A user reported a regression due to commit
4853abaa (block: fix flush
machinery for stacking drivers with differring flush flags).
Part of the problem is that blk_insert_flush required a
single bio be attached to the request.  In reality, having
no attached bio is also a valid case, as can be observed with
an empty flush.

[1] http://www.redhat.com/archives/dm-devel/2011-September/msg00154.htmlReported-by: NChristophe Saout <christophe@saout.de>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com
Acked-by: NTejun Heo <tj@kernel.org>

Stable note: 3.1
Cc: stable@vger.kernel.org
Signed-off-by: NJens 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: NHannes Reinecke <hare@suse.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The bug is we're not able to remove the device from blkio cgroup's
per-device control files if it gets unplugged.

To reproduce the bug:

  # mount -t cgroup -o blkio xxx /cgroup
  # cd /cgroup
  # echo "8:0 1000" > blkio.throttle.read_bps_device
  # unplug the device
  # cat blkio.throttle.read_bps_device
  8:0	1000
  # echo "8:0 0" > blkio.throttle.read_bps_device
  -bash: echo: write error: No such device

After patching, the device removal will succeed.

Thanks for the comments of Paul, Zefan, and Vivek.
Signed-off-by: NWanlong Gao <gaowanlong@cn.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <paul@paulmenage.org>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

In __blk_complete_request, we check both QUEUE_FLAG_SAME_COMP and req->cpu
to decide whether we should use req->cpu. Actually the user can also
select the complete cpu by either setting BIO_CPU_AFFINE or by calling
bio_set_completion_cpu. Current solution makes these 2 ways don't work
any more. So we'd better just check req->cpu.
Signed-off-by: NTao Ma <boyu.mt@taobao.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

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: NShaohua Li <shli@kernel.org>
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NJens 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: NShaohua Li <shli@kernel.org>
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Commit 5757a6d7 added the QUEUE_FLAG_SAME_FORCE flag, but fails to
clear that flag when the current state is '2' (SAME_COMP + SAME_FORCE)
and the new state is '1' (SAME_COMP).
Acked-by: NDan Williams <dan.j.williams@intel.com>
Reviewed-by: NRoland Dreier <roland@purestorage.com>
Signed-off-by: NEric Seppanen <eric@purestorage.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Add a new REQ_PRIO to let requests preempt others in the cfq I/O schedule,
and lave REQ_META purely for marking requests as metadata in blktrace.

All existing callers of REQ_META except for XFS are updated to also
set REQ_PRIO for now.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NNamhyung Kim <namhyung@gmail.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

We have a kernel build regression since 3.1-rc1, which is about 10%
regression. The kernel source is in an ext3 filesystem.
Alex Shi bisect it to commit:
commit a07405b7
Author: Justin TerAvest <teravest@google.com>
Date:   Sun Jul 10 22:09:19 2011 +0200

    cfq: Remove special treatment for metadata rqs.

Apparently this is caused by lack metadata preemption, where ext3/ext4
do use READ_META. I didn't see a way to fix the issue, so suggest
reverting the patch.

This reverts commit a07405b7.

Reported-by: Alex Shi<alex.shi@intel.com>
Reported-by: Shaohua Li<shaohua.li@intel.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Commit ae1b1539, 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: NJeff Moyer <jmoyer@redhat.com>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

This patch reverts commit 35ae66e0(block: Make rq_affinity = 1
work as expected). The purpose is to avoid an unnecessary IPI.
Let's take an example. My test box has cpu 0-7, one socket. Say request is
added from CPU 1, blk_complete_request() occurs at CPU 7. Without the reverted
patch, softirq will be done at CPU 7. With it, an IPI will be directed to CPU
0, and softirq will be done at CPU 0. In this case, doing softirq at CPU 0 and
CPU 7 have no difference from cache sharing point view and we can avoid an
ipi if doing it in CPU 7.
An immediate concern is this is just like QUEUE_FLAG_SAME_FORCE, but actually
not. blk_complete_request() is running in interrupt handler, and currently
I/O controller doesn't support multiple interrupts (I checked several LSI
cards and AHCI), so only one CPU can run blk_complete_request(). This is
still quite different as QUEUE_FLAG_SAME_FORCE.
Since only one CPU runs softirq, the only difference with below patch is
softirq not always runs at the first CPU of a group.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

blk_insert_flush has the following check:

	/*
	 * If there's data but flush is not necessary, the request can be
	 * processed directly without going through flush machinery.  Queue
	 * for normal execution.
	 */
	if ((policy & REQ_FSEQ_DATA) &&
	    !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
		list_add_tail(&rq->queuelist, &q->queue_head);
		return;
	}

However, blk_flush_policy will not return with policy set to only
REQ_FSEQ_DATA:

static unsigned int blk_flush_policy(unsigned int fflags, struct request *rq)
{
	unsigned int policy = 0;

	if (fflags & REQ_FLUSH) {
		if (rq->cmd_flags & REQ_FLUSH)
			policy |= REQ_FSEQ_PREFLUSH;
		if (blk_rq_sectors(rq))
			policy |= REQ_FSEQ_DATA;
		if (!(fflags & REQ_FUA) && (rq->cmd_flags & REQ_FUA))
			policy |= REQ_FSEQ_POSTFLUSH;
	}
	return policy;
}

Notice that REQ_FSEQ_DATA is only set if REQ_FLUSH is set.  Fix this
mismatch by moving the setting of REQ_FSEQ_DATA outside of the REQ_FLUSH
check.

Tejun notes:

  Hmmm... yes, this can become a correctness issue if (and only if)
  blk_queue_flush() is called to change q->flush_flags while requests
  are in-flight; otherwise, requests wouldn't reach the function at all.
  Also, I think it would be a generally good idea to always set
  FSEQ_DATA if the request has data.

Cheers,
Jeff
Signed-off-by: NJeff Moyer <jmoyer@redhat.com>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Commit 5757a6d7 introduced a new rq_affinity = 2 so as to make
the request completed in the __make_request cpu. But it makes the
old rq_affinity = 1 not work any more. The root cause is that
if the 'cpu' and 'req->cpu' is in the same group and cpu != req->cpu,
ccpu will be the same as group_cpu, so the completion will be
excuted in the 'cpu' not 'group_cpu'.

This patch fix problem by simpling removing group_cpu and the codes
are more explicit now. If ccpu == cpu, we complete in cpu, otherwise
we raise_blk_irq to ccpu.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Roland Dreier <roland@purestorage.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: NTao Ma <boyu.mt@taobao.com>
Reviewed-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

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: NAkinobu Mita <akinobu.mita@gmail.com>
Tested-by: NPer 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: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove the (unsigned long long) cast in diskstats_show() and adjusts the
seq_printf() format string to 'unsigned long'

diskstats_show() uses part_stat_read() to get the stats, which either
accesses the specified field in the struct disk_stats directly (non SMP)
or sums up the per CPU values in a variable of the same type as the field,
so in any case the result will have the same type and range as the
specified field which for all disk_stats entries is unsigned long

Also, for unsigned long ranges the output of %lu should be identical to
the one of %llu, so no change in the actual proc entry contents.
Signed-off-by: NHerbert Poetzl <herbert@13thfloor.at>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Due to conflicts with the moduleh tree in linux-next, we
run into an include file mess. We really need export.h
in that tree, but if we add module.h locally then the
issue is easier to resolve.
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

FQ keeps track of number of groups which are linked on blkcg->blkg_list.
This is useful to avoid races between queue exit and cgroup exit code
paths. So if at the request queue exit time linked group count is not
zero, that means there are some group out there which is yet to be
deleted under rcu read period and queue exit code should wait for
on rcu period.

In my previous patch I forgot to decrease the number of group count.
So in current form, we nr_blkcg_linked_grps is always non-zero and
we will always wait one rcu period (if BLK_CGROUP=y). The side effect
of this is that it can increase boot time. I am surprised, nobody
complained so far.
Signed-off-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

read request is always sync. Using rw_is_sync() to determine
if a bio is sync.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

This moves the FC classes bsg code to the block layer and
makes it a lib so that other classes like iscsi and SAS can use it.

It is helpful because working with the request queue, bios,
creating scatterlists, etc are a pain that the LLD does not
have to worry about with normal IOs and should not have to
worry about for bsg requests.
Signed-off-by: NMike Christie <michaelc@cs.wisc.edu>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

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: NAkinobu Mita <akinobu.mita@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

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: NMing Lei <tom.leiming@gmail.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Some systems benefit from completions always being steered to the strict
requester cpu rather than the looser "per-socket" steering that
blk_cpu_to_group() attempts by default. This is because the first
CPU in the group mask ends up being completely overloaded with work,
while the others (including the original submitter) has power left
to spare.

Allow the strict mode to be set by writing '2' to the sysfs control
file. This is identical to the scheme used for the nomerges file,
where '2' is a more aggressive setting than just being turned on.

echo 2 > /sys/block/<bdev>/queue/rq_affinity

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Roland Dreier <roland@purestorage.com>
Tested-by: NDave Jiang <dave.jiang@intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

A '!' snuck in before the unlikely, rendering it useless.
Reported-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

USB surprise removal of sr is triggering an oops in
scsi_dispatch_command().  What seems to be happening is that USB is
hanging on to a queue reference until the last close of the upper
device, so the crash is caused by surprise remove of a mounted CD
followed by attempted unmount.

The problem is that USB doesn't issue its final commands as part of
the SCSI teardown path, but on last close when the block queue is long
gone.  The long term fix is probably to make sr do the teardown in the
same way as sd (so remove all the lower bits on ejection, but keep the
upper disk alive until last close of user space).  However, the
current oops can be simply fixed by not allowing any commands to be
sent to a dead queue.

Cc: stable@kernel.org
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>

The rcu callback disk_free_ptbl_rcu_cb() just calls a kfree(),
so we use kfree_rcu() instead of the call_rcu(disk_free_ptbl_rcu_cb).
Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

Currently when the last queue of a group has no request, we don't expire
the queue to hope request from the group comes soon, so the group doesn't
miss its share. But if the think time is big, the assumption isn't correct
and we just waste bandwidth. In such case, we don't do idle.

[global]
runtime=30
direct=1

[test1]
cgroup=test1
cgroup_weight=1000
rw=randread
ioengine=libaio
size=500m
runtime=30
directory=/mnt
filename=file1
thinktime=9000

[test2]
cgroup=test2
cgroup_weight=1000
rw=randread
ioengine=libaio
size=500m
runtime=30
directory=/mnt
filename=file2

	patched		base
test1	64k		39k
test2	548k		540k
total	604k		578k

group1 gets much better throughput because it waits less time.

To check if the patch changes behavior of queue without think time. I also
tried to give test1 2ms think time or no think time. The test result is stable.
The thoughput doesn't change with/without the patch.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currently when the last queue of a service tree has no request, we don't
expire the queue to hope request from the service tree comes soon, so the
service tree doesn't miss its share. But if the think time is big, the
assumption isn't correct and we just waste bandwidth. In such case, we
don't do idle.

[global]
runtime=10
direct=1

[test1]
rw=randread
ioengine=libaio
size=500m
directory=/mnt
filename=file1
thinktime=9000

[test2]
rw=read
ioengine=libaio
size=1G
directory=/mnt
filename=file2

	patched		base
test1	41k/s		33k/s
test2	15868k/s	15789k/s
total	15902k/s	15817k/s

A slightly better

To check if the patch changes behavior of queue without think time. I also
tried to give test1 2ms think time or no think time. The test has variation
even without the patch, but the average throughput doesn't change with/without
the patch.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Move the variables to do think time check to a sepatate struct. This is
to prepare adding think time check for service tree and group. No
functional change.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

fs_excl is a poor man's priority inheritance for filesystems to hint to
the block layer that an operation is important. It was never clearly
specified, not widely adopted, and will not prevent starvation in many
cases (like across cgroups).

fs_excl was introduced with the time sliced CFQ IO scheduler, to
indicate when a process held FS exclusive resources and thus needed
a boost.

It doesn't cover all file systems, and it was never fully complete.
Lets kill it.
Signed-off-by: NJustin TerAvest <teravest@google.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

There is no consistency among filesystems from what bios (or requests)
are marked as being metadata. It's interesting to expose this in traces,
but we shouldn't schedule the requests differently based on whether or
not they're marked as being metadata.
Signed-off-by: NJustin TerAvest <teravest@google.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

When I test fio script with big I/O depth, I found the total throughput drops
compared to some relative small I/O depth. The reason is the thread accumulates
big requests in its plug list and causes some delays (surely this depends
on CPU speed).
I thought we'd better have a threshold for requests. When a threshold reaches,
this means there is no request merge and queue lock contention isn't severe
when pushing per-task requests to queue, so the main advantages of blk plug
don't exist. We can force a plug list flush in this case.
With this, my test throughput actually increases and almost equals to small
I/O depth. Another side effect is irq off time decreases in blk_flush_plug_list()
for big I/O depth.
The BLK_MAX_REQUEST_COUNT is choosen arbitarily, but 16 is efficiently to
reduce lock contention to me. But I'm open here, 32 is ok in my test too.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Due to the recently identified overflow in read_capacity_16() it was
possible for max_discard_sectors to be zero but still have discards
enabled on the associated device's queue.

Eliminate the possibility for blkdev_issue_discard to infinitely loop.

Interestingly this issue wasn't identified until a device, whose
discard_granularity was 0 due to read_capacity_16 overflow, was consumed
by blk_stack_limits() to construct limits for a higher-level DM
multipath device.  The multipath device's resulting limits never had the
discard limits stacked because blk_stack_limits() will only do so if
the bottom device's discard_granularity != 0.  This resulted in the
multipath device's limits.max_discard_sectors being 0.
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

On Linux x86_64 host with 32bit userspace, running
qemu or even just "qemu-img create -f qcow2 some.img 1G"
causes a kernel warning:

ioctl32(qemu-img:5296): Unknown cmd fd(3) cmd(00005326){t:'S';sz:0} arg(7fffffff) on some.img
ioctl32(qemu-img:5296): Unknown cmd fd(3) cmd(801c0204){t:02;sz:28} arg(fff77350) on some.img

ioctl 00005326 is CDROM_DRIVE_STATUS,
ioctl 801c0204 is FDGETPRM.

The warning appears because the Linux compat-ioctl handler for these
ioctls only applies to block devices, while qemu also uses the ioctls on
plain files.
Signed-off-by: NJohannes Stezenbach <js@sig21.net>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Currently, only open(2) is defined as the 'clearing' point.  It has
two roles - first, it's an acknowledgement from userland indicating
that the event has been received and kernel can clear pending states
and proceed to generate more events.  Secondly, it's passed on to
device drivers as a hint indicating that a synchronization point has
been reached and it might want to take a deeper look at the device.

The latter currently is only used by sr which uses two different
mechanisms - GET_EVENT_MEDIA_STATUS_NOTIFICATION and TEST_UNIT_READY
to discover events, where the former is lighter weight and safe to be
used repeatedly but may not provide full coverage.  Among other
things, GET_EVENT can't detect media removal while TUR can.

This patch makes close(2) - blkdev_put() - indicate clearing hint for
MEDIA_CHANGE to drivers.  disk_check_events() is renamed to
disk_flush_events() and updated to take @mask for events to flush
which is or'd to ev->clearing and will be passed to the driver on the
next ->check_events() invocation.

This change makes sr generate MEDIA_CHANGE when media is ejected from
userland - e.g. with eject(1).

Note: Given the current usage, it seems @clearing hint is needlessly
complex.  disk_clear_events() can simply clear all events and the hint
can be boolean @flush.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

ioc->ioc_data is rcu protectd, so uses correct API to access it.
This doesn't change any behavior, but just make code consistent.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Cc: stable@kernel.org # after ab4bd22dSigned-off-by: NJens Axboe <jaxboe@fusionio.com>

I got a rcu warnning at boot. the ioc->ioc_data is rcu_deferenced, but
doesn't hold rcu_read_lock.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Cc: stable@kernel.org # after ab4bd22dSigned-off-by: NJens Axboe <jaxboe@fusionio.com>

copy_from/to_user() and blk_rq_map_user() want __user pointer.
This patch fixes following warnings from sparse:

   CHECK   block/bsg.c
 block/bsg.c:185:38: warning: incorrect type in argument 2 (different address spaces)
 block/bsg.c:185:38:    expected void const [noderef] <asn:1>*from
 block/bsg.c:185:38:    got void *<noident>
 block/bsg.c:295:58: warning: incorrect type in argument 4 (different address spaces)
 block/bsg.c:295:58:    expected void [noderef] <asn:1>*<noident>
 block/bsg.c:295:58:    got void *[assigned] dxferp
 block/bsg.c:311:52: warning: incorrect type in argument 4 (different address spaces)
 block/bsg.c:311:52:    expected void [noderef] <asn:1>*<noident>
 block/bsg.c:311:52:    got void *[assigned] dxferp
 block/bsg.c:448:37: warning: incorrect type in argument 1 (different address spaces)
 block/bsg.c:448:37:    expected void [noderef] <asn:1>*dst
 block/bsg.c:448:37:    got void *<noident>
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Acked-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

Second condition in OR always implies first condition is false
thus bytes_read in the second is not needed. The same goes to
bytes_written.
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Acked-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

POLLOUT should be returned only if bd->queued_cmds < bd->max_queue
so that bsg_alloc_command() can proceed.
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Acked-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

The total of two unsigned values should also be unsigned.

Update throtl_log output to unsigned.
Update total_nr_queued test to non-zero to be the
same as the other total_nr_queued tests.
Signed-off-by: NJoe Perches <joe@perches.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>