Commit graph

116 commits

Author SHA1 Message Date
Tejun Heo
833af8427b percpu: restructure pcpu_extend_area_map() to fix bugs and improve readability
pcpu_extend_area_map() had the following two bugs.

* It should return 1 if pcpu_lock was dropped and reacquired but it
  returned 0.  This could lead to oops if free_percpu() races with
  area map extension.

* pcpu_mem_free() was called under pcpu_lock.  pcpu_mem_free() might
  end up calling vfree() which isn't IRQ safe.  This could lead to
  deadlock through lock order inversion via IRQ.

In addition, Linus pointed out that the temporary lock dropping and
subtle three-way return value of pcpu_extend_area_map() was very ugly
and suggested to split the function into two - pcpu_need_to_extend()
and pcpu_extend_area_map().

This patch restructures pcpu_extend_area_map() as suggested and fixes
the two bugs.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
2009-11-13 00:55:35 +09:00
Tejun Heo
0f5e4816db percpu: remove some sparse warnings
Make the following changes to remove some sparse warnings.

* Make DEFINE_PER_CPU_SECTION() declare __pcpu_unique_* before
  defining it.

* Annotate pcpu_extend_area_map() that it is entered with pcpu_lock
  held, releases it and then reacquires it.

* Make percpu related macros use unique nested variable names.

* While at it, add pcpu prefix to __size_call[_return]() macros as
  to-be-implemented sparse annotations will add percpu specific stuff
  to these macros.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
2009-10-29 22:34:12 +09:00
Jiri Kosina
403a91b165 percpu: allow pcpu_alloc() to be called with IRQs off
pcpu_alloc() and pcpu_extend_area_map() perform a series of
spin_lock_irq()/spin_unlock_irq() calls, which make them unsafe
with respect to being called from contexts which have IRQs off.

This patch converts the code to perform save/restore of flags instead,
making pcpu_alloc() (or __alloc_percpu() respectively) to be called
from early kernel startup stage, where IRQs are off.

This is needed for proper initialization of per-cpu rq_weight data from
sched_init().

tj: added comment explaining why irqsave/restore is used in alloc path.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Tejun Heo <tj@kernel.org>
2009-10-29 00:25:59 +09:00
Tejun Heo
b7a4c946d0 Merge branch 'for-linus' into for-next 2009-10-12 17:14:18 +09:00
Tejun Heo
1a0c3298d6 percpu: fix compile warnings
Fix the following two compile warnings which show up on i386.

mm/percpu.c:1873: warning: comparison of distinct pointer types lacks a cast
mm/percpu.c:1879: warning: format '%lx' expects type 'long unsigned int', but argument 2 has type 'size_t'

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
2009-10-12 17:04:42 +09:00
Tejun Heo
23fb064bb9 percpu: kill legacy percpu allocator
With ia64 converted, there's no arch left which still uses legacy
percpu allocator.  Kill it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Delightedly-acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
2009-10-02 13:29:29 +09:00
Tejun Heo
f2badb0c95 percpu: make allocation failures more verbose
Warn and dump stack when percpu allocation fails.  percpu allocator is
still young and unchecked NULL percpu pointer usage can result in
random memory corruption when combined with the pointer shifting in
access macros.  Allocation failures should be rare and the warning
message will be disabled after certain times.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-09-29 09:17:58 +09:00
Tejun Heo
635b75fc18 percpu: make pcpu_setup_first_chunk() failures more verbose
The parameters to pcpu_setup_first_chunk() come from different sources
depending on architecture and can be quite complex.  The function runs
various sanity checks on the parameters and triggers BUG() if
something isn't right.  However, this is very early during the boot
and not reporting exactly what the problem is makes debugging even
harder.

Add PCPU_SETUP_BUG() macro which prints out enough information about
the parameters.  As the macro still puts separate BUG() for each
check, it won't lose any information even on the situations where only
the program counter can be retrieved.

While at it, also bump pcpu_dump_alloc_info() message to KERN_INFO so
that it's visible on the console if boot fails to complete.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-09-29 09:17:57 +09:00
Tejun Heo
6ea529a203 percpu: make embedding first chunk allocator check vmalloc space size
Embedding first chunk allocator maintains the distances between units
in the vmalloc area and thus needs vmalloc space to be larger than the
maximum distances between units; otherwise, it wouldn't be able to
create any dynamic chunks.  This patch makes the embedding first chunk
allocator check vmalloc space size and if the maximum distance between
units is larger than 75% of it, print warning and, if page mapping
allocator is available, fail initialization so that the system falls
back onto it.

This should work around percpu allocation failure problems on certain
sparc64 configurations where distances between NUMA nodes are larger
than the vmalloc area and makes percpu allocator more robust for
future configurations.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-09-29 09:17:57 +09:00
Tejun Heo
fb59e72e7e percpu: make pcpu_build_alloc_info() clear static buffers
pcpu_build_alloc_info() may be called multiple times when percpu is
falling back to different first chunk allocator.  Make it clear static
buffers so that they don't contain values from previous runs.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-09-29 09:17:57 +09:00
Tejun Heo
ffe0d5a575 percpu: fix unit_map[] verification in pcpu_setup_first_chunk()
pcpu_setup_first_chunk() incorrectly used NR_CPUS as the impossible
unit number while unit number can equal and go over NR_CPUS with
sparse unit map.  This triggers BUG_ON() spuriously on machines which
have non-power-of-two number of cpus.  Use UINT_MAX instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Tony Vroon <tony@linx.net>
2009-09-29 09:17:56 +09:00
Tejun Heo
5579fd7e6a Merge branch 'for-next' into for-linus
* pcpu_chunk_page_occupied() doesn't exist in for-next.
* pcpu_chunk_addr_search() updated to use raw_smp_processor_id().

Conflicts:
	mm/percpu.c
2009-09-15 09:57:19 +09:00
Tejun Heo
04a13c7c63 percpu: don't assume existence of cpu0
percpu incorrectly assumed that cpu0 was always there which led to the
following warning and eventual oops on sparc machines w/o cpu0.

  WARNING: at mm/percpu.c:651 pcpu_map+0xdc/0x100()
  Modules linked in:
  Call Trace:
    [000000000045eb70] warn_slowpath_common+0x50/0xa0
    [000000000045ebdc] warn_slowpath_null+0x1c/0x40
    [00000000004d493c] pcpu_map+0xdc/0x100
    [00000000004d59a4] pcpu_alloc+0x3e4/0x4e0
    [00000000004d5af8] __alloc_percpu+0x18/0x40
    [00000000005b112c] __percpu_counter_init+0x4c/0xc0
  ...
  Unable to handle kernel NULL pointer dereference
  ...
   I7: <sysfs_new_dirent+0x30/0x120>
   Disabling lock debugging due to kernel taint
   Caller[000000000053c1b0]: sysfs_new_dirent+0x30/0x120
   Caller[000000000053c7a4]: create_dir+0x24/0xc0
   Caller[000000000053c870]: sysfs_create_dir+0x30/0x80
   Caller[00000000005990e8]: kobject_add_internal+0xc8/0x200
  ...
   Kernel panic - not syncing: Attempted to kill the idle task!

This patch fixes the problem by backporting parts from devel branch to
make percpu core not depend on the existence of cpu0.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Meelis Roos <mroos@linux.ee>
Cc: David Miller <davem@davemloft.net>
2009-09-01 21:23:18 +09:00
Tejun Heo
e933a73f48 percpu: kill lpage first chunk allocator
With x86 converted to embedding allocator, lpage doesn't have any user
left.  Kill it along with cpa handling code.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jan Beulich <JBeulich@novell.com>
2009-08-14 15:00:53 +09:00
Tejun Heo
c8826dd538 percpu: update embedding first chunk allocator to handle sparse units
Now that percpu core can handle very sparse units, given that vmalloc
space is large enough, embedding first chunk allocator can use any
memory to build the first chunk.  This patch teaches
pcpu_embed_first_chunk() about distances between cpus and to use
alloc/free callbacks to allocate node specific areas for each group
and use them for the first chunk.

This brings the benefits of embedding allocator to NUMA configurations
- no extra TLB pressure with the flexibility of unified dynamic
allocator and no need to restructure arch code to build memory layout
suitable for percpu.  With units put into atom_size aligned groups
according to cpu distances, using large page for dynamic chunks is
also easily possible with falling back to reuglar pages if large
allocation fails.

Embedding allocator users are converted to specify NULL
cpu_distance_fn, so this patch doesn't cause any visible behavior
difference.  Following patches will convert them.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-08-14 15:00:52 +09:00
Tejun Heo
6563297cea percpu: use group information to allocate vmap areas sparsely
ai->groups[] contains which units need to be put consecutively and at
what offset from the chunk base address.  Compile this information
into pcpu_group_offsets[] and pcpu_group_sizes[] in
pcpu_setup_first_chunk() and use them to allocate sparse vm areas
using pcpu_get_vm_areas().

This will be used to allow directly using sparse NUMA memories as
percpu areas.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Nick Piggin <npiggin@suse.de>
2009-08-14 15:00:52 +09:00
Tejun Heo
bba174f5e0 percpu: add chunk->base_addr
The only thing percpu allocator wants to know about a vmalloc area is
the base address.  Instead of requiring chunk->vm, add
chunk->base_addr which contains the necessary value.  This simplifies
the code a bit and makes the dummy first_vm unnecessary.  This change
will ease allowing a chunk to be mapped by multiple vms.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-08-14 15:00:51 +09:00
Tejun Heo
fb435d5233 percpu: add pcpu_unit_offsets[]
Currently units are mapped sequentially into address space.  This
patch adds pcpu_unit_offsets[] which allows units to be mapped to
arbitrary offsets from the chunk base address.  This is necessary to
allow sparse embedding which might would need to allocate address
ranges and memory areas which aren't aligned to unit size but
allocation atom size (page or large page size).  This also simplifies
things a bit by removing the need to calculate offset from unit
number.

With this change, there's no need for the arch code to know
pcpu_unit_size.  Update pcpu_setup_first_chunk() and first chunk
allocators to return regular 0 or -errno return code instead of unit
size or -errno.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
2009-08-14 15:00:51 +09:00
Tejun Heo
fd1e8a1fe2 percpu: introduce pcpu_alloc_info and pcpu_group_info
Till now, non-linear cpu->unit map was expressed using an integer
array which maps each cpu to a unit and used only by lpage allocator.
Although how many units have been placed in a single contiguos area
(group) is known while building unit_map, the information is lost when
the result is recorded into the unit_map array.  For lpage allocator,
as all allocations are done by lpages and whether two adjacent lpages
are in the same group or not is irrelevant, this didn't cause any
problem.  Non-linear cpu->unit mapping will be used for sparse
embedding and this grouping information is necessary for that.

This patch introduces pcpu_alloc_info which contains all the
information necessary for initializing percpu allocator.
pcpu_alloc_info contains array of pcpu_group_info which describes how
units are grouped and mapped to cpus.  pcpu_group_info also has
base_offset field to specify its offset from the chunk's base address.
pcpu_build_alloc_info() initializes this field as if all groups are
allocated back-to-back as is currently done but this will be used to
sparsely place groups.

pcpu_alloc_info is a rather complex data structure which contains a
flexible array which in turn points to nested cpu_map arrays.

* pcpu_alloc_alloc_info() and pcpu_free_alloc_info() are provided to
  help dealing with pcpu_alloc_info.

* pcpu_lpage_build_unit_map() is updated to build pcpu_alloc_info,
  generalized and renamed to pcpu_build_alloc_info().
  @cpu_distance_fn may be NULL indicating that all cpus are of
  LOCAL_DISTANCE.

* pcpul_lpage_dump_cfg() is updated to process pcpu_alloc_info,
  generalized and renamed to pcpu_dump_alloc_info().  It now also
  prints which group each alloc unit belongs to.

* pcpu_setup_first_chunk() now takes pcpu_alloc_info instead of the
  separate parameters.  All first chunk allocators are updated to use
  pcpu_build_alloc_info() to build alloc_info and call
  pcpu_setup_first_chunk() with it.  This has the side effect of
  packing units for sparse possible cpus.  ie. if cpus 0, 2 and 4 are
  possible, they'll be assigned unit 0, 1 and 2 instead of 0, 2 and 4.

* x86 setup_pcpu_lpage() is updated to deal with alloc_info.

* sparc64 setup_per_cpu_areas() is updated to build alloc_info.

Although the changes made by this patch are pretty pervasive, it
doesn't cause any behavior difference other than packing of sparse
cpus.  It mostly changes how information is passed among
initialization functions and makes room for more flexibility.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
2009-08-14 15:00:51 +09:00
Tejun Heo
033e48fb82 percpu: move pcpu_lpage_build_unit_map() and pcpul_lpage_dump_cfg() upward
Unit map handling will be generalized and extended and used for
embedding sparse first chunk and other purposes.  Relocate two
unit_map related functions upward in preparation.  This patch just
moves the code without any actual change.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-08-14 15:00:51 +09:00
Tejun Heo
3cbc856527 percpu: add @align to pcpu_fc_alloc_fn_t
pcpu_fc_alloc_fn_t is about to see more interesting usage, add @align
parameter.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-08-14 15:00:50 +09:00
Tejun Heo
1d9d325721 percpu: make @dyn_size mandatory for pcpu_setup_first_chunk()
Now that all actual first chunk allocation and copying happen in the
first chunk allocators and helpers, there's no reason for
pcpu_setup_first_chunk() to try to determine @dyn_size automatically.
The only left user is page first chunk allocator.  Make it determine
dyn_size like other allocators and make @dyn_size mandatory for
pcpu_setup_first_chunk().

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-08-14 15:00:50 +09:00
Tejun Heo
9a7737691e percpu: drop @static_size from first chunk allocators
First chunk allocators assume percpu areas have been linked using one
of PERCPU_*() macros and depend on __per_cpu_load symbol defined by
those macros, so there isn't much point in passing in static area size
explicitly when it can be easily calculated from __per_cpu_start and
__per_cpu_end.  Drop @static_size from all percpu first chunk
allocators and helpers.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-08-14 15:00:50 +09:00
Tejun Heo
f58dc01ba2 percpu: generalize first chunk allocator selection
Now that all first chunk allocators are in mm/percpu.c, it makes sense
to make generalize percpu_alloc kernel parameter.  Define PCPU_FC_*
and set pcpu_chosen_fc using early_param() in mm/percpu.c.  Arch code
can use the set value to determine which first chunk allocator to use.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-08-14 15:00:50 +09:00
Tejun Heo
08fc458061 percpu: build first chunk allocators selectively
There's no need to build unused first chunk allocators in.  Define
CONFIG_NEED_PER_CPU_*_FIRST_CHUNK and let archs enable them
selectively.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-08-14 15:00:49 +09:00
Tejun Heo
00ae4064b1 percpu: rename 4k first chunk allocator to page
Page size isn't always 4k depending on arch and configuration.  Rename
4k first chunk allocator to page.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: David Howells <dhowells@redhat.com>
2009-08-14 15:00:49 +09:00
Tejun Heo
004018e2c0 percpu: improve boot messages
Improve percpu boot messages such that they're uniform and contain
more information.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
2009-08-14 15:00:49 +09:00
Tejun Heo
971f3918a5 percpu: fix pcpu_reclaim() locking
pcpu_reclaim() calls pcpu_depopulate_chunk() which makes use of pages
array and bitmap returned by pcpu_get_pages_and_bitmap() and thus
should be called under pcpu_alloc_mutex.  pcpu_reclaim() released the
mutex before calling depopulate leading to double free and other
strange problems caused by the unexpected concurrent usages of pages
array and bitmap.  Fix it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
2009-08-14 15:00:49 +09:00
Tejun Heo
384be2b18a Merge branch 'percpu-for-linus' into percpu-for-next
Conflicts:
	arch/sparc/kernel/smp_64.c
	arch/x86/kernel/cpu/perf_counter.c
	arch/x86/kernel/setup_percpu.c
	drivers/cpufreq/cpufreq_ondemand.c
	mm/percpu.c

Conflicts in core and arch percpu codes are mostly from commit
ed78e1e078dd44249f88b1dd8c76dafb39567161 which substituted many
num_possible_cpus() with nr_cpu_ids.  As for-next branch has moved all
the first chunk allocators into mm/percpu.c, the changes are moved
from arch code to mm/percpu.c.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-08-14 14:45:31 +09:00
Amerigo Wang
142d44b0dd percpu: use the right flag for get_vm_area()
get_vm_area() only accepts VM_* flags, not GFP_*.

And according to the doc of get_vm_area(), here should be
VM_ALLOC.

Signed-off-by: WANG Cong <amwang@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
2009-08-14 13:21:10 +09:00
Tejun Heo
74d46d6b2d percpu, sparc64: fix sparse possible cpu map handling
percpu code has been assuming num_possible_cpus() == nr_cpu_ids which
is incorrect if cpu_possible_map contains holes.  This causes percpu
code to access beyond allocated memories and vmalloc areas.  On a
sparc64 machine with cpus 0 and 2 (u60), this triggers the following
warning or fails boot.

 WARNING: at /devel/tj/os/work/mm/vmalloc.c:106 vmap_page_range_noflush+0x1f0/0x240()
 Modules linked in:
 Call Trace:
  [00000000004b17d0] vmap_page_range_noflush+0x1f0/0x240
  [00000000004b1840] map_vm_area+0x20/0x60
  [00000000004b1950] __vmalloc_area_node+0xd0/0x160
  [0000000000593434] deflate_init+0x14/0xe0
  [0000000000583b94] __crypto_alloc_tfm+0xd4/0x1e0
  [00000000005844f0] crypto_alloc_base+0x50/0xa0
  [000000000058b898] alg_test_comp+0x18/0x80
  [000000000058dad4] alg_test+0x54/0x180
  [000000000058af00] cryptomgr_test+0x40/0x60
  [0000000000473098] kthread+0x58/0x80
  [000000000042b590] kernel_thread+0x30/0x60
  [0000000000472fd0] kthreadd+0xf0/0x160
 ---[ end trace 429b268a213317ba ]---

This patch fixes generic percpu functions and sparc64
setup_per_cpu_areas() so that they handle sparse cpu_possible_map
properly.

Please note that on x86, cpu_possible_map() doesn't contain holes and
thus num_possible_cpus() == nr_cpu_ids and this patch doesn't cause
any behavior difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
2009-08-14 13:20:53 +09:00
Tejun Heo
a530b79586 percpu: teach large page allocator about NUMA
Large page first chunk allocator is primarily used for NUMA machines;
however, its NUMA handling is extremely simplistic.  Regardless of
their proximity, each cpu is put into separate large page just to
return most of the allocated space back wasting large amount of
vmalloc space and increasing cache footprint.

This patch teachs NUMA details to large page allocator.  Given
processor proximity information, pcpu_lpage_build_unit_map() will find
fitting cpu -> unit mapping in which cpus in LOCAL_DISTANCE share the
same large page and not too much virtual address space is wasted.

This greatly reduces the unit and thus chunk size and wastes much less
address space for the first chunk.  For example, on 4/4 NUMA machine,
the original code occupied 16MB of virtual space for the first chunk
while the new code only uses 4MB - one 2MB page for each node.

[ Impact: much better space efficiency on NUMA machines ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Miller <davem@davemloft.net>
2009-07-04 08:11:00 +09:00
Tejun Heo
2f39e637ea percpu: allow non-linear / sparse cpu -> unit mapping
Currently cpu and unit are always identity mapped.  To allow more
efficient large page support on NUMA and lazy allocation for possible
but offline cpus, cpu -> unit mapping needs to be non-linear and/or
sparse.  This can be easily implemented by adding a cpu -> unit
mapping array and using it whenever looking up the matching unit for a
cpu.

The only unusal conversion is in pcpu_chunk_addr_search().  The passed
in address is unit0 based and unit0 might not be in use so it needs to
be converted to address of an in-use unit.  This is easily done by
adding the unit offset for the current processor.

[ Impact: allows non-linear/sparse cpu -> unit mapping, no visible change yet ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
2009-07-04 08:11:00 +09:00
Tejun Heo
ce3141a277 percpu: drop pcpu_chunk->page[]
percpu core doesn't need to tack all the allocated pages.  It needs to
know whether certain pages are populated and a way to reverse map
address to page when freeing.  This patch drops pcpu_chunk->page[] and
use populated bitmap and vmalloc_to_page() lookup instead.  Using
vmalloc_to_page() exclusively is also possible but complicates first
chunk handling, inflates cache footprint and prevents non-standard
memory allocation for percpu memory.

pcpu_chunk->page[] was used to track each page's allocation and
allowed asymmetric population which happens during failure path;
however, with single bitmap for all units, this is no longer possible.
Bite the bullet and rewrite (de)populate functions so that things are
done in clearly separated steps such that asymmetric population
doesn't happen.  This makes the (de)population process much more
modular and will also ease implementing non-standard memory usage in
the future (e.g. large pages).

This makes @get_page_fn parameter to pcpu_setup_first_chunk()
unnecessary.  The parameter is dropped and all first chunk helpers are
updated accordingly.  Please note that despite the volume most changes
to first chunk helpers are symbol renames for variables which don't
need to be referenced outside of the helper anymore.

This change reduces memory usage and cache footprint of pcpu_chunk.
Now only #unit_pages bits are necessary per chunk.

[ Impact: reduced memory usage and cache footprint for bookkeeping ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: David Miller <davem@davemloft.net>
2009-07-04 08:11:00 +09:00
Tejun Heo
c8a51be4ca percpu: reorder a few functions in mm/percpu.c
(de)populate functions are about to be reimplemented to drop
pcpu_chunk->page array.  Move a few functions so that the rewrite
patch doesn't have code movement making it more difficult to read.

[ Impact: code movement ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
2009-07-04 08:10:59 +09:00
Tejun Heo
38a6be5254 percpu: simplify pcpu_setup_first_chunk()
Now that all first chunk allocator helpers allocate and map the first
chunk themselves, there's no need to have optional default alloc/map
in pcpu_setup_first_chunk().  Drop @populate_pte_fn and only leave
@dyn_size optional and make all other params mandatory.

This makes it much easier to follow what pcpu_setup_first_chunk() is
doing and what actual differences tweaking each parameter results in.

[ Impact: drop unused code path ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
2009-07-04 08:10:59 +09:00
Tejun Heo
8c4bfc6e88 x86,percpu: generalize lpage first chunk allocator
Generalize and move x86 setup_pcpu_lpage() into
pcpu_lpage_first_chunk().  setup_pcpu_lpage() now is a simple wrapper
around the generalized version.  Other than taking size parameters and
using arch supplied callbacks to allocate/free/map memory,
pcpu_lpage_first_chunk() is identical to the original implementation.

This simplifies arch code and will help converting more archs to
dynamic percpu allocator.

While at it, factor out pcpu_calc_fc_sizes() which is common to
pcpu_embed_first_chunk() and pcpu_lpage_first_chunk().

[ Impact: code reorganization and generalization ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
2009-07-04 08:10:59 +09:00
Tejun Heo
8f05a6a65d percpu: make 4k first chunk allocator map memory
At first, percpu first chunk was always setup page-by-page by the
generic code.  To add other allocators, different parts of the generic
initialization was made optional.  Now we have three allocators -
embed, remap and 4k.  embed and remap fully handle allocation and
mapping of the first chunk while 4k still depends on generic code for
those.  This makes the generic alloc/map paths specifci to 4k and
makes the code unnecessary complicated with optional generic
behaviors.

This patch makes the 4k allocator to allocate and map memory directly
instead of depending on the generic code.  The only outside visible
change is that now dynamic area in the first chunk is allocated
up-front instead of on-demand.  This doesn't make any meaningful
difference as the area is minimal (usually less than a page, just
enough to fill the alignment) on 4k allocator.  Plus, dynamic area in
the first chunk usually gets fully used anyway.

This will allow simplification of pcpu_setpu_first_chunk() and removal
of chunk->page array.

[ Impact: no outside visible change other than up-front allocation of dyn area ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
2009-07-04 08:10:59 +09:00
Tejun Heo
d4b95f8039 x86,percpu: generalize 4k first chunk allocator
Generalize and move x86 setup_pcpu_4k() into pcpu_4k_first_chunk().
setup_pcpu_4k() now is a simple wrapper around the generalized
version.  Other than taking size parameters and using arch supplied
callbacks to allocate/free memory, pcpu_4k_first_chunk() is identical
to the original implementation.

This simplifies arch code and will help converting more archs to
dynamic percpu allocator.

While at it, s/pcpu_populate_pte_fn_t/pcpu_fc_populate_pte_fn_t/ for
consistency.

[ Impact: code reorganization and generalization ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
2009-07-04 08:10:59 +09:00
Tejun Heo
788e5abc54 percpu: drop @unit_size from embed first chunk allocator
The only extra feature @unit_size provides is making dead space at the
end of the first chunk which doesn't have any valid usecase.  Drop the
parameter.  This will increase consistency with generalized 4k
allocator.

James Bottomley spotted missing conversion for the default
setup_per_cpu_areas() which caused build breakage on all arcsh which
use it.

[ Impact: drop unused code path ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Ingo Molnar <mingo@elte.hu>
2009-07-04 08:10:58 +09:00
Tejun Heo
79ba6ac825 x86: make pcpu_chunk_addr_search() matching stricter
The @addr passed into pcpu_chunk_addr_search() is unit0 based address
and thus should be matched inside unit0 area.  Currently, when it uses
chunk size when determining whether the address falls in the first
chunk.  Addresses in unitN where N>0 shouldn't be passed in anyway, so
this doesn't cause any malfunction but fix it for consistency.

[ Impact: mostly cleanup ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
2009-07-04 08:10:58 +09:00
Tejun Heo
e74e396204 percpu: use dynamic percpu allocator as the default percpu allocator
This patch makes most !CONFIG_HAVE_SETUP_PER_CPU_AREA archs use
dynamic percpu allocator.  The first chunk is allocated using
embedding helper and 8k is reserved for modules.  This ensures that
the new allocator behaves almost identically to the original allocator
as long as static percpu variables are concerned, so it shouldn't
introduce much breakage.

s390 and alpha use custom SHIFT_PERCPU_PTR() to work around addressing
range limit the addressing model imposes.  Unfortunately, this breaks
if the address is specified using a variable, so for now, the two
archs aren't converted.

The following architectures are affected by this change.

* sh
* arm
* cris
* mips
* sparc(32)
* blackfin
* avr32
* parisc (broken, under investigation)
* m32r
* powerpc(32)

As this change makes the dynamic allocator the default one,
CONFIG_HAVE_DYNAMIC_PER_CPU_AREA is replaced with its invert -
CONFIG_HAVE_LEGACY_PER_CPU_AREA, which is added to yet-to-be converted
archs.  These archs implement their own setup_per_cpu_areas() and the
conversion is not trivial.

* powerpc(64)
* sparc(64)
* ia64
* alpha
* s390

Boot and batch alloc/free tests on x86_32 with debug code (x86_32
doesn't use default first chunk initialization).  Compile tested on
sparc(32), powerpc(32), arm and alpha.

Kyle McMartin reported that this change breaks parisc.  The problem is
still under investigation and he is okay with pushing this patch
forward and fixing parisc later.

[ Impact: use dynamic allocator for most archs w/o custom percpu setup ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Bryan Wu <cooloney@kernel.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Grant Grundler <grundler@parisc-linux.org>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
2009-06-24 15:13:35 +09:00
Tejun Heo
fa8a7094ba x86: implement percpu_alloc kernel parameter
According to Andi, it isn't clear whether lpage allocator is worth the
trouble as there are many processors where PMD TLB is far scarcer than
PTE TLB.  The advantage or disadvantage probably depends on the actual
size of percpu area and specific processor.  As performance
degradation due to TLB pressure tends to be highly workload specific
and subtle, it is difficult to decide which way to go without more
data.

This patch implements percpu_alloc kernel parameter to allow selecting
which first chunk allocator to use to ease debugging and testing.

While at it, make sure all the failure paths report why something
failed to help determining why certain allocator isn't working.  Also,
kill the "Great future plan" comment which had already been realized
quite some time ago.

[ Impact: allow explicit percpu first chunk allocator selection ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jan Beulich <JBeulich@novell.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Ingo Molnar <mingo@elte.hu>
2009-06-22 11:56:24 +09:00
Tejun Heo
85ae87c1ad percpu: fix too lazy vunmap cache flushing
In pcpu_unmap(), flushing virtual cache on vunmap can't be delayed as
the page is going to be returned to the page allocator.  Only TLB
flushing can be put off such that vmalloc code can handle it lazily.
Fix it.

[ Impact: fix subtle virtual cache flush bug ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
2009-06-22 11:56:23 +09:00
Christoph Lameter
e1b9aa3f47 percpu: remove rbtree and use page->index instead
Impact: use page->index for addr to chunk mapping instead of dedicated rbtree

The rbtree is used to determine the chunk from the virtual address.
However, we can already determine the page struct from a virtual
address and there are several unused fields in page struct used by
vmalloc.  Use the index field to store a pointer to the chunk. Then
there is no need anymore for an rbtree.

tj: * s/(set|get)_chunk/pcpu_\1_page_chunk/

    * Drop inline from the above two functions and moved them upwards
      so that they are with other simple helpers.

    * Initial pages might not (actually most of the time don't) live
      in the vmalloc area.  With the previous patch to manually
      reverse-map both first chunks, this is no longer an issue.
      Removed pcpu_set_chunk() call on initial pages.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: rusty@rustcorp.com.au
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: rmk@arm.linux.org.uk
Cc: starvik@axis.com
Cc: ralf@linux-mips.org
Cc: davem@davemloft.net
Cc: cooloney@kernel.org
Cc: kyle@mcmartin.ca
Cc: matthew@wil.cx
Cc: grundler@parisc-linux.org
Cc: takata@linux-m32r.org
Cc: benh@kernel.crashing.org
Cc: rth@twiddle.net
Cc: ink@jurassic.park.msu.ru
Cc: heiko.carstens@de.ibm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>
LKML-Reference: <49D43D58.4050102@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-08 18:31:31 +02:00
Tejun Heo
ae9e6bc9f7 percpu: don't put the first chunk in reverse-map rbtree
Impact: both first chunks don't use rbtree, no functional change

There can be two first chunks - reserved and dynamic with the former
one being optional.  Dynamic first chunk was linked on reverse-mapping
rbtree while the reserved one was mapped manually using the start
address and reserved offset limit.

This patch makes both first chunks to be looked up manually without
using the rbtree.  This is to help getting rid of the rbtree.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: rusty@rustcorp.com.au
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: rmk@arm.linux.org.uk
Cc: starvik@axis.com
Cc: ralf@linux-mips.org
Cc: davem@davemloft.net
Cc: cooloney@kernel.org
Cc: kyle@mcmartin.ca
Cc: matthew@wil.cx
Cc: grundler@parisc-linux.org
Cc: takata@linux-m32r.org
Cc: benh@kernel.crashing.org
Cc: rth@twiddle.net
Cc: ink@jurassic.park.msu.ru
Cc: heiko.carstens@de.ibm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Christoph Lameter <cl@linux.com>
LKML-Reference: <49D43CEA.3040609@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-08 18:31:30 +02:00
Tejun Heo
66c3a75772 percpu: generalize embedding first chunk setup helper
Impact: code reorganization

Separate out embedding first chunk setup helper from x86 embedding
first chunk allocator and put it in mm/percpu.c.  This will be used by
the default percpu first chunk allocator and possibly by other archs.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-10 16:27:48 +09:00
Tejun Heo
6074d5b0a3 percpu: more flexibility for @dyn_size of pcpu_setup_first_chunk()
Impact: cleanup, more flexibility for first chunk init

Non-negative @dyn_size used to be allowed iff @unit_size wasn't auto.
This restriction stemmed from implementation detail and made things a
bit less intuitive.  This patch allows @dyn_size to be specified
regardless of @unit_size and swaps the positions of @dyn_size and
@unit_size so that the parameter order makes more sense (static,
reserved and dyn sizes followed by enclosing unit_size).

While at it, add @unit_size >= PCPU_MIN_UNIT_SIZE sanity check.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-10 16:27:48 +09:00
Tejun Heo
e01009833e percpu: make x86 addr <-> pcpu ptr conversion macros generic
Impact: generic addr <-> pcpu ptr conversion macros

There's nothing arch specific about x86 __addr_to_pcpu_ptr() and
__pcpu_ptr_to_addr().  With proper __per_cpu_load and __per_cpu_start
defined, they'll do the right thing regardless of actual layout.

Move these macros from arch/x86/include/asm/percpu.h to mm/percpu.c
and allow archs to override it as necessary.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-10 16:27:48 +09:00
Tejun Heo
ccea34b5d0 percpu: finer grained locking to break deadlock and allow atomic free
Impact: fix deadlock and allow atomic free

Percpu allocation always uses GFP_KERNEL and whole alloc/free paths
were protected by single mutex.  All percpu allocations have been from
GFP_KERNEL-safe context and the original allocator had this assumption
too.  However, by protecting both alloc and free paths with the same
mutex, the new allocator creates free -> alloc -> GFP_KERNEL
dependency which the original allocator didn't have.  This can lead to
deadlock if free is called from FS or IO paths.  Also, in general,
allocators are expected to allow free to be called from atomic
context.

This patch implements finer grained locking to break the deadlock and
allow atomic free.  For details, please read the "Synchronization
rules" comment.

While at it, also add CONTEXT: to function comments to describe which
context they expect to be called from and what they do to it.

This problem was reported by Thomas Gleixner and Peter Zijlstra.

  http://thread.gmane.org/gmane.linux.kernel/802384

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Peter Zijlstra <peterz@infradead.org>
2009-03-07 14:46:35 +09:00
Tejun Heo
a56dbddf06 percpu: move fully free chunk reclamation into a work
Impact: code reorganization for later changes

Do fully free chunk reclamation using a work.  This change is to
prepare for locking changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-07 00:44:11 +09:00
Tejun Heo
9f7dcf224b percpu: move chunk area map extension out of area allocation
Impact: code reorganization for later changes

Separate out chunk area map extension into a separate function -
pcpu_extend_area_map() - and call it directly from pcpu_alloc() such
that pcpu_alloc_area() is guaranteed to have enough area map slots on
invocation.

With this change, pcpu_alloc_area() does only area allocation and the
only failure mode is when the chunk doens't have enough room, so
there's no need to distinguish it from memory allocation failures.
Make it return -1 on such cases instead of hacky -ENOSPC.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-07 00:44:09 +09:00
Tejun Heo
1880d93b80 percpu: replace pcpu_realloc() with pcpu_mem_alloc() and pcpu_mem_free()
Impact: code reorganization for later changes

With static map handling moved to pcpu_split_block(), pcpu_realloc()
only clutters the code and it's also unsuitable for scheduled locking
changes.  Implement and use pcpu_mem_alloc/free() instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-07 00:44:09 +09:00
Tejun Heo
edcb463997 percpu, module: implement reserved allocation and use it for module percpu variables
Impact: add reserved allocation functionality and use it for module
	percpu variables

This patch implements reserved allocation from the first chunk.  When
setting up the first chunk, arch can ask to set aside certain number
of bytes right after the core static area which is available only
through a separate reserved allocator.  This will be used primarily
for module static percpu variables on architectures with limited
relocation range to ensure that the module perpcu symbols are inside
the relocatable range.

If reserved area is requested, the first chunk becomes reserved and
isn't available for regular allocation.  If the first chunk also
includes piggy-back dynamic allocation area, a separate chunk mapping
the same region is created to serve dynamic allocation.  The first one
is called static first chunk and the second dynamic first chunk.
Although they share the page map, their different area map
initializations guarantee they serve disjoint areas according to their
purposes.

If arch doesn't setup reserved area, reserved allocation is handled
like any other allocation.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-06 14:33:59 +09:00
Tejun Heo
3e24aa5890 percpu: add an indirection ptr for chunk page map access
Impact: allow sharing page map, no functional difference yet

Make chunk->page access indirect by adding a pointer and renaming the
actual array to page_ar.  This will be used by future changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-06 14:33:59 +09:00
Tejun Heo
cafe8816b2 percpu: use negative for auto for pcpu_setup_first_chunk() arguments
Impact: argument semantic cleanup

In pcpu_setup_first_chunk(), zero @unit_size and @dyn_size meant
auto-sizing.  It's okay for @unit_size as 0 doesn't make sense but 0
dynamic reserve size is valid.  Alos, if arch @dyn_size is calculated
from other parameters, it might end up passing in 0 @dyn_size and
malfunction when the size is automatically adjusted.

This patch makes both @unit_size and @dyn_size ssize_t and use -1 for
auto sizing.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-06 14:33:59 +09:00
Tejun Heo
61ace7fa2f percpu: improve first chunk initial area map handling
Impact: no functional change

When the first chunk is created, its initial area map is not allocated
because kmalloc isn't online yet.  The map is allocated and
initialized on the first allocation request on the chunk.  This works
fine but the scattering of initialization logic between the init
function and allocation path is a bit confusing.

This patch makes the first chunk initialize and use minimal statically
allocated map from pcpu_setpu_first_chunk().  The map resizing path
still needs to handle this specially but it's more straight-forward
and gives more latitude to the init path.  This will ease future
changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-06 14:33:59 +09:00
Tejun Heo
2441d15c97 percpu: cosmetic renames in pcpu_setup_first_chunk()
Impact: cosmetic, preparation for future changes

Make the following renames in pcpur_setup_first_chunk() in preparation
for future changes.

* s/free_size/dyn_size/
* s/static_vm/first_vm/
* s/static_chunk/schunk/

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-03-06 14:33:59 +09:00
Tejun Heo
02d51fdfb2 percpu: kill compile warning in pcpu_populate_chunk()
Impact: remove compile warning

Mark local variable map_end in pcpu_populate_chunk() with
uninitialized_var().  The variable is always used in tandem with
map_start and guaranteed to be initialized before use but gcc doesn't
understand that.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Ingo Molnar <mingo@elte.hu>
2009-03-01 15:42:36 +09:00
Tejun Heo
40150d37be percpu: add __read_mostly to variables which are mostly read only
Most global variables in percpu allocator are initialized during boot
and read only from that point on.  Add __read_mostly as per Rusty's
suggestion.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
2009-02-24 14:24:30 +09:00
Tejun Heo
8d408b4be3 percpu: give more latitude to arch specific first chunk initialization
Impact: more latitude for first percpu chunk allocation

The first percpu chunk serves the kernel static percpu area and may or
may not contain extra room for further dynamic allocation.
Initialization of the first chunk needs to be done before normal
memory allocation service is up, so it has its own init path -
pcpu_setup_static().

It seems archs need more latitude while initializing the first chunk
for example to take advantage of large page mapping.  This patch makes
the following changes to allow this.

* Define PERCPU_DYNAMIC_RESERVE to give arch hint about how much space
  to reserve in the first chunk for further dynamic allocation.

* Rename pcpu_setup_static() to pcpu_setup_first_chunk().

* Make pcpu_setup_first_chunk() much more flexible by fetching page
  pointer by callback and adding optional @unit_size, @free_size and
  @base_addr arguments which allow archs to selectively part of chunk
  initialization to their likings.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-02-24 11:57:21 +09:00
Tejun Heo
d9b55eeb1d percpu: remove unit_size power-of-2 restriction
Impact: allow unit_size to be arbitrary multiple of PAGE_SIZE

In dynamic percpu allocator, there is no reason the unit size should
be power of two.  Remove the restriction.

As non-power-of-two unit size means that empty chunks fall into the
same slot index as lightly occupied chunks which is bad for reclaming.
Reserve an extra slot for empty chunks.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-02-24 11:57:21 +09:00
Tejun Heo
c0c0a29379 vmalloc: add @align to vm_area_register_early()
Impact: allow larger alignment for early vmalloc area allocation

Some early vmalloc users might want larger alignment, for example, for
custom large page mapping.  Add @align to vm_area_register_early().
While at it, drop docbook comment on non-existent @size.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
2009-02-24 11:57:21 +09:00
Tejun Heo
cb83b42e23 percpu: fix pcpu_chunk_struct_size
Impact: fix short allocation leading to memory corruption

While dropping rvalue wrapping macros around global parameters,
pcpu_chunk_struct_size was set incorrectly resulting in shorter page
pointer array.  Fix it.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-02-24 11:57:20 +09:00
Tejun Heo
cae3aeb83f percpu: clean up size usage
Andrew was concerned about the unit of variables named or have suffix
size.  Every usage in percpu allocator is in bytes but make it super
clear by adding comments.

While at it, make pcpu_depopulate_chunk() take int @off and @size like
everyone else.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
2009-02-21 16:56:23 +09:00
Tejun Heo
fbf59bc9d7 percpu: implement new dynamic percpu allocator
Impact: new scalable dynamic percpu allocator which allows dynamic
        percpu areas to be accessed the same way as static ones

Implement scalable dynamic percpu allocator which can be used for both
static and dynamic percpu areas.  This will allow static and dynamic
areas to share faster direct access methods.  This feature is optional
and enabled only when CONFIG_HAVE_DYNAMIC_PER_CPU_AREA is defined by
arch.  Please read comment on top of mm/percpu.c for details.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
2009-02-20 16:29:08 +09:00