Now that we have rq_qos_wait() in place, convert wbt_wait() over to
using it with it's specific callbacks.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Originally when I split out the common code from blk-wbt into rq_qos I
left the wbt_wait() where it was and simply copied and modified it
slightly to work for io-latency. However they are both basically the
same thing, and as time has gone on wbt_wait() has ended up much smarter
and kinder than it was when I copied it into io-latency, which means
io-latency has lost out on these improvements.
Since they are the same thing essentially except for a few minor things,
create rq_qos_wait() that replicates what wbt_wait() currently does with
callbacks that can be passed in for the snowflakes to do their own thing
as appropriate.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blkg reference counting now uses percpu_ref rather than atomic_t. Let's
make this consistent with css_tryget. This renames blkg_try_get to
blkg_tryget and now returns a bool rather than the blkg or %NULL.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Every bio is now associated with a blkg putting blkg_get, blkg_try_get,
and blkg_put on the hot path. Switch over the refcnt in blkg to use
percpu_ref.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that a bio only holds a blkg reference, so clean up is simply
putting back that reference. Remove bio_disassociate_task() as it just
calls bio_disassociate_blkg() and call the latter directly.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The previous patch in this series removed carrying around a pointer to
the css in blkg. However, the blkg association logic still relied on
taking a reference on the css to ensure we wouldn't fail in getting a
reference for the blkg.
Here the implicit dependency on the css is removed. The association
continues to rely on the tryget logic walking up the blkg tree. This
streamlines the three ways that association can happen: normal, swap,
and writeback.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Prior patches ensured that any bio that interacts with a request_queue
is properly associated with a blkg. This makes bio->bi_css unnecessary
as blkg maintains a reference to blkcg already.
This removes the bio field bi_css and transfers corresponding uses to
access via bi_blkg.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
One of the goals of this series is to remove a separate reference to
the css of the bio. This can and should be accessed via bio_blkcg(). In
this patch, wbc_init_bio() now requires a bio to have a device
associated with it.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
A prior patch in this series added blkg association to bios issued by
cgroups. There are two other paths that we want to attribute work back
to the appropriate cgroup: swap and writeback. Here we modify the way
swap tags bios to include the blkg. Writeback will be tackle in the next
patch.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bio_issue_init among other things initializes the timestamp for an IO.
Rather than have this logic handled by policies, this consolidates it to
be on the init paths (normal, clone, bounce clone).
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Previously, blkg association was handled by controller specific code in
blk-throttle and blk-iolatency. However, because a blkg represents a
relationship between a blkcg and a request_queue, it makes sense to keep
the blkg->q and bio->bi_disk->queue consistent.
This patch moves association into the bio_set_dev macro(). This should
cover the majority of cases where the device is set/changed keeping the
two pointers consistent. Fallback code is added to
blkcg_bio_issue_check() to catch any missing paths.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The next patch changes the macro bio_set_dev() to associate a bio with a
blkg based on the device set. However, dm creates a static bio to be
used as the basis for cloning empty flush bios on creation. The
bio_set_dev() call in alloc_dev() will cause problems with the next
patch adding association to bio_set_dev() because the call is before the
bdev is associated with a gendisk (bd_disk is %NULL). To get around
this, set the device on the static bio every time and use that to clone
to the other bios.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There are 3 ways blkg association can happen: association with the
current css, with the page css (swap), or from the wbc css (writeback).
This patch handles how association is done for the first case where we
are associating bsaed on the current css. If there is already a blkg
associated, the css will be reused and association will be redone as the
request_queue may have changed.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There are several scenarios where blkg_lookup_create() can fail such as
the blkcg dying, request_queue is dying, or simply being OOM. Most
handle this by simply falling back to the q->root_blkg and calling it a
day.
This patch implements the notion of closest blkg. During
blkg_lookup_create(), if it fails to create, return the closest blkg
found or the q->root_blkg. blkg_try_get_closest() is introduced and used
during association so a bio is always attached to a blkg.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
To know when to create a blkg, the general pattern is to do a
blkg_lookup() and if that fails, lock and do the lookup again, and if
that fails finally create. It doesn't make much sense for everyone who
wants to do creation to write this themselves.
This changes blkg_lookup_create() to do locking and implement this
pattern. The old blkg_lookup_create() is renamed to
__blkg_lookup_create(). If a call site wants to do its own error
handling or already owns the queue lock, they can use
__blkg_lookup_create(). This will be used in upcoming patches.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The bio_blkcg() function turns out to be inconsistent and consequently
dangerous to use. The first part returns a blkcg where a reference is
owned by the bio meaning it does not need to be rcu protected. However,
the third case, the last line, is problematic:
return css_to_blkcg(task_css(current, io_cgrp_id));
This can race against task migration and the cgroup dying. It is also
semantically different as it must be called rcu protected and is
susceptible to failure when trying to get a reference to it.
This patch adds association ahead of calling bio_blkcg() rather than
after. This makes association a required and explicit step along the
code paths for calling bio_blkcg(). In blk-iolatency, association is
moved above the bio_blkcg() call to ensure it will not return %NULL.
BFQ uses the old bio_blkcg() function, but I do not want to address it
in this series due to the complexity. I have created a private version
documenting the inconsistency and noting not to use it.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If the user did setup polling in the driver we should not require
another know in the block layer to enable it.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This avoids having to have differnet mq_ops for different setups
with or without poll queues.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This was intended to support users like nvme multipath, but is just
getting in the way and adding another indirect call.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Having another indirect all in the fast path doesn't really help
in our post-spectre world. Also having too many queue type is just
going to create confusion, so I'd rather manage them centrally.
Note that the queue type naming and ordering changes a bit - the
first index now is the default queue for everything not explicitly
marked, the optional ones are read and poll queues.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Merge tag 'v4.20-rc5' into for-4.21/block
Pull in v4.20-rc5, solving a conflict we'll otherwise get in aio.c and
also getting the merge fix that went into mainline that users are
hitting testing for-4.21/block and/or for-next.
* tag 'v4.20-rc5': (664 commits)
Linux 4.20-rc5
PCI: Fix incorrect value returned from pcie_get_speed_cap()
MAINTAINERS: Update linux-mips mailing list address
ocfs2: fix potential use after free
mm/khugepaged: fix the xas_create_range() error path
mm/khugepaged: collapse_shmem() do not crash on Compound
mm/khugepaged: collapse_shmem() without freezing new_page
mm/khugepaged: minor reorderings in collapse_shmem()
mm/khugepaged: collapse_shmem() remember to clear holes
mm/khugepaged: fix crashes due to misaccounted holes
mm/khugepaged: collapse_shmem() stop if punched or truncated
mm/huge_memory: fix lockdep complaint on 32-bit i_size_read()
mm/huge_memory: splitting set mapping+index before unfreeze
mm/huge_memory: rename freeze_page() to unmap_page()
initramfs: clean old path before creating a hardlink
kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc() as notrace
psi: make disabling/enabling easier for vendor kernels
proc: fixup map_files test on arm
debugobjects: avoid recursive calls with kmemleak
userfaultfd: shmem: UFFDIO_COPY: set the page dirty if VM_WRITE is not set
...
We only need the request fields and the end_io time if we have
stats enabled, or if we have a scheduler attached as those may
use it for completion time stats.
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
I ran into a bug where after hibernation due to incompatible
backends, the block driver returned BLK_STS_NOTSUPP, with the
current message it's hard to find out what the command flags
were. Adding req->cmd_flags help make the problem easier to
diagnose.
Reviewed-by: Eduardo Valentin <eduval@amazon.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Balbir Singh <sblbir@amzn.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Even if we have no waiters on any of the sbitmap_queue wait states, we
still have to loop every entry to check. We do this for every IO, so
the cost adds up.
Shift a bit of the cost to the slow path, when we actually have waiters.
Wrap prepare_to_wait_exclusive() and finish_wait(), so we can maintain
an internal count of how many are currently active. Then we can simply
check this count in sbq_wake_ptr() and not have to loop if we don't
have any sleepers.
Convert the two users of sbitmap with waiting, blk-mq-tag and iSCSI.
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If we have that hook, we know the driver handles bd->last == true in
a smart fashion. If it does, even for multiple hardware queues, it's
a good idea to flush batches of requests to the device, if we have
batches of requests from the submitter.
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If we are issuing a list of requests, we know if we're at the last one.
If we fail issuing, ensure that we call ->commits_rqs() to flush any
potential previous requests.
Reviewed-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk-mq passes information to the hardware about any given request being
the last that we will issue in this sequence. The point is that hardware
can defer costly doorbell type writes to the last request. But if we run
into errors issuing a sequence of requests, we may never send the request
with bd->last == true set. For that case, we need a hook that tells the
hardware that nothing else is coming right now.
For failures returned by the drivers ->queue_rq() hook, the driver is
responsible for flushing pending requests, if it uses bd->last to
optimize that part. This works like before, no changes there.
Reviewed-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Only do it if we have requests for multiple queues in the same
plug.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
I recently found some code which called blk_mq_free_map_and_requests()
with a NULL set->tags pointer. I fixed the caller, but it seems like a
good idea to add a NULL check here as well. Now we can call:
blk_mq_free_tag_set(set);
blk_mq_free_tag_set(set);
twice in a row and it's harmless.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Give a interface to adjust io timeout(ms) by device.
Signed-off-by: Weiping Zhang <zhangweiping@didiglobal.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We recently got a stack by syzkaller like this:
BUG: sleeping function called from invalid context at mm/slab.h:361
in_atomic(): 1, irqs_disabled(): 0, pid: 6644, name: blkid
INFO: lockdep is turned off.
CPU: 1 PID: 6644 Comm: blkid Not tainted 4.4.163-514.55.6.9.x86_64+ #76
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
0000000000000000 5ba6a6b879e50c00 ffff8801f6b07b10 ffffffff81cb2194
0000000041b58ab3 ffffffff833c7745 ffffffff81cb2080 5ba6a6b879e50c00
0000000000000000 0000000000000001 0000000000000004 0000000000000000
Call Trace:
<IRQ> [<ffffffff81cb2194>] __dump_stack lib/dump_stack.c:15 [inline]
<IRQ> [<ffffffff81cb2194>] dump_stack+0x114/0x1a0 lib/dump_stack.c:51
[<ffffffff8129a981>] ___might_sleep+0x291/0x490 kernel/sched/core.c:7675
[<ffffffff8129ac33>] __might_sleep+0xb3/0x270 kernel/sched/core.c:7637
[<ffffffff81794c13>] slab_pre_alloc_hook mm/slab.h:361 [inline]
[<ffffffff81794c13>] slab_alloc_node mm/slub.c:2610 [inline]
[<ffffffff81794c13>] slab_alloc mm/slub.c:2692 [inline]
[<ffffffff81794c13>] kmem_cache_alloc_trace+0x2c3/0x5c0 mm/slub.c:2709
[<ffffffff81cbe9a7>] kmalloc include/linux/slab.h:479 [inline]
[<ffffffff81cbe9a7>] kzalloc include/linux/slab.h:623 [inline]
[<ffffffff81cbe9a7>] kobject_uevent_env+0x2c7/0x1150 lib/kobject_uevent.c:227
[<ffffffff81cbf84f>] kobject_uevent+0x1f/0x30 lib/kobject_uevent.c:374
[<ffffffff81cbb5b9>] kobject_cleanup lib/kobject.c:633 [inline]
[<ffffffff81cbb5b9>] kobject_release+0x229/0x440 lib/kobject.c:675
[<ffffffff81cbb0a2>] kref_sub include/linux/kref.h:73 [inline]
[<ffffffff81cbb0a2>] kref_put include/linux/kref.h:98 [inline]
[<ffffffff81cbb0a2>] kobject_put+0x72/0xd0 lib/kobject.c:692
[<ffffffff8216f095>] put_device+0x25/0x30 drivers/base/core.c:1237
[<ffffffff81c4cc34>] delete_partition_rcu_cb+0x1d4/0x2f0 block/partition-generic.c:232
[<ffffffff813c08bc>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
[<ffffffff813c08bc>] rcu_do_batch kernel/rcu/tree.c:2705 [inline]
[<ffffffff813c08bc>] invoke_rcu_callbacks kernel/rcu/tree.c:2973 [inline]
[<ffffffff813c08bc>] __rcu_process_callbacks kernel/rcu/tree.c:2940 [inline]
[<ffffffff813c08bc>] rcu_process_callbacks+0x59c/0x1c70 kernel/rcu/tree.c:2957
[<ffffffff8120f509>] __do_softirq+0x299/0xe20 kernel/softirq.c:273
[<ffffffff81210496>] invoke_softirq kernel/softirq.c:350 [inline]
[<ffffffff81210496>] irq_exit+0x216/0x2c0 kernel/softirq.c:391
[<ffffffff82c2cd7b>] exiting_irq arch/x86/include/asm/apic.h:652 [inline]
[<ffffffff82c2cd7b>] smp_apic_timer_interrupt+0x8b/0xc0 arch/x86/kernel/apic/apic.c:926
[<ffffffff82c2bc25>] apic_timer_interrupt+0xa5/0xb0 arch/x86/entry/entry_64.S:746
<EOI> [<ffffffff814cbf40>] ? audit_kill_trees+0x180/0x180
[<ffffffff8187d2f7>] fd_install+0x57/0x80 fs/file.c:626
[<ffffffff8180989e>] do_sys_open+0x45e/0x550 fs/open.c:1043
[<ffffffff818099c2>] SYSC_open fs/open.c:1055 [inline]
[<ffffffff818099c2>] SyS_open+0x32/0x40 fs/open.c:1050
[<ffffffff82c299e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
In softirq context, we call rcu callback function delete_partition_rcu_cb(),
which may allocate memory by kzalloc with GFP_KERNEL flag. If the
allocation cannot be satisfied, it may sleep. However, That is not allowed
in softirq contex.
Although we found this problem on linux 4.4, the latest kernel version
seems to have this problem as well. And it is very similar to the
previous one:
https://lkml.org/lkml/2018/7/9/391
Fix it by using RCU workqueue, which allows sleep.
Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If we yank a 'same_queue_rq' request off the plug list, we should
also decrement the cached request count.
Fixes: 5f0ed774ed ("block: sum requests in the plug structure")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This isn't exactly the same as the previous count, as it includes
requests for all devices. But that really doesn't matter, if we have
more than the threshold (16) queued up, flush it. It's not worth it
to have an expensive list loop for this.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There are no more users relying on blk-mq request states to prevent
double completions, so replace the relatively expensive cmpxchg operation
with WRITE_ONCE.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
A driver may have internal state to cleanup if we're pretending a request
didn't complete. Return 'false' if the command wasn't actually completed
due to the timeout error injection, and true otherwise.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
It's pointless to do so, we are by definition on the CPU we want/need
to be, as that's the one waiting for a completion event.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Right now we immediately bail if need_resched() is true, but
we need to do at least one loop in case we have entries waiting.
So just invert the need_resched() check, putting it at the
bottom of the loop.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_poll() has always kept spinning until it found an IO. This is
fine for SYNC polling, since we need to find one request we have
pending, but in preparation for ASYNC polling it can be beneficial
to just check if we have any entries available or not.
Existing callers are converted to pass in 'spin == true', to retain
the old behavior.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We always pass in -1 now and none of the callers use the tag value,
remove the parameter.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If we want to support async IO polling, then we have to allow finding
completions that aren't just for the one we are looking for. Always pass
in -1 to the mq_ops->poll() helper, and have that return how many events
were found in this poll loop.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Even though .mq_kobj, ctx->kobj and q->kobj share same lifetime
from block layer's view, actually they don't because userspace may
grab one kobject anytime via sysfs.
This patch fixes the issue by the following approach:
1) introduce 'struct blk_mq_ctxs' for holding .mq_kobj and managing
all ctxs
2) free all allocated ctxs and the 'blk_mq_ctxs' instance in release
handler of .mq_kobj
3) grab one ref of .mq_kobj before initializing each ctx->kobj, so that
.mq_kobj is always released after all ctxs are freed.
This patch fixes kernel panic issue during booting when DEBUG_KOBJECT_RELEASE
is enabled.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Cc: "jianchao.wang" <jianchao.w.wang@oracle.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If the first request allocated and issued by a process is a passhthrough
request, we don't set up an IO context for it. Ensure that
blk_mq_sched_assign_ioc() ignores a NULL io_context.
Fixes: e2b3fa5af7 ("block: Remove bio->bi_ioc")
Reported-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For the synchronous I/O path case (read(), write() etc system calls), a
BIO I/O priority is not initialized until the execution of
blk_init_request_from_bio() when the BIO is submitted and a request
initialized for the BIO execution. This is due to the ki_ioprio field of
the struct kiocb defined on stack being always initialized to
IOPRIO_CLASS_NONE, regardless of the calling process I/O context ioprio
value set with ioprio_set(). This late initialization can result in the
BIO being merged to pending requests even when the I/O priorities
differ.
Fix this by initializing the ki_iopriority field of on stack struct
kiocb using the get_current_ioprio() helper, ensuring that all BIOs
allocated and submitted for the system call execution see the correct
intended I/O priority early. With this, since a BIO I/O priority is
always set to the intended effective value for both the sync and async
path, blk_init_request_from_bio() can be simplified.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Adam Manzanares <adam.manzanares@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Growing in size a high priority request by merging it with a lower
priority BIO or request will increase the request execution time. This
is the opposite result of the desired effect of high I/O priorities,
namely getting low I/O latencies. Prevent merging of requests and BIOs
that have different I/O priorities to fix this.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Define get_current_ioprio() as an inline helper to obtain the caller
I/O priority from its task I/O context. Use this helper in
blk_init_request_from_bio() to set a request ioprio.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
bio->bi_ioc is never set so always NULL. Remove references to it in
bio_disassociate_task() and in rq_ioc() and delete this field from
struct bio. With this change, rq_ioc() always returns
current->io_context without the need for a bio argument. Further
simplify the code and make it more readable by also removing this
helper, which also allows to simplify blk_mq_sched_assign_ioc() by
removing its bio argument.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Adam Manzanares <adam.manzanares@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We currently only really support sync poll, ie poll with 1 IO in flight.
This prepares us for supporting async poll.
Note that the returned value isn't necessarily 100% accurate. If poll
races with IRQ completion, we assume that the fact that the task is now
runnable means we found at least one entry. In reality it could be more
than 1, or not even 1. This is fine, the caller will just need to take
this into account.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For the core poll helper, the task state setting don't need to imply any
atomics, as it's the current task itself that is being modified and
we're not going to sleep.
For IRQ driven, the wakeup path have the necessary barriers to not need
us using the heavy handed version of the task state setting.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Merge tag 'v4.20-rc3' into for-4.21/block
Merge in -rc3 to resolve a few conflicts, but also to get a few
important fixes that have gone into mainline since the block
4.21 branch was forked off (most notably the SCSI queue issue,
which is both a conflict AND needed fix).
Signed-off-by: Jens Axboe <axboe@kernel.dk>
