In case of shared tags and none io sched, batched completion still may
be run into, and hctx->nr_active is accounted when getting driver tag,
so it has to be updated in blk_mq_end_request_batch().
Otherwise, hctx->nr_active may become same with queue depth, then
hctx_may_queue() always return false, then io hang is caused.
Fixes the issue by updating the counter in batched way.
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Fixes: f794f3351f ("block: add support for blk_mq_end_request_batch()")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20211102153619.3627505-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
It's not safe to do this before blk_queue_enter(), as the scheduler state
could have changed in between. Hence move the RQF_ELV setting into the
allocators, where we know the queue is already entered.
Suggested-by: Ming Lei <ming.lei@redhat.com>
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Reported-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
A previous commit fixed up the condition for doing direct issue, but that
left the 'from_schedule' argument dead inside the branch. Replace it with
'false'.
Fixes: ff1552232b ("blk-mq: don't issue request directly in case that current is to be blocked")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Ensure that current tag is correctly assigned before attempting
to prefetch the first cacheline of the request.
Fixes: 92aff191cc ("block: prefetch request to be initialized")
Reported-and-tested-by: syzbot+cd20829ac44b92bf6ed0@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Merge tag 'for-5.16/block-2021-10-29' of git://git.kernel.dk/linux-block
Pull block updates from Jens Axboe:
- mq-deadline accounting improvements (Bart)
- blk-wbt timer fix (Andrea)
- Untangle the block layer includes (Christoph)
- Rework the poll support to be bio based, which will enable adding
support for polling for bio based drivers (Christoph)
- Block layer core support for multi-actuator drives (Damien)
- blk-crypto improvements (Eric)
- Batched tag allocation support (me)
- Request completion batching support (me)
- Plugging improvements (me)
- Shared tag set improvements (John)
- Concurrent queue quiesce support (Ming)
- Cache bdev in ->private_data for block devices (Pavel)
- bdev dio improvements (Pavel)
- Block device invalidation and block size improvements (Xie)
- Various cleanups, fixes, and improvements (Christoph, Jackie,
Masahira, Tejun, Yu, Pavel, Zheng, me)
* tag 'for-5.16/block-2021-10-29' of git://git.kernel.dk/linux-block: (174 commits)
blk-mq-debugfs: Show active requests per queue for shared tags
block: improve readability of blk_mq_end_request_batch()
virtio-blk: Use blk_validate_block_size() to validate block size
loop: Use blk_validate_block_size() to validate block size
nbd: Use blk_validate_block_size() to validate block size
block: Add a helper to validate the block size
block: re-flow blk_mq_rq_ctx_init()
block: prefetch request to be initialized
block: pass in blk_mq_tags to blk_mq_rq_ctx_init()
block: add rq_flags to struct blk_mq_alloc_data
block: add async version of bio_set_polled
block: kill DIO_MULTI_BIO
block: kill unused polling bits in __blkdev_direct_IO()
block: avoid extra iter advance with async iocb
block: Add independent access ranges support
blk-mq: don't issue request directly in case that current is to be blocked
sbitmap: silence data race warning
blk-cgroup: synchronize blkg creation against policy deactivation
block: refactor bio_iov_bvec_set()
block: add single bio async direct IO helper
...
It's faster and easier to read if we tolerate cur_hctx being NULL in
the "when to flush" condition. Rename last_hctx to cur_hctx while at it,
as it better describes the role of that variable.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that we have flags passed in, we can do a final re-arrange of the
flow of blk_mq_rq_ctx_init() so we're always writing request in the
order in which it is laid out.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20211019153300.623322-5-axboe@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now we have the tags available in __blk_mq_alloc_requests_batch(), we
can start fetching the first request cacheline before calling into the
request initialization.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20211019153300.623322-4-axboe@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Instead of getting this from data for every invocation of request
initialization, pass it in as an argument instead.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20211019153300.623322-3-axboe@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There's a hole here we can use, and it's faster to set this earlier
rather than need to check q->elevator multiple times.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20211019153300.623322-2-axboe@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When dispatching a zone append write request to a SCSI zoned block device,
if the target zone of the request is already locked, the device driver will
return BLK_STS_ZONE_RESOURCE and the request will be pushed back to the
hctx dipatch queue. The queue will be marked as RESTART in
dd_finish_request() and restarted in __blk_mq_free_request(). However, this
restart applies to the hctx of the completed request. If the requeued
request is on a different hctx, dispatch will no be retried until another
request is submitted or the next periodic queue run triggers, leading to up
to 30 seconds latency for the requeued request.
Fix this problem by scheduling a queue restart similarly to the
BLK_STS_RESOURCE case or when we cannot get the budget.
Also, consolidate the checks into the "need_resource" variable to simplify
the condition.
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Niklas Cassel <Niklas.Cassel@wdc.com>
Link: https://lore.kernel.org/r/20211026165127.4151055-1-naohiro.aota@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When flushing plug list in case that current will be blocked, we can't
issue request directly because ->queue_rq() may sleep, otherwise scheduler
may complain.
Fixes: dc5fc361d8 ("block: attempt direct issue of plug list")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20211026082257.2889890-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Shinichiro Kawasaki reports that there is a bug in a recent
req_bio_endio() patch causing problems with zonefs. As Shinichiro
suggested, inverse the condition in zone append path to resemble how it
was before: fail when it's not fully completed.
Fixes: 478eb72b81 ("block: optimise req_bio_endio()")
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/344ea4e334aace9148b41af5f2426da38c8aa65a.1634914228.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Replace the call to blk_flush_plug_list in blk_mq_submit_bio with a
direct call to blk_mq_flush_plug_list. This means we do not flush
plug callback from stackable devices, which doesn't really help with
the accumulated requests anyway, and it also means the cached requests
aren't freed here as they can still be used later on.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211020144119.142582-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This check is meant to catch cases where a requeue is attempted on a
request that is still inserted. It's never really been useful to catch any
misuse, and now it's actively wrong. Outside of that, this should not be a
BUG_ON() to begin with.
Remove the check as it's now causing active harm, as requeue off the plug
path will trigger it even though the request state is just fine.
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Link: https://lore.kernel.org/linux-block/CAHj4cs80zAUc2grnCZ015-2Rvd-=gXRfB_dFKy=RTm+wRo09HQ@mail.gmail.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
First, get rid of an extra branch and chain error checks. Also reshuffle
it with bio_advance(), so it goes closer to the final check, with that
the compiler loads rq->rq_flags only once, and also doesn't reload
bio->bi_iter.bi_size if bio_advance() didn't actually advanced the iter.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If we don't use an IO scheduler or have shared tags, then we don't need
to call into this external function at all. This saves ~2% for such
a setup.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Return to the normal blk_mq_submit_bio flow if the bio did not end up
actually being a flush because the device didn't support it. Note that
this is basically impossible to hit without special instrumentation given
that submit_bio_checks already clears these flags usually, so we'd need a
tight race to actually hit this code path.
With this the call to blk_mq_run_hw_queue for the flush requests can be
removed given that the actual flush requests are always issued via the
requeue workqueue which runs the queue unconditionally.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211019122553.2467817-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If we have just one queue type in the plug list, then we can extend our
direct issue to cover a full plug list as well. This allows sending a
batch of requests for direct issue, which is more efficient than doing
one-at-a-time kind of issue.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use a singly linked list for the blk_plug. This saves 8 bytes in the
blk_plug struct, and makes for faster list manipulations than doubly
linked lists. As we don't use the doubly linked lists for anything,
singly linked is just fine.
This yields a bump in default (merging enabled) performance from 7.0
to 7.1M IOPS, and ~7.5M IOPS with merging disabled.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This is in the fast path of driver issue or completion, and it's a single
array index operation. Move it inline to avoid a function call for it.
This does mean making struct blk_mq_tags block layer public, but there's
not really much in there.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Even if we have multiple queues in the plug list, chances that they
are very interspersed is minimal. Don't bother spending CPU cycles
sorting the list.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Instead of returning the same queue request through a request pointer,
use a boolean to accomplish the same.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We only need to call it to resolve the blk_status_t -> errno mapping for
tracing, so move the conversion into the tracepoints that are not called
at all when tracing isn't enabled.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We added RQF_ELV to tell whether there's an IO scheduler attached, and
RQF_ELVPRIV tells us whether there's an IO scheduler with private data
attached. Don't check RQF_ELV in blk_mq_free_request(), what we care
about here is just if we have scheduler private data attached.
This fixes a boot crash
Fixes: 2ff0682da6 ("block: store elevator state in request")
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Reported-by: syzbot+eb8104072aeab6cc1195@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Instead of calling blk_mq_end_request() on a single request, add a helper
that takes the new struct io_comp_batch and completes any request stored
in there.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
struct io_comp_batch contains a list head and a completion handler, which
will allow completions to more effciently completed batches of IO.
For now, no functional changes in this patch, we just define the
io_comp_batch structure and add the argument to the file_operations iopoll
handler.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Instead of open-coding the list additions, traversal, and removal,
provide a basic set of helpers.
Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Just like the blk_mq_ctx counterparts, we've got a bunch of counters
in here that are only for debugfs and are of questionnable value. They
are:
- dispatched, index of how many requests were dispatched in one go
- poll_{considered,invoked,success}, which track poll sucess rates. We're
confident in the iopoll implementation at this point, don't bother
tracking these.
As a bonus, this shrinks each hardware queue from 576 bytes to 512 bytes,
dropping a whole cacheline.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
These were added as part of early days debugging for blk-mq, and they
are not really useful anymore. Rather than spend cycles updating them,
just get rid of them.
As a bonus, this shrinks the per-cpu software queue size from 256b
to 192b. That's a whole cacheline less.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add a local variable for rq_flags, it helps to compile out some of
rq_flags reloads.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We should have enough of registers in blk_mq_rq_ctx_init(), store them
in local vars, so we don't keep reloading them.
note: keeping q->elevator may look unnecessary, but it's also used
inside inlined blk_mq_tags_from_data().
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Don't init rq->hash and rq->rb_node in blk_mq_rq_ctx_init() if there is
no elevator. Also, move some other initialisers that imply barriers to
the end, so the compiler is free to rearrange and optimise other the
rest of them.
note: fold in a change from Jens leaving queue_list unconditional, as
it might lead to problems otherwise.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add an rq private RQF_ELV flag, which tells the block layer that this
request was initialized on a queue that has an IO scheduler attached.
This allows for faster checking in the fast path, rather than having to
deference rq->q later on.
Elevator switching does full quiesce of the queue before detaching an
IO scheduler, so it's safe to cache this in the request itself.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For some reason we still have them in blk-core, with the rest of the
request completion being in blk-mq. That causes and out-of-line call
for each completion.
Move them into blk-mq.c instead, where they belong.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The fast path is no splitting needed. Separate the handling into a
check part we can inline, and an out-of-line handling path if we do
need to split.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Replace the blk_poll interface that requires the caller to keep a queue
and cookie from the submissions with polling based on the bio.
Polling for the bio itself leads to a few advantages:
- the cookie construction can made entirely private in blk-mq.c
- the caller does not need to remember the request_queue and cookie
separately and thus sidesteps their lifetime issues
- keeping the device and the cookie inside the bio allows to trivially
support polling BIOs remapping by stacking drivers
- a lot of code to propagate the cookie back up the submission path can
be removed entirely.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-15-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Unlike the RWF_HIPRI userspace ABI which is intentionally kept vague,
the bio flag is specific to the polling implementation, so rename and
document it properly.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-12-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There is no point in sleeping for the expected I/O completion timeout
in the io_uring async polling model as we never poll for a specific
I/O.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-11-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Switch the boolean spin argument to blk_poll to passing a set of flags
instead. This will allow to control polling behavior in a more fine
grained way.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-10-hch@lst.de
[axboe: adapt to changed io_uring iopoll]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Move the trivial check into the only caller.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-9-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Merge both functions into their only caller to keep the blk-mq tag to
blk_qc_t mapping as private as possible in blk-mq.c.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-8-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Factor the code to do the classic full metal polling out of blk_poll into
a separate blk_mq_poll_classic helper.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-7-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add a helper to get the hctx from a request_queue and cookie, and fold
the blk_qc_t_to_queue_num helper into it as no other callers are left.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add a blk_mq_get_tags() helper, which uses the new sbitmap API for
allocating a batch of tags all at once. This both simplifies the block
code for batched allocation, and it is also more efficient than just
doing repeated calls into __sbitmap_queue_get().
This reduces the sbitmap overhead in peak runs from ~3% to ~1% and
yields a performanc increase from 6.6M IOPS to 6.8M IOPS for a single
CPU core.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We already have a blk_mq_need_time_stamp() check in
__blk_mq_end_request() to get a timestamp, hide all the statistics
accounting under it. It cuts some cycles for requests that don't need
stats, and is free otherwise.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/e0f2ea812e93a8adcd07101212e7d7e70ca304e7.1634115360.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We could have a race here, where the request gets freed before we call
into blk_mq_run_hw_queue(). If this happens, we cannot rely on the state
of the request.
Grab the hardware context before inserting the flush.
Fixes: 0f38d76646 ("blk-mq: cleanup blk_mq_submit_bio")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Move the blk_mq_alloc_data stack allocation only into the branch
that actually needs it, and use rq->mq_hctx instead of data.hctx
to refer to the hctx.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211012104045.658051-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The newly added loop for the cached requests in __blk_mq_alloc_request
is a little too convoluted for my taste, so unwind it a bit. Also
rename the function to __blk_mq_alloc_requests now that it can allocate
more than a single request.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211012104045.658051-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The caller typically has a good (or even exact) idea of how many requests
it needs to submit. We can make the request/tag allocation a lot more
efficient if we just allocate N requests/tags upfront when we queue the
first bio from the batch.
Provide a new plug start helper that allows the caller to specify how many
IOs are expected. This sets plug->nr_ios, and we can use that for smarter
request allocation. The plug provides a holding spot for requests, and
request allocation will check it before calling into the normal request
allocation path.
The blk_finish_plug() is called, check if there are unused requests and
free them. This should not happen in normal operations. The exception is
if we get merging, then we may be left with requests that need freeing
when done.
This raises the per-core performance on my setup from ~5.8M to ~6.1M
IOPS.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Particularly for NVMe with efficient deferred submission for many
requests, there are nice benefits to be seen by bumping the default max
plug count from 16 to 32. This is especially true for virtualized setups,
where the submit part is more expensive. But can be noticed even on
native hardware.
Reduce the multiple queue factor from 4 to 2, since we're changing the
default size.
While changing it, move the defines into the block layer private header.
These aren't values that anyone outside of the block layer uses, or
should use.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Doing high IOPS testing with blk-cgroups enabled spends ~15-20% of the
time just doing ktime_get_ns() -> readtsc. We essentially read and
set the start time twice, one for the bio and then again when that bio
is mapped to a request.
Given that the time between the two is very short, inherit the bio
start time instead of reading it again. This cuts 1/3rd of the overhead
of the time keeping.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Now that we use shared tags for shared sbitmap support, we don't require
the tags sbitmap pointers, so drop them.
This essentially reverts commit 222a5ae03c ("blk-mq: Use pointers for
blk_mq_tags bitmap tags").
Function blk_mq_init_bitmap_tags() is removed also, since it would be only
a wrappper for blk_mq_init_bitmaps().
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1633429419-228500-14-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Currently we use separate sbitmap pairs and active_queues atomic_t for
shared sbitmap support.
However a full sets of static requests are used per HW queue, which is
quite wasteful, considering that the total number of requests usable at
any given time across all HW queues is limited by the shared sbitmap depth.
As such, it is considerably more memory efficient in the case of shared
sbitmap to allocate a set of static rqs per tag set or request queue, and
not per HW queue.
So replace the sbitmap pairs and active_queues atomic_t with a shared
tags per tagset and request queue, which will hold a set of shared static
rqs.
Since there is now no valid HW queue index to be passed to the blk_mq_ops
.init and .exit_request callbacks, pass an invalid index token. This
changes the semantics of the APIs, such that the callback would need to
validate the HW queue index before using it. Currently no user of shared
sbitmap actually uses the HW queue index (as would be expected).
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/1633429419-228500-13-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Refactor blk_mq_free_map_and_requests() such that it can be used at many
sites at which the tag map and rqs are freed.
Also rename to blk_mq_free_map_and_rqs(), which is shorter and matches the
alloc equivalent.
Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/1633429419-228500-12-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add a function to combine allocating tags and the associated requests,
and factor out common patterns to use this new function.
Some function only call blk_mq_alloc_map_and_rqs() now, but more
functionality will be added later.
Also make blk_mq_alloc_rq_map() and blk_mq_alloc_rqs() static since they
are only used in blk-mq.c, and finally rename some functions for
conciseness and consistency with other function names:
- __blk_mq_alloc_map_and_{request -> rqs}()
- blk_mq_alloc_{map_and_requests -> set_map_and_rqs}()
Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/1633429419-228500-11-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Put the functionality to update the sched shared sbitmap size in a common
function.
Since the same formula is always used to resize, and it can be got from
the request queue argument, so just pass the request queue pointer.
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/1633429419-228500-10-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Function blk_mq_clear_rq_mapping() is required to clear the sched tags
mappings in driver tags rqs[].
But there is no need for a driver tags to clear its own mapping, so skip
clearing the mapping in this scenario.
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/1633429419-228500-9-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Function blk_mq_clear_rq_mapping() will be used for shared sbitmap tags
in future, so pass a driver tags pointer instead of the tagset container
and HW queue index.
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/1633429419-228500-8-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
It's easier to read:
if (x)
X;
else
Y;
over:
if (!x)
Y;
else
X;
No functional change intended.
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/1633429419-228500-5-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For shared sbitmap, if the call to blk_mq_tag_update_depth() was
successful for any hctx when hctx->sched_tags is not set, then it would be
successful for all (due to nature in which blk_mq_tag_update_depth()
fails).
As such, there is no need to call blk_mq_tag_resize_shared_sbitmap() for
each hctx. So relocate the call until after the hctx iteration under the
!q->elevator check, which is equivalent (to !hctx->sched_tags).
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/1633429419-228500-4-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The original code in commit 24d2f90309 ("blk-mq: split out tag
initialization, support shared tags") would check tags->rqs is non-NULL and
then dereference tags->rqs[].
Then in commit 2af8cbe305 ("blk-mq: split tag ->rqs[] into two"), we
started to dereference tags->static_rqs[], but continued to check non-NULL
tags->rqs.
Check tags->static_rqs as non-NULL instead, which is more logical.
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/1633429419-228500-2-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Split the integrity/metadata handling definitions out into a new header.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210920123328.1399408-17-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There is no need to pull blk-cgroup.h and thus blkdev.h in here, so
break the include chain.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210920123328.1399408-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Don't switch back to percpu mode to avoid the double RCU grace period
when tearing down SCSI devices. After removing the disk only passthrough
commands can be send anyway.
Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20210929071241.934472-6-hch@lst.de
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Merge tag 'block-5.15-2021-09-11' of git://git.kernel.dk/linux-block
Pull block fixes from Jens Axboe:
- NVMe pull request from Christoph:
- fix nvmet command set reporting for passthrough controllers (Adam Manzanares)
- update a MAINTAINERS email address (Chaitanya Kulkarni)
- set QUEUE_FLAG_NOWAIT for nvme-multipth (me)
- handle errors from add_disk() (Luis Chamberlain)
- update the keep alive interval when kato is modified (Tatsuya Sasaki)
- fix a buffer overrun in nvmet_subsys_attr_serial (Hannes Reinecke)
- do not reset transport on data digest errors in nvme-tcp (Daniel Wagner)
- only call synchronize_srcu when clearing current path (Daniel Wagner)
- revalidate paths during rescan (Hannes Reinecke)
- Split out the fs/block_dev into block/fops.c and block/bdev.c, which
has been long overdue. Do this now before -rc1, to avoid annoying
conflicts due to this (Christoph)
- blk-throtl use-after-free fix (Li)
- Improve plug depth for multi-device plugs, greatly increasing md
resync performance (Song)
- blkdev_show() locking fix (Tetsuo)
- n64cart error check fix (Yang)
* tag 'block-5.15-2021-09-11' of git://git.kernel.dk/linux-block:
n64cart: fix return value check in n64cart_probe()
blk-mq: allow 4x BLK_MAX_REQUEST_COUNT at blk_plug for multiple_queues
block: move fs/block_dev.c to block/bdev.c
block: split out operations on block special files
blk-throttle: fix UAF by deleteing timer in blk_throtl_exit()
block: genhd: don't call blkdev_show() with major_names_lock held
nvme: update MAINTAINERS email address
nvme: add error handling support for add_disk()
nvme: only call synchronize_srcu when clearing current path
nvme: update keep alive interval when kato is modified
nvme-tcp: Do not reset transport on data digest errors
nvmet: fixup buffer overrun in nvmet_subsys_attr_serial()
nvmet: return bool from nvmet_passthru_ctrl and nvmet_is_passthru_req
nvmet: looks at the passthrough controller when initializing CAP
nvme: move nvme_multi_css into nvme.h
nvme-multipath: revalidate paths during rescan
nvme-multipath: set QUEUE_FLAG_NOWAIT
Limiting number of request to BLK_MAX_REQUEST_COUNT at blk_plug hurts
performance for large md arrays. [1] shows resync speed of md array drops
for md array with more than 16 HDDs.
Fix this by allowing more request at plug queue. The multiple_queue flag
is used to only apply higher limit to multiple queue cases.
[1] https://lore.kernel.org/linux-raid/CAFDAVznS71BXW8Jxv6k9dXc2iR3ysX3iZRBww_rzA8WifBFxGg@mail.gmail.com/
Tested-by: Marcin Wanat <marcin.wanat@gmail.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This series consists of the usual driver updates (ufs, qla2xxx,
target, smartpqi, lpfc, mpt3sas). The core change causing the most
churn was replacing the command request field request with a macro,
allowing us to offset map to it and remove the redundant field; the
same was also done for the tag field. The most impactful change is
the final removal of scsi_ioctl, which has been deprecated for over a
decade.
Signed-off-by: James E.J. Bottomley <jejb@linux.ibm.com>
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Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
Pull SCSI updates from James Bottomley:
"This series consists of the usual driver updates (ufs, qla2xxx,
target, smartpqi, lpfc, mpt3sas).
The core change causing the most churn was replacing the command
request field request with a macro, allowing us to offset map to it
and remove the redundant field; the same was also done for the tag
field.
The most impactful change is the final removal of scsi_ioctl, which
has been deprecated for over a decade"
* tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (293 commits)
scsi: ufs: Fix ufshcd_request_sense_async() for Samsung KLUFG8RHDA-B2D1
scsi: ufs: ufs-exynos: Fix static checker warning
scsi: mpt3sas: Use the proper SCSI midlayer interfaces for PI
scsi: lpfc: Use the proper SCSI midlayer interfaces for PI
scsi: lpfc: Copyright updates for 14.0.0.1 patches
scsi: lpfc: Update lpfc version to 14.0.0.1
scsi: lpfc: Add bsg support for retrieving adapter cmf data
scsi: lpfc: Add cmf_info sysfs entry
scsi: lpfc: Add debugfs support for cm framework buffers
scsi: lpfc: Add support for maintaining the cm statistics buffer
scsi: lpfc: Add rx monitoring statistics
scsi: lpfc: Add support for the CM framework
scsi: lpfc: Add cmfsync WQE support
scsi: lpfc: Add support for cm enablement buffer
scsi: lpfc: Add cm statistics buffer support
scsi: lpfc: Add EDC ELS support
scsi: lpfc: Expand FPIN and RDF receive logging
scsi: lpfc: Add MIB feature enablement support
scsi: lpfc: Add SET_HOST_DATA mbox cmd to pass date/time info to firmware
scsi: fc: Add EDC ELS definition
...
Core changes:
- The usual set of small fixes and improvements all over the place, but nothing
outstanding
MSI changes:
- Further consolidation of the PCI/MSI interrupt chip code
- Make MSI sysfs code independent of PCI/MSI and expose the MSI interrupts
of platform devices in the same way as PCI exposes them.
Driver changes:
- Support for ARM GICv3 EPPI partitions
- Treewide conversion to generic_handle_domain_irq() for all chained
interrupt controllers
- Conversion to bitmap_zalloc() throughout the irq chip drivers
- The usual set of small fixes and improvements
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Merge tag 'irq-core-2021-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull irq updates from Thomas Gleixner:
"Updates to the interrupt core and driver subsystems:
Core changes:
- The usual set of small fixes and improvements all over the place,
but nothing stands out
MSI changes:
- Further consolidation of the PCI/MSI interrupt chip code
- Make MSI sysfs code independent of PCI/MSI and expose the MSI
interrupts of platform devices in the same way as PCI exposes them.
Driver changes:
- Support for ARM GICv3 EPPI partitions
- Treewide conversion to generic_handle_domain_irq() for all chained
interrupt controllers
- Conversion to bitmap_zalloc() throughout the irq chip drivers
- The usual set of small fixes and improvements"
* tag 'irq-core-2021-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (57 commits)
platform-msi: Add ABI to show msi_irqs of platform devices
genirq/msi: Move MSI sysfs handling from PCI to MSI core
genirq/cpuhotplug: Demote debug printk to KERN_DEBUG
irqchip/qcom-pdc: Trim unused levels of the interrupt hierarchy
irqdomain: Export irq_domain_disconnect_hierarchy()
irqchip/gic-v3: Fix priority comparison when non-secure priorities are used
irqchip/apple-aic: Fix irq_disable from within irq handlers
pinctrl/rockchip: drop the gpio related codes
gpio/rockchip: drop irq_gc_lock/irq_gc_unlock for irq set type
gpio/rockchip: support next version gpio controller
gpio/rockchip: use struct rockchip_gpio_regs for gpio controller
gpio/rockchip: add driver for rockchip gpio
dt-bindings: gpio: change items restriction of clock for rockchip,gpio-bank
pinctrl/rockchip: add pinctrl device to gpio bank struct
pinctrl/rockchip: separate struct rockchip_pin_bank to a head file
pinctrl/rockchip: always enable clock for gpio controller
genirq: Fix kernel doc indentation
EDAC/altera: Convert to generic_handle_domain_irq()
powerpc: Bulk conversion to generic_handle_domain_irq()
nios2: Bulk conversion to generic_handle_domain_irq()
...
Replace the magic lookup through the kobject tree with an explicit
backpointer, given that the device model links are set up and torn
down at times when I/O is still possible, leading to potential
NULL or invalid pointer dereferences.
Fixes: edb0872f44 ("block: move the bdi from the request_queue to the gendisk")
Reported-by: syzbot <syzbot+aa0801b6b32dca9dda82@syzkaller.appspotmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Sven Schnelle <svens@linux.ibm.com>
Link: https://lore.kernel.org/r/20210816134624.GA24234@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pass in a request_queue and assign disk->queue in __blk_alloc_disk to
ensure struct gendisk always has a valid ->queue pointer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210816131910.615153-8-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This was a leftover from the legacy alloc_disk interface. Switch
the scsi ULPs and dasd to set ->minors directly like all other
drivers and remove the argument.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com> [dasd]
Link: https://lore.kernel.org/r/20210816131910.615153-7-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pass the lockdep name to the low-level __blk_alloc_disk helper and
hardcode the name for it given that the number of minors or node_id
are not very useful information. While this passes a pointless
argument for non-lockdep builds that is not really an issue as
disk allocation is a probe time only slow path.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210816131910.615153-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
is_flush_rq() is called from bt_iter()/bt_tags_iter(), and runs the
following check:
hctx->fq->flush_rq == req
but the passed hctx from bt_iter()/bt_tags_iter() may be NULL because:
1) memory re-order in blk_mq_rq_ctx_init():
rq->mq_hctx = data->hctx;
...
refcount_set(&rq->ref, 1);
OR
2) tag re-use and ->rqs[] isn't updated with new request.
Fix the issue by re-writing is_flush_rq() as:
return rq->end_io == flush_end_io;
which turns out simpler to follow and immune to data race since we have
ordered WRITE rq->end_io and refcount_set(&rq->ref, 1).
Fixes: 2e315dc07d ("blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter")
Cc: "Blank-Burian, Markus, Dr." <blankburian@uni-muenster.de>
Cc: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210818010925.607383-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Inside blk_mq_queue_tag_busy_iter() we already grabbed request's
refcount before calling ->fn(), so needn't to grab it one more time
in blk_mq_check_expired().
Meantime remove extra request expire check in blk_mq_check_expired().
Cc: Keith Busch <kbusch@kernel.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/20210811155202.629575-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We run a test that delete and recover devcies frequently(two devices on
the same host), and we found that 'active_queues' is super big after a
period of time.
If device a and device b share a tag set, and a is deleted, then
blk_mq_exit_queue() will clear BLK_MQ_F_TAG_QUEUE_SHARED because there
is only one queue that are using the tag set. However, if b is still
active, the active_queues of b might never be cleared even if b is
deleted.
Thus clear active_queues before BLK_MQ_F_TAG_QUEUE_SHARED is cleared.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210731062130.1533893-1-yukuai3@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With CONFIG_IRQ_FORCED_THREADING=y, testing the boolean force_irqthreads
could incur a cache line miss in invoke_softirq() and other places.
Replace the test with a static key to avoid the potential cache miss.
[ tglx: Dropped the IDE part, removed the export and updated blk-mq ]
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Tanner Love <tannerlove@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210602180338.3324213-1-tannerlove.kernel@gmail.com
The backing device information only makes sense for file system I/O,
and thus belongs into the gendisk and not the lower level request_queue
structure. Move it there.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210809141744.1203023-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Move the sg_timeout and sg_reserved_size fields into the bsg_device and
scsi_device structures as they have nothing to do with generic block I/O.
Note that these values are now separate for bsg vs. SCSI device node
access, but that just matches how /dev/sg vs the other nodes has always
behaved.
Link: https://lore.kernel.org/r/20210729064845.1044147-4-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Commit 6e6fcbc27e ("blk-mq: support batching dispatch in case of io")
starts to support io batching submission by using hctx->dispatch_busy.
However, blk_mq_update_dispatch_busy() isn't changed to update hctx->dispatch_busy
in that commit, so fix the issue by updating hctx->dispatch_busy in case
of real scheduler.
Reported-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Fixes: 6e6fcbc27e ("blk-mq: support batching dispatch in case of io")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210625020248.1630497-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Change the type and name of task_struct::state. Drop the volatile and
shrink it to an 'unsigned int'. Rename it in order to find all uses
such that we can use READ_ONCE/WRITE_ONCE as appropriate.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20210611082838.550736351@infradead.org
Replace a bunch of 'p->state == TASK_RUNNING' with a new helper:
task_is_running(p).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210611082838.222401495@infradead.org
Add a new API to allocate a gendisk including the request_queue for use
with blk-mq based drivers. This is to avoid boilerplate code in drivers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Link: https://lore.kernel.org/r/20210602065345.355274-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Don't return the passed in request_queue but a normal error code, and
drop the elevator_init argument in favor of just calling elevator_init_mq
directly from dm-rq.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Link: https://lore.kernel.org/r/20210602065345.355274-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Factour out a helper to initialize a simple single hw queue tag_set from
blk_mq_init_sq_queue. This will allow to phase out blk_mq_init_sq_queue
in favor of a more symmetric and general API.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Link: https://lore.kernel.org/r/20210602065345.355274-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Provided the device driver does not implement dispatch budget accounting
(which only SCSI does) the loop in __blk_mq_do_dispatch_sched() pulls
requests from the IO scheduler as long as it is willing to give out any.
That defeats scheduling heuristics inside the scheduler by creating
false impression that the device can take more IO when it in fact
cannot.
For example with BFQ IO scheduler on top of virtio-blk device setting
blkio cgroup weight has barely any impact on observed throughput of
async IO because __blk_mq_do_dispatch_sched() always sucks out all the
IO queued in BFQ. BFQ first submits IO from higher weight cgroups but
when that is all dispatched, it will give out IO of lower weight cgroups
as well. And then we have to wait for all this IO to be dispatched to
the disk (which means lot of it actually has to complete) before the
IO scheduler is queried again for dispatching more requests. This
completely destroys any service differentiation.
So grab request tag for a request pulled out of the IO scheduler already
in __blk_mq_do_dispatch_sched() and do not pull any more requests if we
cannot get it because we are unlikely to be able to dispatch it. That
way only single request is going to wait in the dispatch list for some
tag to free.
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210603104721.6309-1-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The tags used for an IO scheduler are currently per hctx.
As such, when q->nr_hw_queues grows, so does the request queue total IO
scheduler tag depth.
This may cause problems for SCSI MQ HBAs whose total driver depth is
fixed.
Ming and Yanhui report higher CPU usage and lower throughput in scenarios
where the fixed total driver tag depth is appreciably lower than the total
scheduler tag depth:
https://lore.kernel.org/linux-block/440dfcfc-1a2c-bd98-1161-cec4d78c6dfc@huawei.com/T/#mc0d6d4f95275a2743d1c8c3e4dc9ff6c9aa3a76b
In that scenario, since the scheduler tag is got first, much contention
is introduced since a driver tag may not be available after we have got
the sched tag.
Improve this scenario by introducing request queue-wide tags for when
a tagset-wide sbitmap is used. The static sched requests are still
allocated per hctx, as requests are initialised per hctx, as in
blk_mq_init_request(..., hctx_idx, ...) ->
set->ops->init_request(.., hctx_idx, ...).
For simplicity of resizing the request queue sbitmap when updating the
request queue depth, just init at the max possible size, so we don't need
to deal with the possibly with swapping out a new sbitmap for old if
we need to grow.
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/1620907258-30910-3-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The tag allocation code to alloc the sbitmap pairs is common for regular
bitmaps tags and shared sbitmap, so refactor into a common function.
Also remove superfluous "flags" argument from blk_mq_init_shared_sbitmap().
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/1620907258-30910-2-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Before we free request queue, clearing flush request reference in
tags->rqs[], so that potential UAF can be avoided.
Based on one patch written by David Jeffery.
Tested-by: John Garry <john.garry@huawei.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: David Jeffery <djeffery@redhat.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210511152236.763464-5-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
refcount_inc_not_zero() in bt_tags_iter() still may read one freed
request.
Fix the issue by the following approach:
1) hold a per-tags spinlock when reading ->rqs[tag] and calling
refcount_inc_not_zero in bt_tags_iter()
2) clearing stale request referred via ->rqs[tag] before freeing
request pool, the per-tags spinlock is held for clearing stale
->rq[tag]
So after we cleared stale requests, bt_tags_iter() won't observe
freed request any more, also the clearing will wait for pending
request reference.
The idea of clearing ->rqs[] is borrowed from John Garry's previous
patch and one recent David's patch.
Tested-by: John Garry <john.garry@huawei.com>
Reviewed-by: David Jeffery <djeffery@redhat.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210511152236.763464-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter(), and
this way will prevent the request from being re-used when ->fn is
running. The approach is same as what we do during handling timeout.
Fix request use-after-free(UAF) related with completion race or queue
releasing:
- If one rq is referred before rq->q is frozen, then queue won't be
frozen before the request is released during iteration.
- If one rq is referred after rq->q is frozen, refcount_inc_not_zero()
will return false, and we won't iterate over this request.
However, still one request UAF not covered: refcount_inc_not_zero() may
read one freed request, and it will be handled in next patch.
Tested-by: John Garry <john.garry@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210511152236.763464-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
