in show_pools() 2009-06-30 18:56:00 -07:00
fadvise.c readahead: introduce FMODE_RANDOM for POSIX_FADV_RANDOM 2010-03-06 11:26:25 -08:00
failslab.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
filemap.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse 2010-05-30 09:16:14 -07:00
filemap_xip.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
fremap.c mm: clean up mm_counter 2010-03-06 11:26:23 -08:00
highmem.c highmem: remove unneeded #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT for debug_kmap_atomic() 2010-05-25 08:07:01 -07:00
hugetlb.c cpuset,mm: fix no node to alloc memory when changing cpuset's mems 2010-05-25 08:06:57 -07:00
hwpoison-inject.c HWPOISON: Don't do early filtering if filter is disabled 2009-12-16 12:20:01 +01:00
init-mm.c mm: consolidate init_mm definition 2009-06-16 19:47:28 -07:00
internal.h HWPOISON: add an interface to switch off/on all the page filters 2009-12-16 12:19:59 +01:00
Kconfig lmb: rename to memblock 2010-07-14 17:14:00 +10:00
Kconfig.debug trivial: improve help text for mm debug config options 2009-09-21 15:14:57 +02:00
kmemcheck.c kmemcheck: Fix build errors due to missing slab.h 2010-03-30 22:02:32 +09:00
kmemleak-test.c percpu: clean up percpu variable definitions 2009-06-24 15:13:48 +09:00
kmemleak.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
ksm.c mm: migration: share the anon_vma ref counts between KSM and page migration 2010-05-25 08:06:58 -07:00
maccess.c maccess,probe_kernel: Allow arch specific override probe_kernel_(read|write) 2010-01-07 11:58:36 -06:00
madvise.c HWPOISON: Add a madvise() injector for soft page offlining 2009-12-16 12:20:00 +01:00
Makefile lmb: rename to memblock 2010-07-14 17:14:00 +10:00
memblock.c lmb: rename to memblock 2010-07-14 17:14:00 +10:00
memcontrol.c memcg: fix wake up in oom wait queue 2010-06-29 15:29:30 -07:00
memory-failure.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
memory.c mm: fix ia64 crash when gcore reads gate area 2010-07-30 18:56:09 -07:00
memory_hotplug.c mem-hotplug: fix potential race while building zonelist for new populated zone 2010-05-25 08:07:02 -07:00
mempolicy.c mempolicy: fix dangling reference to tmpfs superblock mpol 2010-06-29 15:29:31 -07:00
mempool.c mm: remove broken 'kzalloc' mempool 2009-09-22 07:17:35 -07:00
migrate.c memcg: fix mis-accounting of file mapped racy with migration 2010-05-27 09:12:44 -07:00
mincore.c mincore: do nested page table walks 2010-05-25 08:06:58 -07:00
mlock.c x86, perf, bts, mm: Delete the never used BTS-ptrace code 2010-03-26 11:33:55 +01:00
mm_init.c mm: mminit_loglevel cannot be __meminitdata anymore 2008-08-20 15:40:30 -07:00
mmap.c mmap: check ->vm_ops before dereferencing 2010-04-27 08:26:51 -07:00
mmu_context.c exit: fix oops in sync_mm_rss 2010-03-24 16:31:21 -07:00
mmu_notifier.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
mmzone.c [ARM] Double check memmap is actually valid with a memmap has unexpected holes V2 2009-05-18 11:22:24 +01:00
mprotect.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
mremap.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
msync.c sanitize vfs_fsync calling conventions 2010-05-21 18:31:21 -04:00
nommu.c nommu: allow private mappings of read-only devices 2010-05-26 08:19:23 -07:00
oom_kill.c memcg: make oom killer a no-op when no killable task can be found 2010-05-27 09:12:43 -07:00
page-writeback.c writeback: Add tracing to write_cache_pages 2010-08-07 18:24:26 +02:00
page_alloc.c x86,nobootmem: make alloc_bootmem_node fall back to other node when 32bit numa is used 2010-07-20 16:25:40 -07:00
page_cgroup.c kmemleak: Annotate false positive in init_section_page_cgroup() 2010-07-19 11:54:14 +01:00
page_io.c block: unify flags for struct bio and struct request 2010-08-07 18:20:39 +02:00
page_isolation.c memory hotplug: fix page_zone() calculation in test_pages_isolated() 2008-11-06 15:41:19 -08:00
pagewalk.c pagemap: fix pfn calculation for hugepage 2010-04-07 08:38:04 -07:00
percpu-km.c percpu: implement kernel memory based chunk allocation 2010-05-01 08:30:50 +02:00
percpu-vm.c percpu: move vmalloc based chunk management into percpu-vm.c 2010-05-01 08:30:50 +02:00
percpu.c percpu: fix first chunk match in per_cpu_ptr_to_phys() 2010-06-18 15:07:23 +02:00
percpu_up.c percpu: don't implicitly include slab.h from percpu.h 2010-03-30 22:02:32 +09:00
prio_tree.c
quicklist.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
readahead.c readahead.c: fix comment 2010-05-25 08:07:00 -07:00
rmap.c mm: migration: avoid race between shift_arg_pages() and rmap_walk() during migration by not migrating temporary stacks 2010-05-25 08:06:59 -07:00
shmem.c fix truncate inode time modification breakage 2010-06-04 17:16:30 -04:00
slab.c numa: slab: use numa_mem_id() for slab local memory node 2010-05-27 09:12:57 -07:00
slob.c mm: Move ARCH_SLAB_MINALIGN and ARCH_KMALLOC_MINALIGN to <linux/slob_def.h> 2010-05-19 22:03:13 +03:00
slub.c Merge branch 'slub/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6 2010-05-30 12:46:17 -07:00
sparse-vmemmap.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
sparse.c sparsemem: on no vmemmap path put mem_map on node high too 2010-05-25 08:06:56 -07:00
swap.c mm: export lru_cache_add_*() to modules 2010-05-25 15:06:06 +02:00
swap_state.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
swapfile.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging-2.6 2010-05-21 15:26:46 -07:00
thrash.c mm: pass mm to grab_swap_token 2009-06-23 12:50:05 -07:00
truncate.c fs: introduce new truncate sequence 2010-05-27 22:15:33 -04:00
util.c slab: Generify kernel pointer validation 2010-04-09 10:09:50 -07:00
vmalloc.c mm: purge fragmented percpu vmap blocks 2010-02-02 12:50:47 -08:00
vmscan.c mm/vmscan.c: fix mapping use after free 2010-07-20 16:25:40 -07:00
vmstat.c mm: compaction: direct compact when a high-order allocation fails 2010-05-25 08:06:59 -07:00