linux-stable.git/block/blk-core.c, branch linux-3.1.y Linux kernel stable tree block: initialize request_queue's numa node during 2012-01-06T22:16:56+00:00 Mike Snitzer snitzer@redhat.com 2011-11-23T09:59:13+00:00 24b14588aef6226f3bcdf37e78af61cbe9a31fd2 commit 5151412dd4338b273afdb107c3772528e9e67d92 upstream. struct request_queue is allocated with __GFP_ZERO so its "node" field is zero before initialization. This causes an oops if node 0 is offline in the page allocator because its zonelists are not initialized. From Dave Young's dmesg: SRAT: Node 1 PXM 2 0-d0000000 SRAT: Node 1 PXM 2 100000000-330000000 SRAT: Node 0 PXM 1 330000000-630000000 Initmem setup node 1 0000000000000000-000000000affb000 ... Built 1 zonelists in Node order, mobility grouping on. ... BUG: unable to handle kernel paging request at 0000000000001c08 IP: [<ffffffff8111c355>] __alloc_pages_nodemask+0xb5/0x870 and __alloc_pages_nodemask+0xb5 translates to a NULL pointer on zonelist->_zonerefs. The fix is to initialize q->node at the time of allocation so the correct node is passed to the slab allocator later. Since blk_init_allocated_queue_node() is no longer needed, merge it with blk_init_allocated_queue(). [rientjes@google.com: changelog, initializing q->node] Reported-by: Dave Young <dyoung@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: David Rientjes <rientjes@google.com> Tested-by: Dave Young <dyoung@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
commit 5151412dd4338b273afdb107c3772528e9e67d92 upstream.

struct request_queue is allocated with __GFP_ZERO so its "node" field is
zero before initialization.  This causes an oops if node 0 is offline in
the page allocator because its zonelists are not initialized.  From Dave
Young's dmesg:

	SRAT: Node 1 PXM 2 0-d0000000
	SRAT: Node 1 PXM 2 100000000-330000000
	SRAT: Node 0 PXM 1 330000000-630000000
	Initmem setup node 1 0000000000000000-000000000affb000
	...
	Built 1 zonelists in Node order, mobility grouping on.
	...
	BUG: unable to handle kernel paging request at 0000000000001c08
	IP: [<ffffffff8111c355>] __alloc_pages_nodemask+0xb5/0x870

and __alloc_pages_nodemask+0xb5 translates to a NULL pointer on
zonelist->_zonerefs.

The fix is to initialize q->node at the time of allocation so the correct
node is passed to the slab allocator later.

Since blk_init_allocated_queue_node() is no longer needed, merge it with
blk_init_allocated_queue().

[rientjes@google.com: changelog, initializing q->node]
Reported-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Tested-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
blk-flush: move the queue kick into 2011-11-11T17:44:36+00:00 Jeff Moyer jmoyer@redhat.com 2011-10-17T10:57:23+00:00 e94d1d00463f6fdcef956828ff698a2bce3f7a8f commit e67b77c791ca2778198c9e7088f3266ed2da7a55 upstream. A dm-multipath user reported[1] a problem when trying to boot a kernel with commit 4853abaae7e4a2af938115ce9071ef8684fb7af4 (block: fix flush machinery for stacking drivers with differring flush flags) applied. It turns out that an empty flush request can be sent into blk_insert_flush. When the BUG_ON was fixed to allow for this, I/O on the underlying device would stall. The reason is that blk_insert_cloned_request does not kick the queue. In the aforementioned commit, I had added a special case to kick the queue if data was sent down but the queue flags did not require a flush. A better solution is to push the queue kick up into blk_insert_cloned_request. This patch, along with a follow-on which fixes the BUG_ON, fixes the issue reported. [1] http://www.redhat.com/archives/dm-devel/2011-September/msg00154.html Reported-by: Christophe Saout <christophe@saout.de> Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
commit e67b77c791ca2778198c9e7088f3266ed2da7a55 upstream.

A dm-multipath user reported[1] a problem when trying to boot
a kernel with commit 4853abaae7e4a2af938115ce9071ef8684fb7af4
(block: fix flush machinery for stacking drivers with differring
flush flags) applied.  It turns out that an empty flush request
can be sent into blk_insert_flush.  When the BUG_ON was fixed
to allow for this, I/O on the underlying device would stall.  The
reason is that blk_insert_cloned_request does not kick the queue.
In the aforementioned commit, I had added a special case to
kick the queue if data was sent down but the queue flags did
not require a flush.  A better solution is to push the queue
kick up into blk_insert_cloned_request.

This patch, along with a follow-on which fixes the BUG_ON, fixes
the issue reported.

[1] http://www.redhat.com/archives/dm-devel/2011-September/msg00154.html

Reported-by: Christophe Saout <christophe@saout.de>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
block: Free queue resources at blk_release_queue() 2011-09-28T14:07:01+00:00 Hannes Reinecke hare@suse.de 2011-09-28T14:07:01+00:00 777eb1bf15b8532c396821774bf6451e563438f5 A kernel crash is observed when a mounted ext3/ext4 filesystem is physically removed. The problem is that blk_cleanup_queue() frees up some resources eg by calling elevator_exit(), which are not checked for in normal operation. So we should rather move these calls to the destructor function blk_release_queue() as at that point all remaining references are gone. However, in doing so we have to ensure that any externally supplied queue_lock is disconnected as the driver might free up the lock after the call of blk_cleanup_queue(), Signed-off-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> 
A kernel crash is observed when a mounted ext3/ext4 filesystem is
physically removed. The problem is that blk_cleanup_queue() frees up
some resources eg by calling elevator_exit(), which are not checked for
in normal operation. So we should rather move these calls to the
destructor function blk_release_queue() as at that point all remaining
references are gone. However, in doing so we have to ensure that any
externally supplied queue_lock is disconnected as the driver might free
up the lock after the call of blk_cleanup_queue(),

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block: simplify force plug flush code a little bit 2011-08-24T14:04:34+00:00 Shaohua Li shaohua.li@intel.com 2011-08-24T14:04:34+00:00 56ebdaf2fa3c5276be201c5d1aff1490b682ecf2 Cleaning up the code a little bit. attempt_plug_merge() traverses the plug list anyway, we can do the request counting there, so stack size is reduced a little bit. The motivation here is I suspect if we should count the requests for each queue (task could handle multiple disks in the meantime), but my test doesn't show it's worthy doing. If somebody proves we should do it, below change will make that more easier. Signed-off-by: Shaohua Li <shli@kernel.org> Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com> 
Cleaning up the code a little bit. attempt_plug_merge() traverses the plug
list anyway, we can do the request counting there, so stack size is reduced
a little bit.
The motivation here is I suspect if we should count the requests for each
queue (task could handle multiple disks in the meantime), but my test doesn't
show it's worthy doing. If somebody proves we should do it, below change
will make that more easier.

Signed-off-by: Shaohua Li <shli@kernel.org>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
block: change force plug flush call order 2011-08-24T14:04:32+00:00 Shaohua Li shaohua.li@intel.com 2011-08-24T14:04:32+00:00 a63271627521b825b0dd0a564e9a9c62b4c1ca89 Do blk_flush_plug_list() first and then add new request aDo blk_flush_plug_list() first and then add new request aDo blk_flush_plug_list() first and then add new request at the tail. New request can't be merged to existing requests, but later new requests might be merged with this new one. If blk_flush_plug_list() is done later, the merge doesn't happen. Believe it or not, this fixes a 10% regression running sysbench workload. Signed-off-by: Shaohua Li <shli@kernel.org> Signed-off-by: Shaohua Li <shaohua.li@intel.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com> 
Do blk_flush_plug_list() first and then add new request aDo blk_flush_plug_list() first and then add new request aDo blk_flush_plug_list() first and then add new request at the tail. New
request can't be merged to existing requests, but later new requests might
be merged with this new one. If blk_flush_plug_list() is done later, the
merge doesn't happen.
Believe it or not, this fixes a 10% regression running sysbench workload.

Signed-off-by: Shaohua Li <shli@kernel.org>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2011-08-19T17:47:07+00:00 Linus Torvalds torvalds@linux-foundation.org 2011-08-19T17:47:07+00:00 5ccc38740a283aba81a00e92941310d0c1aeb2ee * 'for-linus' of git://git.kernel.dk/linux-block: (23 commits) Revert "cfq: Remove special treatment for metadata rqs." block: fix flush machinery for stacking drivers with differring flush flags block: improve rq_affinity placement blktrace: add FLUSH/FUA support Move some REQ flags to the common bio/request area allow blk_flush_policy to return REQ_FSEQ_DATA independent of *FLUSH xen/blkback: Make description more obvious. cfq-iosched: Add documentation about idling block: Make rq_affinity = 1 work as expected block: swim3: fix unterminated of_device_id table block/genhd.c: remove useless cast in diskstats_show() drivers/cdrom/cdrom.c: relax check on dvd manufacturer value drivers/block/drbd/drbd_nl.c: use bitmap_parse instead of __bitmap_parse bsg-lib: add module.h include cfq-iosched: Reduce linked group count upon group destruction blk-throttle: correctly determine sync bio loop: fix deadlock when sysfs and LOOP_CLR_FD race against each other loop: add BLK_DEV_LOOP_MIN_COUNT=%i to allow distros 0 pre-allocated loop devices loop: add management interface for on-demand device allocation loop: replace linked list of allocated devices with an idr index ... 
* 'for-linus' of git://git.kernel.dk/linux-block: (23 commits)
  Revert "cfq: Remove special treatment for metadata rqs."
  block: fix flush machinery for stacking drivers with differring flush flags
  block: improve rq_affinity placement
  blktrace: add FLUSH/FUA support
  Move some REQ flags to the common bio/request area
  allow blk_flush_policy to return REQ_FSEQ_DATA independent of *FLUSH
  xen/blkback: Make description more obvious.
  cfq-iosched: Add documentation about idling
  block: Make rq_affinity = 1 work as expected
  block: swim3: fix unterminated of_device_id table
  block/genhd.c: remove useless cast in diskstats_show()
  drivers/cdrom/cdrom.c: relax check on dvd manufacturer value
  drivers/block/drbd/drbd_nl.c: use bitmap_parse instead of __bitmap_parse
  bsg-lib: add module.h include
  cfq-iosched: Reduce linked group count upon group destruction
  blk-throttle: correctly determine sync bio
  loop: fix deadlock when sysfs and LOOP_CLR_FD race against each other
  loop: add BLK_DEV_LOOP_MIN_COUNT=%i to allow distros 0 pre-allocated loop devices
  loop: add management interface for on-demand device allocation
  loop: replace linked list of allocated devices with an idr index
  ...
block: fix flush machinery for stacking drivers with differring flush flags 2011-08-15T19:37:25+00:00 Jeff Moyer jmoyer@redhat.com 2011-08-15T19:37:25+00:00 4853abaae7e4a2af938115ce9071ef8684fb7af4 Commit ae1b1539622fb46e51b4d13b3f9e5f4c713f86ae, block: reimplement FLUSH/FUA to support merge, introduced a performance regression when running any sort of fsyncing workload using dm-multipath and certain storage (in our case, an HP EVA). The test I ran was fs_mark, and it dropped from ~800 files/sec on ext4 to ~100 files/sec. It turns out that dm-multipath always advertised flush+fua support, and passed commands on down the stack, where those flags used to get stripped off. The above commit changed that behavior: static inline struct request *__elv_next_request(struct request_queue *q) { struct request *rq; while (1) { - while (!list_empty(&q->queue_head)) { + if (!list_empty(&q->queue_head)) { rq = list_entry_rq(q->queue_head.next); - if (!(rq->cmd_flags & (REQ_FLUSH | REQ_FUA)) || - (rq->cmd_flags & REQ_FLUSH_SEQ)) - return rq; - rq = blk_do_flush(q, rq); - if (rq) - return rq; + return rq; } Note that previously, a command would come in here, have REQ_FLUSH|REQ_FUA set, and then get handed off to blk_do_flush: struct request *blk_do_flush(struct request_queue *q, struct request *rq) { unsigned int fflags = q->flush_flags; /* may change, cache it */ bool has_flush = fflags & REQ_FLUSH, has_fua = fflags & REQ_FUA; bool do_preflush = has_flush && (rq->cmd_flags & REQ_FLUSH); bool do_postflush = has_flush && !has_fua && (rq->cmd_flags & REQ_FUA); unsigned skip = 0; ... if (blk_rq_sectors(rq) && !do_preflush && !do_postflush) { rq->cmd_flags &= ~REQ_FLUSH; if (!has_fua) rq->cmd_flags &= ~REQ_FUA; return rq; } So, the flush machinery was bypassed in such cases (q->flush_flags == 0 && rq->cmd_flags & (REQ_FLUSH|REQ_FUA)). Now, however, we don't get into the flush machinery at all. Instead, __elv_next_request just hands a request with flush and fua bits set to the scsi_request_fn, even if the underlying request_queue does not support flush or fua. The agreed upon approach is to fix the flush machinery to allow stacking. While this isn't used in practice (since there is only one request-based dm target, and that target will now reflect the flush flags of the underlying device), it does future-proof the solution, and make it function as designed. In order to make this work, I had to add a field to the struct request, inside the flush structure (to store the original req->end_io). Shaohua had suggested overloading the union with rb_node and completion_data, but the completion data is used by device mapper and can also be used by other drivers. So, I didn't see a way around the additional field. I tested this patch on an HP EVA with both ext4 and xfs, and it recovers the lost performance. Comments and other testers, as always, are appreciated. Cheers, Jeff Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com> 
Commit ae1b1539622fb46e51b4d13b3f9e5f4c713f86ae, block: reimplement
FLUSH/FUA to support merge, introduced a performance regression when
running any sort of fsyncing workload using dm-multipath and certain
storage (in our case, an HP EVA).  The test I ran was fs_mark, and it
dropped from ~800 files/sec on ext4 to ~100 files/sec.  It turns out
that dm-multipath always advertised flush+fua support, and passed
commands on down the stack, where those flags used to get stripped off.
The above commit changed that behavior:

static inline struct request *__elv_next_request(struct request_queue *q)
{
        struct request *rq;

        while (1) {
-               while (!list_empty(&q->queue_head)) {
+               if (!list_empty(&q->queue_head)) {
                        rq = list_entry_rq(q->queue_head.next);
-                       if (!(rq->cmd_flags & (REQ_FLUSH | REQ_FUA)) ||
-                           (rq->cmd_flags & REQ_FLUSH_SEQ))
-                               return rq;
-                       rq = blk_do_flush(q, rq);
-                       if (rq)
-                               return rq;
+                       return rq;
                }

Note that previously, a command would come in here, have
REQ_FLUSH|REQ_FUA set, and then get handed off to blk_do_flush:

struct request *blk_do_flush(struct request_queue *q, struct request *rq)
{
        unsigned int fflags = q->flush_flags; /* may change, cache it */
        bool has_flush = fflags & REQ_FLUSH, has_fua = fflags & REQ_FUA;
        bool do_preflush = has_flush && (rq->cmd_flags & REQ_FLUSH);
        bool do_postflush = has_flush && !has_fua && (rq->cmd_flags &
        REQ_FUA);
        unsigned skip = 0;
...
        if (blk_rq_sectors(rq) && !do_preflush && !do_postflush) {
                rq->cmd_flags &= ~REQ_FLUSH;
		if (!has_fua)
			rq->cmd_flags &= ~REQ_FUA;
	        return rq;
	}

So, the flush machinery was bypassed in such cases (q->flush_flags == 0
&& rq->cmd_flags & (REQ_FLUSH|REQ_FUA)).

Now, however, we don't get into the flush machinery at all.  Instead,
__elv_next_request just hands a request with flush and fua bits set to
the scsi_request_fn, even if the underlying request_queue does not
support flush or fua.

The agreed upon approach is to fix the flush machinery to allow
stacking.  While this isn't used in practice (since there is only one
request-based dm target, and that target will now reflect the flush
flags of the underlying device), it does future-proof the solution, and
make it function as designed.

In order to make this work, I had to add a field to the struct request,
inside the flush structure (to store the original req->end_io).  Shaohua
had suggested overloading the union with rb_node and completion_data,
but the completion data is used by device mapper and can also be used by
other drivers.  So, I didn't see a way around the additional field.

I tested this patch on an HP EVA with both ext4 and xfs, and it recovers
the lost performance.  Comments and other testers, as always, are
appreciated.

Cheers,
Jeff

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
fault-injection: add ability to export fault_attr in arbitrary directory 2011-08-04T00:25:20+00:00 Akinobu Mita akinobu.mita@gmail.com 2011-08-03T23:21:01+00:00 dd48c085c1cdf9446f92826f1fd451167fb6c2fd init_fault_attr_dentries() is used to export fault_attr via debugfs. But it can only export it in debugfs root directory. Per Forlin is working on mmc_fail_request which adds support to inject data errors after a completed host transfer in MMC subsystem. The fault_attr for mmc_fail_request should be defined per mmc host and export it in debugfs directory per mmc host like /sys/kernel/debug/mmc0/mmc_fail_request. init_fault_attr_dentries() doesn't help for mmc_fail_request. So this introduces fault_create_debugfs_attr() which is able to create a directory in the arbitrary directory and replace init_fault_attr_dentries(). [akpm@linux-foundation.org: extraneous semicolon, per Randy] Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Tested-by: Per Forlin <per.forlin@linaro.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Pekka Enberg <penberg@kernel.org> Cc: Matt Mackall <mpm@selenic.com> Cc: Randy Dunlap <rdunlap@xenotime.net> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
init_fault_attr_dentries() is used to export fault_attr via debugfs.
But it can only export it in debugfs root directory.

Per Forlin is working on mmc_fail_request which adds support to inject
data errors after a completed host transfer in MMC subsystem.

The fault_attr for mmc_fail_request should be defined per mmc host and
export it in debugfs directory per mmc host like
/sys/kernel/debug/mmc0/mmc_fail_request.

init_fault_attr_dentries() doesn't help for mmc_fail_request.  So this
introduces fault_create_debugfs_attr() which is able to create a
directory in the arbitrary directory and replace
init_fault_attr_dentries().

[akpm@linux-foundation.org: extraneous semicolon, per Randy]
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Tested-by: Per Forlin <per.forlin@linaro.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fail_make_request: cleanup should_fail_request 2011-07-26T23:49:46+00:00 Akinobu Mita akinobu.mita@gmail.com 2011-07-26T23:09:03+00:00 b2c9cd3793e5878e301ec2219785a7b8ca402ef1 This changes should_fail_request() to more usable wrapper function of should_fail(). It can avoid putting #ifdef CONFIG_FAIL_MAKE_REQUEST in the middle of a function. Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
This changes should_fail_request() to more usable wrapper function of
should_fail().  It can avoid putting #ifdef CONFIG_FAIL_MAKE_REQUEST in
the middle of a function.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
block: fix warning with calling smp_processor_id() in preemptible section 2011-07-26T13:01:15+00:00 Jens Axboe jaxboe@fusionio.com 2011-07-26T13:01:15+00:00 11ccf116d0d756d06989775288e41f737d98e0c5 After commit 5757a6d7 introduced an unsafe calling of smp_processor_id(), with preempt debuggin turned on we spew a lot of: BUG: using smp_processor_id() in preemptible [00000000] code: kjournald/514 caller is __make_request+0x1b8/0x308 [<c0019f44>] (unwind_backtrace+0x0/0xe8) from [<c024b4cc>] (debug_smp_processor_id+0xbc/0xf0) [<c024b4cc>] (debug_smp_processor_id+0xbc/0xf0) from [<c0223d14>] (__make_request+0x1b8/0x308) [<c0223d14>] (__make_request+0x1b8/0x308) from [<c02215ac>] (generic_make_request+0x4dc/0x558) [<c02215ac>] (generic_make_request+0x4dc/0x558) from [<c022173c>] (submit_bio+0x114/0x138) [<c022173c>] (submit_bio+0x114/0x138) from [<c011f504>] (submit_bh+0x148/0x16c) [<c011f504>] (submit_bh+0x148/0x16c) from [<c0121ed8>] (__sync_dirty_buffer+0x88/0xd8) [<c0121ed8>] (__sync_dirty_buffer+0x88/0xd8) from [<c01aff78>] (journal_commit_transaction+0x1198/0x1688) [<c01aff78>] (journal_commit_transaction+0x1198/0x1688) from [<c01b4034>] (kjournald+0xb4/0x224) [<c01b4034>] (kjournald+0xb4/0x224) from [<c0069ea0>] (kthread+0x8c/0x94) [<c0069ea0>] (kthread+0x8c/0x94) from [<c00137f8>] (kernel_thread_exit+0x0/0x8) Fix this by just using raw_smp_processor_id(), it's just a hint after all. There's no pinning of the CPU or accessing per-cpu structures involved. Reported-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com> 
After commit 5757a6d7 introduced an unsafe calling of
smp_processor_id(), with preempt debuggin turned on we spew a lot of:

BUG: using smp_processor_id() in preemptible [00000000] code: kjournald/514
caller is __make_request+0x1b8/0x308
[<c0019f44>] (unwind_backtrace+0x0/0xe8) from [<c024b4cc>] (debug_smp_processor_id+0xbc/0xf0)
[<c024b4cc>] (debug_smp_processor_id+0xbc/0xf0) from [<c0223d14>] (__make_request+0x1b8/0x308)
[<c0223d14>] (__make_request+0x1b8/0x308) from [<c02215ac>] (generic_make_request+0x4dc/0x558)
[<c02215ac>] (generic_make_request+0x4dc/0x558) from [<c022173c>] (submit_bio+0x114/0x138)
[<c022173c>] (submit_bio+0x114/0x138) from [<c011f504>] (submit_bh+0x148/0x16c)
[<c011f504>] (submit_bh+0x148/0x16c) from [<c0121ed8>] (__sync_dirty_buffer+0x88/0xd8)
[<c0121ed8>] (__sync_dirty_buffer+0x88/0xd8) from [<c01aff78>] (journal_commit_transaction+0x1198/0x1688)
[<c01aff78>] (journal_commit_transaction+0x1198/0x1688) from [<c01b4034>] (kjournald+0xb4/0x224)
[<c01b4034>] (kjournald+0xb4/0x224) from [<c0069ea0>] (kthread+0x8c/0x94)
[<c0069ea0>] (kthread+0x8c/0x94) from [<c00137f8>] (kernel_thread_exit+0x0/0x8)

Fix this by just using raw_smp_processor_id(), it's just a hint
after all. There's no pinning of the CPU or accessing per-cpu
structures involved.

Reported-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>