13 Jan, 2012
1 commit
-
Replace preprocessor macro stubs with real function declarations to
prevent warnings when CONFIG_BLK_DEV_INTEGRITY is disabled.Signed-off-by: Martin K. Petersen
Signed-off-by: Jens Axboe
12 Jan, 2012
2 commits
-
We prefer to program in C rather than preprocessor and it fixes this
warning when CONFIG_BLK_DEV_INTEGRITY is not set:drivers/md/dm-table.c: In function 'dm_table_set_integrity':
drivers/md/dm-table.c:1285:3: warning: statement with no effect [-Wunused-value]Signed-off-by: Stephen Rothwell
Signed-off-by: Jens Axboe -
The block plug in mpage_readpages() duplicates the one in read_pages().
Signed-off-by: Namjae Jeon
Signed-off-by: Amit Sahrawat
Signed-off-by: Andrew Morton
Signed-off-by: Jens Axboe
11 Jan, 2012
2 commits
-
Introduce an ioctl which permits applications to query whether a block
device is rotational.Signed-off-by: Martin K. Petersen
Signed-off-by: Jens Axboe -
Stacking driver queue limits are typically bounded exclusively by the
capabilities of the low level devices, not by the stacking driver
itself.This patch introduces blk_set_stacking_limits() which has more liberal
metrics than the default queue limits function. This allows us to
inherit topology parameters from bottom devices without manually
tweaking the default limits in each driver prior to calling the stacking
function.Since there is now a clear distinction between stacking and low-level
devices, blk_set_default_limits() has been modified to carry the more
conservative values that we used to manually set in
blk_queue_make_request().Signed-off-by: Martin K. Petersen
Acked-by: Mike Snitzer
Signed-off-by: Jens Axboe
28 Dec, 2011
1 commit
-
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:
[] warn_slowpath_common+0x8f/0xb2
[] warn_slowpath_null+0x18/0x1a
[] exit_io_context+0x40/0x92
[] copy_process+0x126f/0x1453
[] do_fork+0x120/0x3e9
[] sys_clone+0x26/0x28
[] stub_clone+0x13/0x20
---[ end trace a2e4eb670b375238 ]---Reported-by: Sasha Levin
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe
25 Dec, 2011
1 commit
-
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
Reported-by: Andrew Morton
Reported-by: Hugh Dickins
Signed-off-by: Jens Axboe
19 Dec, 2011
1 commit
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With the ioc changed, ioc_cgroup_changed() can be used by modular
code. So ensure that it is exported.Reported-by: Stephen Rothwell
Signed-off-by: Jens Axboe
16 Dec, 2011
2 commits
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In my workload, thread 1 accesses a, a+2, ..., thread 2 accesses a+1,
a+3,.... When the requests are flushed to queue, a and a+1 are merged
to (a, a+1), a+2 and a+3 too to (a+2, a+3), but (a, a+1) and (a+2, a+3)
aren't merged.
With recursive merge below, the workload throughput gets improved 20%
and context switch drops 60%.Signed-off-by: Shaohua Li
Signed-off-by: Jens Axboe -
All requests of a queue could be merged to other requests of other queue.
Such queue will not have request in it, but it's in service tree. This
will cause kernel oops.
I encounter a BUG_ON() in cfq_dispatch_request() with next patch, but the
issue should exist without the patch.Signed-off-by: Shaohua Li
Signed-off-by: Jens Axboe
14 Dec, 2011
26 commits
-
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
Signed-off-by: Jens Axboe -
Add elevator_ops->elevator_init_icq_fn() and restructure
cfq_create_cic() and rename it to ioc_create_icq().The new function expects its caller to pass in io_context, uses
elevator_type->icq_cache, handles generic init, calls the new elevator
operation for elevator specific initialization, and returns pointer to
created or looked up icq. This leaves cfq_icq_pool variable without
any user. Removed.This prepares for io_context interface cleanup and doesn't introduce
any functional difference.Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
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
Signed-off-by: Jens Axboe -
Let elevators set ->icq_size and ->icq_align in elevator_type and
elv_register() and elv_unregister() respectively create and destroy
kmem_cache for icq.* elv_register() now can return failure. All callers updated.
* icq caches are automatically named "ELVNAME_io_cq".
* cfq_slab_setup/kill() are collapsed into cfq_init/exit().
* While at it, minor indentation change for iosched_cfq.elevator_name
for consistency.This will help moving icq management to block core. This doesn't
introduce any functional change.Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
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
Signed-off-by: Jens Axboe -
Most of icq management is about to be moved out of cfq into blk-ioc.
This patch prepares for it.* Move cfqd->icq_list to request_queue->icq_list
* Make request explicitly point to icq instead of through elevator
private data. ->elevator_private[3] is replaced with sub struct elv
which contains icq pointer and priv[2]. cfq is updated accordingly.* Meaningless clearing of ->elevator_private[0] removed from
elv_set_request(). At that point in code, the field was guaranteed
to be %NULL anyway.This patch doesn't introduce any functional change.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
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
Signed-off-by: Jens Axboe -
elevator_queue->ops points to the same ops struct ->elevator_type.ops
is pointing to. The only effect of caching it in elevator_queue is
shorter notation - it doesn't save any indirect derefence.Relocate elevator_type->list which used only during module init/exit
to the end of the structure, rename elevator_queue->elevator_type to
->type, and replace elevator_queue->ops with elevator_queue->type.ops.This doesn't introduce any functional difference.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
Elevator switch sequence first attached the new elevator, then tried
registering it (sysfs) and if that failed attached back the old
elevator. However, sysfs registration doesn't require the elevator to
be attached, so there is no reason to do the "detach, attach new,
register, maybe re-attach old" sequence. It can just do "register,
detach, attach".* elevator_init_queue() is updated to set ->elevator_data directly and
return 0 / -errno. This allows elevator_exit() on an unattached
elevator.* __elv_unregister_queue() which was necessary to unregister
unattached q is removed in favor of __elv_register_queue() which can
register unattached q.* elevator_attach() becomes a single assignment and obscures more then
it helps. Dropped.This will help cleaning up io_context handling across elevator switch.
This patch doesn't introduce visible behavior change.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
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
Signed-off-by: Jens Axboe -
Now that lazy paths are removed, cfqd_dead_key() is meaningless and
cic->q can be used whereever cic->key is used. Kill cic->key.Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
Now that cic's are immediately unlinked under both locks, there's no
need to count and drain cic's before module unload. RCU callback
completion is waited with rcu_barrier().While at it, remove residual RCU operations on cic_list.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
Now that all cic's are immediately unlinked from both ioc and queue,
lazy dropping from lookup path and trimming on elevator unregister are
unnecessary. Kill them and remove now unused elevator_ops->trim().This also leaves call_for_each_cic() without any user. Removed.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
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:[] [] cfq_exit_single_io_context+0x58/0xf0
...
Call Trace:
[] call_for_each_cic+0x5a/0x90
[] cfq_exit_io_context+0x15/0x20
[] exit_io_context+0x100/0x140
[] do_exit+0x579/0x850
[] do_group_exit+0x5b/0xd0
[] sys_exit_group+0x17/0x20
[] system_call_fastpath+0x16/0x1bThe 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
Cc: Vivek Goyal
Signed-off-by: Jens Axboe -
* cfq_cic_lookup() may be called without queue_lock and multiple tasks
can execute it simultaneously for the same shared ioc. Nothing
prevents them racing each other and trying to drop the same dead cic
entry multiple times.* smp_wmb() in cfq_exit_cic() doesn't really do anything and nothing
prevents cfq_cic_lookup() seeing stale cic->key. This usually
doesn't blow up because by the time cic is exited, all requests have
been drained and new requests are terminated before going through
elevator. However, it can still be triggered by plug merge path
which doesn't grab queue_lock and thus can't check DEAD state
reliably.This patch updates lookup locking such that,
* Lookup is always performed under queue_lock. This doesn't add any
more locking. The only issue is cfq_allow_merge() which can be
called from plug merge path without holding any lock. For now, this
is worked around by using cic of the request to merge into, which is
guaranteed to have the same ioc. For longer term, I think it would
be best to separate out plug merge method from regular one.* Spurious ioc->lock locking around cic lookup hint assignment
dropped.Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
cfq_get_io_context() would fail if multiple tasks race to insert cic's
for the same association. This patch restructures
cfq_get_io_context() such that slow path insertion race is handled
properly.Note that the restructuring also makes cfq_get_io_context() called
under queue_lock and performs both ioc and cfqd insertions while
holding both ioc and queue locks. This is part of on-going locking
tightening and will be used to simplify synchronization rules.Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
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
Signed-off-by: Jens Axboe -
Make the following changes to prepare for ioc/cic management cleanup.
* Add cic->q so that ioc can determine the associated queue without
querying cfq. This will eventually replace ->key.* Factor out cfq_release_cic() from cic_free_func(). This function
assumes that the caller handled locking.* Rename __cfq_exit_single_io_context() to cfq_exit_cic() and make it
take only @cic.* Restructure cfq_cic_link() for future updates.
This patch doesn't introduce any functional changes.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
* blk_get_queue() is peculiar in that it returns 0 on success and 1 on
failure instead of 0 / -errno or boolean. Update it such that it
returns %true on success and %false on failure.* Make sure the caller checks for the return value.
* Separate out __blk_get_queue() which doesn't check whether @q is
dead and put it in blk.h. This will be used later.This patch doesn't introduce any functional changes.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
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
Cc: Vivek Goyal
Signed-off-by: Jens Axboe -
* 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
Signed-off-by: Jens Axboe -
cfq allocates per-queue id using ida and uses it to index cic radix
tree from io_context. Move it to q->id and allocate on queue init and
free on queue release. This simplifies cfq a bit and will allow for
further improvements of io context life-cycle management.This patch doesn't introduce any functional difference.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
blk_insert_cloned_request(), blk_execute_rq_nowait() and
blk_flush_plug_list() either didn't check whether the queue was dead
or did it without holding queue_lock. Update them so that dead state
is checked while holding queue_lock.AFAICS, this plugs all holes (requeue doesn't matter as the request is
transitioning atomically from in_flight to queued).Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
When trying to drain all requests, blk_drain_queue() checked only
q->rq.count[]; however, this only tracks REQ_ALLOCED requests. This
patch updates blk_drain_queue() such that it looks at all the counters
and queues so that request_queue is actually empty on completion.Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
There are a number of QUEUE_FLAG_DEAD tests. Add blk_queue_dead()
macro and use it.This patch doesn't introduce any functional difference.
Signed-off-by: Tejun Heo
Signed-off-by: Jens Axboe -
The only user left for blk_insert_request() is sx8 and it can be
trivially switched to use blk_execute_rq_nowait() - special requests
aren't included in io stat and sx8 doesn't use block layer tagging.
Switch sx8 and kill blk_insert_requeset().This patch doesn't introduce any functional difference.
Only compile tested.
Signed-off-by: Tejun Heo
Acked-by: Jeff Garzik
Signed-off-by: Jens Axboe
10 Dec, 2011
4 commits
-
* git://git.samba.org/sfrench/cifs-2.6:
cifs: check for NULL last_entry before calling cifs_save_resume_key
cifs: attempt to freeze while looping on a receive attempt
cifs: Fix sparse warning when calling cifs_strtoUCS
CIFS: Add descriptions to the brlock cache functions -
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86, efi: Calling __pa() with an ioremap()ed address is invalid
x86, hpet: Immediately disable HPET timer 1 if rtc irq is masked
x86/intel_mid: Kconfig select fix
x86/intel_mid: Fix the Kconfig for MID selection -
* 'spi/for-3.2' of git://git.pengutronix.de/git/wsa/linux-2.6:
spi/gpio: fix section mismatch warning
spi/fsl-espi: disable CONFIG_SPI_FSL_ESPI=m build
spi/nuc900: Include linux/module.h
spi/ath79: fix compile error due to missing include
