History log of /openbmc/linux/block/blk-ioc.c (Results 376 – 400 of 634)
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# d4730ace 06-Feb-2012 Jiri Kosina <jkosina@suse.cz>

Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into upstream-fixes

Sync with Linus' tree. This is necessary to have a base for
patch that fixes commit 35b4c01e

Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into upstream-fixes

Sync with Linus' tree. This is necessary to have a base for
patch that fixes commit 35b4c01e29b ("power_supply: add "powers"
links to self-powered HID devices") which went in through Anton's
tree.

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# 9fa73472 06-Feb-2012 Shaohua Li <shaohua.li@intel.com>

block: fix ioc locking warning

Meelis reported a warning:

WARNING: at kernel/timer.c:1122 run_timer_softirq+0x199/0x1ec()
Hardware name: 939Dual-SATA2
timer: cfq_idle_slice_timer+0x0/0xaa preempt l

block: fix ioc locking warning

Meelis reported a warning:

WARNING: at kernel/timer.c:1122 run_timer_softirq+0x199/0x1ec()
Hardware name: 939Dual-SATA2
timer: cfq_idle_slice_timer+0x0/0xaa preempt leak: 00000102 -> 00000103
Modules linked in: sr_mod cdrom videodev media drm_kms_helper ohci_hcd ehci_hcd v4l2_compat_ioctl32 usbcore i2c_ali15x3 snd_seq drm snd_timer snd_seq
Pid: 0, comm: swapper Not tainted 3.3.0-rc2-00110-gd125666 #176
Call Trace:
<IRQ> [<ffffffff81022aaa>] warn_slowpath_common+0x7e/0x96
[<ffffffff8114c485>] ? cfq_slice_expired+0x1d/0x1d
[<ffffffff81022b56>] warn_slowpath_fmt+0x41/0x43
[<ffffffff8114c526>] ? cfq_idle_slice_timer+0xa1/0xaa
[<ffffffff8114c485>] ? cfq_slice_expired+0x1d/0x1d
[<ffffffff8102c124>] run_timer_softirq+0x199/0x1ec
[<ffffffff81047a53>] ? timekeeping_get_ns+0x12/0x31
[<ffffffff810145fd>] ? apic_write+0x11/0x13
[<ffffffff81027475>] __do_softirq+0x74/0xfa
[<ffffffff812f337a>] call_softirq+0x1a/0x30
[<ffffffff81002ff9>] do_softirq+0x31/0x68
[<ffffffff810276cf>] irq_exit+0x3d/0xa3
[<ffffffff81014aca>] smp_apic_timer_interrupt+0x6b/0x77
[<ffffffff812f2de9>] apic_timer_interrupt+0x69/0x70
<EOI> [<ffffffff81040136>] ? sched_clock_cpu+0x73/0x7d
[<ffffffff81040136>] ? sched_clock_cpu+0x73/0x7d
[<ffffffff8100801f>] ? default_idle+0x1e/0x32
[<ffffffff81008019>] ? default_idle+0x18/0x32
[<ffffffff810008b1>] cpu_idle+0x87/0xd1
[<ffffffff812de861>] rest_init+0x85/0x89
[<ffffffff81659a4d>] start_kernel+0x2eb/0x2f8
[<ffffffff8165926e>] x86_64_start_reservations+0x7e/0x82
[<ffffffff81659362>] x86_64_start_kernel+0xf0/0xf7

this_q == locked_q is possible. There are two problems here:
1. In UP case, there is preemption counter issue as spin_trylock always
successes.
2. In SMP case, the loop breaks too earlier.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Reported-by: Meelis Roos <mroos@linux.ee>
Reported-by: Knut Petersen <Knut_Petersen@t-online.de>
Tested-by: Knut Petersen <Knut_Petersen@t-online.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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# 972c5ae9 03-Feb-2012 Jiri Kosina <jkosina@suse.cz>

Merge branch 'master' into for-next

Sync with Linus' tree to be able to apply patch to a newer
code (namely drivers/gpu/drm/gma500/psb_intel_lvds.c)


Revision tags: v3.3-rc2
# ea51e504 31-Jan-2012 Takashi Iwai <tiwai@suse.de>

Merge branch 'fix/asoc' into for-linus


# b20f8662 28-Jan-2012 Florian Tobias Schandinat <FlorianSchandinat@gmx.de>

Merge commit 'v3.3-rc1' into fbdev-next


# 6c02b7b1 27-Jan-2012 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Merge commit 'v3.3-rc1' into stable/for-linus-fixes-3.3

* commit 'v3.3-rc1': (9775 commits)
Linux 3.3-rc1
x86, syscall: Need __ARCH_WANT_SYS_IPC for 32 bits
qnx4: don't leak ->BitMap on late f

Merge commit 'v3.3-rc1' into stable/for-linus-fixes-3.3

* commit 'v3.3-rc1': (9775 commits)
Linux 3.3-rc1
x86, syscall: Need __ARCH_WANT_SYS_IPC for 32 bits
qnx4: don't leak ->BitMap on late failure exits
qnx4: reduce the insane nesting in qnx4_checkroot()
qnx4: di_fname is an array, for crying out loud...
KEYS: Permit key_serial() to be called with a const key pointer
keys: fix user_defined key sparse messages
ima: fix cred sparse warning
uml: fix compile for x86-64
MPILIB: Add a missing ENOMEM check
tpm: fix (ACPI S3) suspend regression
nvme: fix merge error due to change of 'make_request_fn' fn type
xen: using EXPORT_SYMBOL requires including export.h
gpio: tps65910: Use correct offset for gpio initialization
acpi/apei/einj: Add extensions to EINJ from rev 5.0 of acpi spec
intel_idle: Split up and provide per CPU initialization func
ACPI processor: Remove unneeded variable passed by acpi_processor_hotadd_init V2
tg3: Fix single-vector MSI-X code
openvswitch: Fix multipart datapath dumps.
ipv6: fix per device IP snmp counters
...

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# 19c22c34 21-Jan-2012 Mauro Carvalho Chehab <mchehab@redhat.com>

Merge tag 'v3.3-rc1' into staging/for_v3.3

* tag 'v3.3-rc1': (8187 commits)
Linux 3.3-rc1
x86, syscall: Need __ARCH_WANT_SYS_IPC for 32 bits
qnx4: don't leak ->BitMap on late failure exits
q

Merge tag 'v3.3-rc1' into staging/for_v3.3

* tag 'v3.3-rc1': (8187 commits)
Linux 3.3-rc1
x86, syscall: Need __ARCH_WANT_SYS_IPC for 32 bits
qnx4: don't leak ->BitMap on late failure exits
qnx4: reduce the insane nesting in qnx4_checkroot()
qnx4: di_fname is an array, for crying out loud...
KEYS: Permit key_serial() to be called with a const key pointer
keys: fix user_defined key sparse messages
ima: fix cred sparse warning
uml: fix compile for x86-64
MPILIB: Add a missing ENOMEM check
tpm: fix (ACPI S3) suspend regression
nvme: fix merge error due to change of 'make_request_fn' fn type
xen: using EXPORT_SYMBOL requires including export.h
gpio: tps65910: Use correct offset for gpio initialization
acpi/apei/einj: Add extensions to EINJ from rev 5.0 of acpi spec
intel_idle: Split up and provide per CPU initialization func
ACPI processor: Remove unneeded variable passed by acpi_processor_hotadd_init V2
tg3: Fix single-vector MSI-X code
openvswitch: Fix multipart datapath dumps.
ipv6: fix per device IP snmp counters
...

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# eefad7fd 20-Jan-2012 Takashi Iwai <tiwai@suse.de>

Merge branch 'topic/convert-bint' into topic/hda

Merge the conversions to bint module option type.


Revision tags: v3.3-rc1
# 282f445a 19-Jan-2012 H. Peter Anvin <hpa@linux.intel.com>

Merge remote-tracking branch 'linus/master' into x86/urgent


# 0c929238 17-Jan-2012 Paul Mundt <lethal@linux-sh.org>

Merge branch 'sh/platform-updates' into sh-latest


# b3c9dd18 15-Jan-2012 Linus Torvalds <torvalds@linux-foundation.org>

Merge branch 'for-3.3/core' of git://git.kernel.dk/linux-block

* 'for-3.3/core' of git://git.kernel.dk/linux-block: (37 commits)
Revert "block: recursive merge requests"
block: Stop using macro

Merge branch 'for-3.3/core' of git://git.kernel.dk/linux-block

* 'for-3.3/core' of git://git.kernel.dk/linux-block: (37 commits)
Revert "block: recursive merge requests"
block: Stop using macro stubs for the bio data integrity calls
blockdev: convert some macros to static inlines
fs: remove unneeded plug in mpage_readpages()
block: Add BLKROTATIONAL ioctl
block: Introduce blk_set_stacking_limits function
block: remove WARN_ON_ONCE() in exit_io_context()
block: an exiting task should be allowed to create io_context
block: ioc_cgroup_changed() needs to be exported
block: recursive merge requests
block, cfq: fix empty queue crash caused by request merge
block, cfq: move icq creation and rq->elv.icq association to block core
block, cfq: restructure io_cq creation path for io_context interface cleanup
block, cfq: move io_cq exit/release to blk-ioc.c
block, cfq: move icq cache management to block core
block, cfq: move io_cq lookup to blk-ioc.c
block, cfq: move cfqd->icq_list to request_queue and add request->elv.icq
block, cfq: reorganize cfq_io_context into generic and cfq specific parts
block: remove elevator_queue->ops
block: reorder elevator switch sequence
...

Fix up conflicts in:
- block/blk-cgroup.c
Switch from can_attach_task to can_attach
- block/cfq-iosched.c
conflict with now removed cic index changes (we now use q->id instead)

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Revision tags: v3.2
# c98b2cc2 27-Dec-2011 Tejun Heo <tj@kernel.org>

block: remove WARN_ON_ONCE() in exit_io_context()

6e736be7 "block: make ioc get/put interface more conventional and fix
race on alloction" added WARN_ON_ONCE() in exit_io_context() which
triggers if

block: remove WARN_ON_ONCE() in exit_io_context()

6e736be7 "block: make ioc get/put interface more conventional and fix
race on alloction" added WARN_ON_ONCE() in exit_io_context() which
triggers if !PF_EXITING. All tasks hitting exit_io_context() from
task exit should have PF_EXITING set but task struct tearing down
after fork failure calls into the function without PF_EXITING,
triggering the condition.

WARNING: at block/blk-ioc.c:234 exit_io_context+0x40/0x92()
Pid: 17090, comm: trinity Not tainted 3.2.0-rc6-next-20111222-sasha-dirty #77
Call Trace:
[<ffffffff810b69a3>] warn_slowpath_common+0x8f/0xb2
[<ffffffff810b6a77>] warn_slowpath_null+0x18/0x1a
[<ffffffff8181a7a2>] exit_io_context+0x40/0x92
[<ffffffff810b58c9>] copy_process+0x126f/0x1453
[<ffffffff810b5c1b>] do_fork+0x120/0x3e9
[<ffffffff8106242f>] sys_clone+0x26/0x28
[<ffffffff82425803>] stub_clone+0x13/0x20
---[ end trace a2e4eb670b375238 ]---

Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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# fd638368 25-Dec-2011 Tejun Heo <tj@kernel.org>

block: an exiting task should be allowed to create io_context

While fixing io_context creation / task exit race condition,
6e736be7f2 "block: make ioc get/put interface more conventional and
fix rac

block: an exiting task should be allowed to create io_context

While fixing io_context creation / task exit race condition,
6e736be7f2 "block: make ioc get/put interface more conventional and
fix race on alloction" also prevented an exiting (%PF_EXITING) task
from creating its own io_context. This is incorrect as exit path may
issue IOs, e.g. from exit_files(), and if those IOs are the first ones
issued by the task, io_context needs to be created to process the IOs.

Combined with the existing problem of io_context / io_cq creation
failure having the possibility of stalling IO, this problem results in
deterministic full IO lockup with certain workloads.

Fix it by allowing io_context creation regardless of %PF_EXITING for
%current.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Revision tags: v3.2-rc7
# 64c42998 19-Dec-2011 Jens Axboe <axboe@kernel.dk>

block: ioc_cgroup_changed() needs to be exported

With the ioc changed, ioc_cgroup_changed() can be used by modular
code. So ensure that it is exported.

Reported-by: Stephen Rothwell <sfr@canb.auug.

block: ioc_cgroup_changed() needs to be exported

With the ioc changed, ioc_cgroup_changed() can be used by modular
code. So ensure that it is exported.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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Revision tags: v3.2-rc6
# f1f8cc94 13-Dec-2011 Tejun Heo <tj@kernel.org>

block, cfq: move icq creation and rq->elv.icq association to block core

Now block layer knows everything necessary to create and associate
icq's with requests. Move ioc_create_icq() to blk-ioc.c an

block, cfq: move icq creation and rq->elv.icq association to block core

Now block layer knows everything necessary to create and associate
icq's with requests. Move ioc_create_icq() to blk-ioc.c and update
get_request() such that, if elevator_type->icq_size is set, requests
are automatically associated with their matching icq's before
elv_set_request(). io_context reference is also managed by block core
on request alloc/free.

* Only ioprio/cgroup changed handling remains from cfq_get_cic().
Collapsed into cfq_set_request().

* This removes queue kicking on icq allocation failure (for now). As
icq allocation failure is rare and the only effect of queue kicking
achieved was possibily accelerating queue processing, this change
shouldn't be noticeable.

There is a larger underlying problem. Unlike request allocation,
icq allocation is not guaranteed to succeed eventually after
retries. The number of icq is unbound and thus mempool can't be the
solution either. This effectively adds allocation dependency on
memory free path and thus possibility of deadlock.

This usually wouldn't happen because icq allocation is not a hot
path and, even when the condition triggers, it's highly unlikely
that none of the writeback workers already has icq.

However, this is still possible especially if elevator is being
switched under high memory pressure, so we better get it fixed.
Probably the only solution is just bypassing elevator and appending
to dispatch queue on any elevator allocation failure.

* Comment added to explain how icq's are managed and synchronized.

This completes cleanup of io_context interface.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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# 7e5a8794 13-Dec-2011 Tejun Heo <tj@kernel.org>

block, cfq: move io_cq exit/release to blk-ioc.c

With kmem_cache managed by blk-ioc, io_cq exit/release can be moved to
blk-ioc too. The odd ->io_cq->exit/release() callbacks are replaced
with elev

block, cfq: move io_cq exit/release to blk-ioc.c

With kmem_cache managed by blk-ioc, io_cq exit/release can be moved to
blk-ioc too. The odd ->io_cq->exit/release() callbacks are replaced
with elevator_ops->elevator_exit_icq_fn() with unlinking from both ioc
and q, and freeing automatically handled by blk-ioc. The elevator
operation only need to perform exit operation specific to the elevator
- in cfq's case, exiting the cfqq's.

Also, clearing of io_cq's on q detach is moved to block core and
automatically performed on elevator switch and q release.

Because the q io_cq points to might be freed before RCU callback for
the io_cq runs, blk-ioc code should remember to which cache the io_cq
needs to be freed when the io_cq is released. New field
io_cq->__rcu_icq_cache is added for this purpose. As both the new
field and rcu_head are used only after io_cq is released and the
q/ioc_node fields aren't, they are put into unions.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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# 47fdd4ca 13-Dec-2011 Tejun Heo <tj@kernel.org>

block, cfq: move io_cq lookup to blk-ioc.c

Now that all io_cq related data structures are in block core layer,
io_cq lookup can be moved from cfq-iosched.c to blk-ioc.c.

Lookup logic from cfq_cic_l

block, cfq: move io_cq lookup to blk-ioc.c

Now that all io_cq related data structures are in block core layer,
io_cq lookup can be moved from cfq-iosched.c to blk-ioc.c.

Lookup logic from cfq_cic_lookup() is moved to ioc_lookup_icq() with
parameter return type changes (cfqd -> request_queue, cfq_io_cq ->
io_cq) and cfq_cic_lookup() becomes thin wrapper around
cfq_cic_lookup().

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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# c5869807 13-Dec-2011 Tejun Heo <tj@kernel.org>

block, cfq: reorganize cfq_io_context into generic and cfq specific parts

Currently io_context and cfq logics are mixed without clear boundary.
Most of io_context is independent from cfq but cfq_io_

block, cfq: reorganize cfq_io_context into generic and cfq specific parts

Currently io_context and cfq logics are mixed without clear boundary.
Most of io_context is independent from cfq but cfq_io_context handling
logic is dispersed between generic ioc code and cfq.

cfq_io_context represents association between an io_context and a
request_queue, which is a concept useful outside of cfq, but it also
contains fields which are useful only to cfq.

This patch takes out generic part and put it into io_cq (io
context-queue) and the rest into cfq_io_cq (cic moniker remains the
same) which contains io_cq. The following changes are made together.

* cfq_ttime and cfq_io_cq now live in cfq-iosched.c.

* All related fields, functions and constants are renamed accordingly.

* ioc->ioc_data is now "struct io_cq *" instead of "void *" and
renamed to icq_hint.

This prepares for io_context API cleanup. Documentation is currently
sparse. It will be added later.

Changes in this patch are mechanical and don't cause functional
change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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# f2dbd76a 13-Dec-2011 Tejun Heo <tj@kernel.org>

block, cfq: replace current_io_context() with create_io_context()

When called under queue_lock, current_io_context() triggers lockdep
warning if it hits allocation path. This is because io_context

block, cfq: replace current_io_context() with create_io_context()

When called under queue_lock, current_io_context() triggers lockdep
warning if it hits allocation path. This is because io_context
installation is protected by task_lock which is not IRQ safe, so it
triggers irq-unsafe-lock -> irq -> irq-safe-lock -> irq-unsafe-lock
deadlock warning.

Given the restriction, accessor + creator rolled into one doesn't work
too well. Drop current_io_context() and let the users access
task->io_context directly inside queue_lock combined with explicit
creation using create_io_context().

Future ioc updates will further consolidate ioc access and the create
interface will be unexported.

While at it, relocate ioc internal interface declarations in blk.h and
add section comments before and after.

This patch does not introduce functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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# b2efa052 13-Dec-2011 Tejun Heo <tj@kernel.org>

block, cfq: unlink cfq_io_context's immediately

cic is association between io_context and request_queue. A cic is
linked from both ioc and q and should be destroyed when either one
goes away. As i

block, cfq: unlink cfq_io_context's immediately

cic is association between io_context and request_queue. A cic is
linked from both ioc and q and should be destroyed when either one
goes away. As ioc and q both have their own locks, locking becomes a
bit complex - both orders work for removal from one but not from the
other.

Currently, cfq tries to circumvent this locking order issue with RCU.
ioc->lock nests inside queue_lock but the radix tree and cic's are
also protected by RCU allowing either side to walk their lists without
grabbing lock.

This rather unconventional use of RCU quickly devolves into extremely
fragile convolution. e.g. The following is from cfqd going away too
soon after ioc and q exits raced.

general protection fault: 0000 [#1] PREEMPT SMP
CPU 2
Modules linked in:
[ 88.503444]
Pid: 599, comm: hexdump Not tainted 3.1.0-rc10-work+ #158 Bochs Bochs
RIP: 0010:[<ffffffff81397628>] [<ffffffff81397628>] cfq_exit_single_io_context+0x58/0xf0
...
Call Trace:
[<ffffffff81395a4a>] call_for_each_cic+0x5a/0x90
[<ffffffff81395ab5>] cfq_exit_io_context+0x15/0x20
[<ffffffff81389130>] exit_io_context+0x100/0x140
[<ffffffff81098a29>] do_exit+0x579/0x850
[<ffffffff81098d5b>] do_group_exit+0x5b/0xd0
[<ffffffff81098de7>] sys_exit_group+0x17/0x20
[<ffffffff81b02f2b>] system_call_fastpath+0x16/0x1b

The only real hot path here is cic lookup during request
initialization and avoiding extra locking requires very confined use
of RCU. This patch makes cic removal from both ioc and request_queue
perform double-locking and unlink immediately.

* From q side, the change is almost trivial as ioc->lock nests inside
queue_lock. It just needs to grab each ioc->lock as it walks
cic_list and unlink it.

* From ioc side, it's a bit more difficult because of inversed lock
order. ioc needs its lock to walk its cic_list but can't grab the
matching queue_lock and needs to perform unlock-relock dancing.

Unlinking is now wholly done from put_io_context() and fast path is
optimized by using the queue_lock the caller already holds, which is
by far the most common case. If the ioc accessed multiple devices,
it tries with trylock. In unlikely cases of fast path failure, it
falls back to full double-locking dance from workqueue.

Double-locking isn't the prettiest thing in the world but it's *far*
simpler and more understandable than RCU trick without adding any
meaningful overhead.

This still leaves a lot of now unnecessary RCU logics. Future patches
will trim them.

-v2: Vivek pointed out that cic->q was being dereferenced after
cic->release() was called. Updated to use local variable @this_q
instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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# dc86900e 13-Dec-2011 Tejun Heo <tj@kernel.org>

block, cfq: move ioc ioprio/cgroup changed handling to cic

ioprio/cgroup change was handled by marking the changed state in ioc
and, on the following access to the ioc, performing RCU-protected
iter

block, cfq: move ioc ioprio/cgroup changed handling to cic

ioprio/cgroup change was handled by marking the changed state in ioc
and, on the following access to the ioc, performing RCU-protected
iteration through all cic's grabbing the matching queue_lock.

This patch moves the changed state to each cic. When ioprio or cgroup
changes, the respective bit is set on all cic's of the ioc and when
each of those cic (not ioc) is accessed, change is applied for that
specific ioc-queue pair.

This also fixes the following two race conditions between setting and
clearing of changed states.

* Missing barrier between assign/load of ioprio and ioprio_changed
allowed applying old ioprio.

* Change requests could happen between application of change and
clearing of changed variables.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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# 6e736be7 13-Dec-2011 Tejun Heo <tj@kernel.org>

block: make ioc get/put interface more conventional and fix race on alloction

Ignoring copy_io() during fork, io_context can be allocated from two
places - current_io_context() and set_task_ioprio()

block: make ioc get/put interface more conventional and fix race on alloction

Ignoring copy_io() during fork, io_context can be allocated from two
places - current_io_context() and set_task_ioprio(). The former is
always called from local task while the latter can be called from
different task. The synchornization between them are peculiar and
dubious.

* current_io_context() doesn't grab task_lock() and assumes that if it
saw %NULL ->io_context, it would stay that way until allocation and
assignment is complete. It has smp_wmb() between alloc/init and
assignment.

* set_task_ioprio() grabs task_lock() for assignment and does
smp_read_barrier_depends() between "ioc = task->io_context" and "if
(ioc)". Unfortunately, this doesn't achieve anything - the latter
is not a dependent load of the former. ie, if ioc itself were being
dereferenced "ioc->xxx", it would mean something (not sure what tho)
but as the code currently stands, the dependent read barrier is
noop.

As only one of the the two test-assignment sequences is task_lock()
protected, the task_lock() can't do much about race between the two.
Nothing prevents current_io_context() and set_task_ioprio() allocating
its own ioc for the same task and overwriting the other's.

Also, set_task_ioprio() can race with exiting task and create a new
ioc after exit_io_context() is finished.

ioc get/put doesn't have any reason to be complex. The only hot path
is accessing the existing ioc of %current, which is simple to achieve
given that ->io_context is never destroyed as long as the task is
alive. All other paths can happily go through task_lock() like all
other task sub structures without impacting anything.

This patch updates ioc get/put so that it becomes more conventional.

* alloc_io_context() is replaced with get_task_io_context(). This is
the only interface which can acquire access to ioc of another task.
On return, the caller has an explicit reference to the object which
should be put using put_io_context() afterwards.

* The functionality of current_io_context() remains the same but when
creating a new ioc, it shares the code path with
get_task_io_context() and always goes through task_lock().

* get_io_context() now means incrementing ref on an ioc which the
caller already has access to (be that an explicit refcnt or implicit
%current one).

* PF_EXITING inhibits creation of new io_context and once
exit_io_context() is finished, it's guaranteed that both ioc
acquisition functions return %NULL.

* All users are updated. Most are trivial but
smp_read_barrier_depends() removal from cfq_get_io_context() needs a
bit of explanation. I suppose the original intention was to ensure
ioc->ioprio is visible when set_task_ioprio() allocates new
io_context and installs it; however, this wouldn't have worked
because set_task_ioprio() doesn't have wmb between init and install.
There are other problems with this which will be fixed in another
patch.

* While at it, use NUMA_NO_NODE instead of -1 for wildcard node
specification.

-v2: Vivek spotted contamination from debug patch. Removed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

show more ...


# 42ec57a8 13-Dec-2011 Tejun Heo <tj@kernel.org>

block: misc ioc cleanups

* int return from put_io_context() wasn't used by anybody. Make it
return void like other put functions and docbook-fy the function
comment.

* Reorder dummy declaratio

block: misc ioc cleanups

* int return from put_io_context() wasn't used by anybody. Make it
return void like other put functions and docbook-fy the function
comment.

* Reorder dummy declarations for !CONFIG_BLOCK case a bit.

* Make alloc_ioc_context() use __GFP_ZERO allocation, take init out of
if block and drop 0'ing.

* Docbook-fy current_io_context() comment.

This patch doesn't introduce any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

show more ...


Revision tags: v3.2-rc5, v3.2-rc4
# d4bbf7e7 28-Nov-2011 Tejun Heo <tj@kernel.org>

Merge branch 'master' into x86/memblock

Conflicts & resolutions:

* arch/x86/xen/setup.c

dc91c728fd "xen: allow extra memory to be in multiple regions"
24aa07882b "memblock, x86: Replace memblock

Merge branch 'master' into x86/memblock

Conflicts & resolutions:

* arch/x86/xen/setup.c

dc91c728fd "xen: allow extra memory to be in multiple regions"
24aa07882b "memblock, x86: Replace memblock_x86_reserve/free..."

conflicted on xen_add_extra_mem() updates. The resolution is
trivial as the latter just want to replace
memblock_x86_reserve_range() with memblock_reserve().

* drivers/pci/intel-iommu.c

166e9278a3f "x86/ia64: intel-iommu: move to drivers/iommu/"
5dfe8660a3d "bootmem: Replace work_with_active_regions() with..."

conflicted as the former moved the file under drivers/iommu/.
Resolved by applying the chnages from the latter on the moved
file.

* mm/Kconfig

6661672053a "memblock: add NO_BOOTMEM config symbol"
c378ddd53f9 "memblock, x86: Make ARCH_DISCARD_MEMBLOCK a config option"

conflicted trivially. Both added config options. Just
letting both add their own options resolves the conflict.

* mm/memblock.c

d1f0ece6cdc "mm/memblock.c: small function definition fixes"
ed7b56a799c "memblock: Remove memblock_memory_can_coalesce()"

confliected. The former updates function removed by the
latter. Resolution is trivial.

Signed-off-by: Tejun Heo <tj@kernel.org>

show more ...


Revision tags: v3.2-rc3, v3.2-rc2, v3.2-rc1
# 6ad390a2 26-Oct-2011 Dmitry Torokhov <dmitry.torokhov@gmail.com>

Merge branch 'next' into for-linus


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