After commit 4e5cc99e1e ("blk-mq: manage hctx map via xarray"), we use
an xarray instead of array to store hctx, but in poll mode, each time
in blk_mq_poll, we need use xa_load to find corresponding hctx, this
introduce some costs. In my test, xa_load may cost 3.8% cpu.
This patch revert previous change, eliminates the overhead of xa_load
and can result in a 3% performance improvement.
Signed-off-by: Fengnan Chang <changfengnan@bytedance.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit 7f2799c546 ("blk-mq: cleanup shared tags case in
blk_mq_update_nr_requests()") moves blk_mq_tag_update_sched_shared_tags()
before q->nr_requests is updated, however, it's still using the old
q->nr_requests to resize tag depth.
Fix this problem by passing in expected new tag depth.
Fixes: 7f2799c546 ("blk-mq: cleanup shared tags case in blk_mq_update_nr_requests()")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reported-by: Chris Mason <clm@meta.com>
Link: https://lore.kernel.org/linux-block/20251014130507.4187235-2-clm@meta.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_mq_free_tags() can be called after blk_mq_init_tags(), while
tags->page_list is still not initialized, causing null-ptr-deref.
Fix this problem by initializing tags->page_list at blk_mq_init_tags(),
meanwhile, also free tags directly from error path because there is no
srcu barrier.
Fixes: ad0d05dbdd ("blk-mq: Defer freeing of tags page_list to SRCU callback")
Reported-by: syzbot+5c5d41e80248d610221f@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68d1b079.a70a0220.1b52b.0000.GAE@google.com/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit 8ab30a3319 ("blk-mq: Drop busy_iter_fn blk_mq_hw_ctx argument")
removed the hctx argument from the callback functions called by
bt_for_each() and blk_mq_queue_tag_busy_iter(). Commit 2dd6532e95
("blk-mq: Drop 'reserved' arg of busy_tag_iter_fn") removed the
'reserved' argument of the busy_tag_iter_fn function pointer type. Bring
the documentation of the tag iteration functions in sync with these
changes.
Cc: John Garry <john.g.garry@oracle.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit 2dd6532e95 ("blk-mq: Drop 'reserved' arg of busy_tag_iter_fn")
removed the 'reserved' argument from tag iteration callback functions.
Bring the blk_mq_tagset_busy_iter() documentation in sync with that
change.
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: John Garry <john.g.garry@oracle.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This helper is not used now.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For shared tags case, all hctx->sched_tags/tags are the same, it doesn't
make sense to call into blk_mq_tag_update_depth() multiple times for the
same tags.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
queue_requests_store() is the only caller of
blk_mq_update_nr_requests(), and blk_mq_update_nr_requests() is the
only caller of blk_mq_tag_update_depth(), however, they all have
checkings for nr_requests input by user.
Make code cleaner by moving all the checkings to the top function:
1) nr_requests > reserved tags;
2) if there is elevator, 4 <= nr_requests <= 2048;
3) if elevator is none, 4 <= nr_requests <= tag_set->queue_depth;
Meanwhile, case 2 is the only case tags can grow and -ENOMEM might be
returned.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Replace the spinlock in blk_mq_find_and_get_req() with an SRCU read lock
around the tag iterators.
This is done by:
- Holding the SRCU read lock in blk_mq_queue_tag_busy_iter(),
blk_mq_tagset_busy_iter(), and blk_mq_hctx_has_requests().
- Removing the now-redundant tags->lock from blk_mq_find_and_get_req().
This change fixes lockup issue in scsi_host_busy() in case of shost->host_blocked.
Also avoids big tags->lock when reading disk sysfs attribute `inflight`.
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Tag iterators can race with the freeing of the request pages(tags->page_list),
potentially leading to use-after-free issues.
Defer the freeing of the page list and the tags structure itself until
after an SRCU grace period has passed. This ensures that any concurrent
tag iterators have completed before the memory is released. With this
way, we can replace the big tags->lock in tags iterator code path with
srcu for solving the issue.
This is achieved by:
- Adding a new `srcu_struct tags_srcu` to `blk_mq_tag_set` to protect
tag map iteration.
- Adding an `rcu_head` to `struct blk_mq_tags` to be used with
`call_srcu`.
- Moving the page list freeing logic and the `kfree(tags)` call into a
new callback function, `blk_mq_free_tags_callback`.
- In `blk_mq_free_tags`, invoking `call_srcu` to schedule the new
callback for deferred execution.
The read-side protection for the tag iterators will be added in a
subsequent patch.
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
To prepare for converting the tag->rqs freeing to be SRCU-based, the
tag_set is needed in the freeing helper functions.
This patch adds 'struct blk_mq_tag_set *' as the first parameter to
blk_mq_free_rq_map() and blk_mq_free_tags(), and updates all their call
sites.
This allows access to the tag_set's SRCU structure in the next step,
which will be used to free the tag maps after a grace period.
No functional change is intended in this patch.
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In the case user trigger tags grow by queue sysfs attribute nr_requests,
hctx->sched_tags will be freed directly and replaced with a new
allocated tags, see blk_mq_tag_update_depth().
The problem is that hctx->sched_tags is from elevator->et->tags, while
et->tags is still the freed tags, hence later elevator exit will try to
free the tags again, causing kernel panic.
Fix this problem by replacing et->tags with new allocated tags as well.
Noted there are still some long term problems that will require some
refactor to be fixed thoroughly[1].
[1] https://lore.kernel.org/all/20250815080216.410665-1-yukuai1@huaweicloud.com/
Fixes: f5a6604f7a ("block: fix lockdep warning caused by lock dependency in elv_iosched_store")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Li Nan <linan122@huawei.com>
Link: https://lore.kernel.org/r/20250821060612.1729939-3-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Use a plain BLK_MQ_F_* flag to select the round robin tag selection
instead of overlaying an enum with just two possible values into the
flags space.
Doing so allows adding a BLK_MQ_F_MAX sentinel for simplified overflow
checking in the messy debugfs helpers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20250106083531.799976-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The little work done in blk_mq_init_bitmaps is easier done in the only
caller.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20250106083531.799976-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Merge tag 'for-6.5/block-2023-06-23' of git://git.kernel.dk/linux
Pull block updates from Jens Axboe:
- NVMe pull request via Keith:
- Various cleanups all around (Irvin, Chaitanya, Christophe)
- Better struct packing (Christophe JAILLET)
- Reduce controller error logs for optional commands (Keith)
- Support for >=64KiB block sizes (Daniel Gomez)
- Fabrics fixes and code organization (Max, Chaitanya, Daniel
Wagner)
- bcache updates via Coly:
- Fix a race at init time (Mingzhe Zou)
- Misc fixes and cleanups (Andrea, Thomas, Zheng, Ye)
- use page pinning in the block layer for dio (David)
- convert old block dio code to page pinning (David, Christoph)
- cleanups for pktcdvd (Andy)
- cleanups for rnbd (Guoqing)
- use the unchecked __bio_add_page() for the initial single page
additions (Johannes)
- fix overflows in the Amiga partition handling code (Michael)
- improve mq-deadline zoned device support (Bart)
- keep passthrough requests out of the IO schedulers (Christoph, Ming)
- improve support for flush requests, making them less special to deal
with (Christoph)
- add bdev holder ops and shutdown methods (Christoph)
- fix the name_to_dev_t() situation and use cases (Christoph)
- decouple the block open flags from fmode_t (Christoph)
- ublk updates and cleanups, including adding user copy support (Ming)
- BFQ sanity checking (Bart)
- convert brd from radix to xarray (Pankaj)
- constify various structures (Thomas, Ivan)
- more fine grained persistent reservation ioctl capability checks
(Jingbo)
- misc fixes and cleanups (Arnd, Azeem, Demi, Ed, Hengqi, Hou, Jan,
Jordy, Li, Min, Yu, Zhong, Waiman)
* tag 'for-6.5/block-2023-06-23' of git://git.kernel.dk/linux: (266 commits)
scsi/sg: don't grab scsi host module reference
ext4: Fix warning in blkdev_put()
block: don't return -EINVAL for not found names in devt_from_devname
cdrom: Fix spectre-v1 gadget
block: Improve kernel-doc headers
blk-mq: don't insert passthrough request into sw queue
bsg: make bsg_class a static const structure
ublk: make ublk_chr_class a static const structure
aoe: make aoe_class a static const structure
block/rnbd: make all 'class' structures const
block: fix the exclusive open mask in disk_scan_partitions
block: add overflow checks for Amiga partition support
block: change all __u32 annotations to __be32 in affs_hardblocks.h
block: fix signed int overflow in Amiga partition support
block: add capacity validation in bdev_add_partition()
block: fine-granular CAP_SYS_ADMIN for Persistent Reservation
block: disallow Persistent Reservation on partitions
reiserfs: fix blkdev_put() warning from release_journal_dev()
block: fix wrong mode for blkdev_get_by_dev() from disk_scan_partitions()
block: document the holder argument to blkdev_get_by_path
...
In __blk_mq_tag_busy/idle(), updating 'active_queues' and calculating
'wake_batch' is not atomic:
t1: t2:
_blk_mq_tag_busy blk_mq_tag_busy
inc active_queues
// assume 1->2
inc active_queues
// 2 -> 3
blk_mq_update_wake_batch
// calculate based on 3
blk_mq_update_wake_batch
/* calculate based on 2, while active_queues is actually 3. */
Fix this problem by protecting them wih 'tags->lock', this is not a hot
path, so performance should not be concerned. And now that all writers
are inside the lock, switch 'actives_queues' from atomic to unsigned
int.
Fixes: 180dccb0db ("blk-mq: fix tag_get wait task can't be awakened")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230610023043.2559121-1-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If multiple CPUs are sharing the same hardware queue, it can
cause leak in the active queue counter tracking when __blk_mq_tag_busy()
is executed simultaneously.
Fixes: ee78ec1077 ("blk-mq: blk_mq_tag_busy is no need to return a value")
Signed-off-by: Tian Lan <tian.lan@twosigma.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20230522210555.794134-1-tilan7663@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block/blk-mq.h needs various definitions from <linux/blk-mq.h>,
include it there instead of relying on the source files to include
both.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230413064057.707578-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk-mq-tag.h is always included by blk-mq.h, and causes recursive
inclusion hell with further changes. Just merge it into blk-mq.h
instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230413064057.707578-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This reverts commit 16ede66973.
This is causing issues with CPU stalls on my test box, revert it for
now until we understand what is going on. It looks like infinite
looping off sbitmap_queue_wake_up(), but hard to tell with a lot of
CPUs hitting this issue and the console scrolling infinitely.
Link: https://lore.kernel.org/linux-block/e742813b-ce5c-0d58-205b-1626f639b1bd@kernel.dk/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The local variable is now only referenced once so drop it.
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/1657109034-206040-7-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We no longer use the 'reserved' arg in busy_tag_iter_fn for any iter
function so it may be dropped.
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me> #nvme
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/1657109034-206040-6-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Since the if condition in blk_mq_put_tag() checks that the tag to put is
not a reserved one, the BUG_ON() check in the else branch checking if
the tag is indeed a reserved one is useless. Remove it.
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20220602075159.1273366-1-damien.lemoal@opensource.wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
First code becomes more clean by switching to xarray from plain array.
Second use-after-free on q->queue_hw_ctx can be fixed because
queue_for_each_hw_ctx() may be run when updating nr_hw_queues is
in-progress. With this patch, q->hctx_table is defined as xarray, and
this structure will share same lifetime with request queue, so
queue_for_each_hw_ctx() can use q->hctx_table to lookup hctx reliably.
Reported-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220308073219.91173-7-ming.lei@redhat.com
[axboe: fix blk_mq_hw_ctx forward declaration]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
It is inevitable to cause use-after-free on q->queue_hw_ctx between
queue_for_each_hw_ctx() and blk_mq_update_nr_hw_queues(). And converting
to xarray can fix the uaf, meantime code gets cleaner.
Prepare for converting q->queue_hctx_ctx into xarray, one thing is that
xa_for_each() can only accept 'unsigned long' as index, so changes type
of hctx index of queue_for_each_hw_ctx() into 'unsigned long'.
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220308073219.91173-6-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Since __sbitmap_queue_get_shallow() was introduced in commit c05e667337
("sbitmap: add sbitmap_get_shallow() operation"), it has not been used.
Delete __sbitmap_queue_get_shallow() and rename public
__sbitmap_queue_get_shallow() -> sbitmap_queue_get_shallow() as it is odd
to have public __foo but no foo at all.
Signed-off-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1644322024-105340-1-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In case of shared tags, there might be more than one hctx which
allocates from the same tags, and each hctx is limited to allocate at
most:
hctx_max_depth = max((bt->sb.depth + users - 1) / users, 4U);
tag idle detection is lazy, and may be delayed for 30sec, so there
could be just one real active hctx(queue) but all others are actually
idle and still accounted as active because of the lazy idle detection.
Then if wake_batch is > hctx_max_depth, driver tag allocation may wait
forever on this real active hctx.
Fix this by recalculating wake_batch when inc or dec active_queues.
Fixes: 0d2602ca30 ("blk-mq: improve support for shared tags maps")
Suggested-by: Ming Lei <ming.lei@redhat.com>
Suggested-by: John Garry <john.garry@huawei.com>
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220113025536.1479653-1-qiulaibin@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Kashyap reports high CPU usage in blk_mq_queue_tag_busy_iter() and callees
using megaraid SAS RAID card since moving to shared tags [0].
Previously, when shared tags was shared sbitmap, this function was less
than optimum since we would iter through all tags for all hctx's,
yet only ever match upto tagset depth number of rqs.
Since the change to shared tags, things are even less efficient if we have
parallel callers of blk_mq_queue_tag_busy_iter(). This is because in
bt_iter() -> blk_mq_find_and_get_req() there would be more contention on
accessing each request ref and tags->lock since they are now shared among
all HW queues.
Optimise by having separate calls to bt_for_each() for when we're using
shared tags. In this case no longer pass a hctx, as it is no longer
relevant, and teach bt_iter() about this.
Ming suggested something along the lines of this change, apart from a
different implementation.
[0] https://lore.kernel.org/linux-block/e4e92abbe9d52bcba6b8cc6c91c442cc@mail.gmail.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>
Reported-and-tested-by: Kashyap Desai <kashyap.desai@broadcom.com>
Fixes: e155b0c238 ("blk-mq: Use shared tags for shared sbitmap support")
Link: https://lore.kernel.org/r/1638794990-137490-4-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Typedefs busy_iter_fn and busy_tag_iter_fn are now identical, so delete
busy_iter_fn to reduce duplication.
It would be nicer to delete busy_tag_iter_fn, as the name busy_iter_fn is
less specific.
However busy_tag_iter_fn is used in many different parts of the tree,
unlike busy_iter_fn which is just use in block/, so just take the
straightforward path now, so that we could rename later treewide.
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Kashyap Desai <kashyap.desai@broadcom.com>
Link: https://lore.kernel.org/r/1638794990-137490-3-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The only user of blk_mq_hw_ctx blk_mq_hw_ctx argument is
blk_mq_rq_inflight().
Function blk_mq_rq_inflight() uses the hctx to find the associated request
queue to match against the request. However this same check is already
done in caller bt_iter(), so drop this check.
With that change there are no more users of busy_iter_fn blk_mq_hw_ctx
argument, so drop the argument.
Reviewed-by Hannes Reinecke <hare@suse.de>
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Kashyap Desai <kashyap.desai@broadcom.com>
Link: https://lore.kernel.org/r/1638794990-137490-2-git-send-email-john.garry@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
refcount_t is not as expensive as it used to be, but it's still more
expensive than the io_uring method of using atomic_t and just checking
for potential over/underflow.
This borrows that same implementation, which in turn is based on the
mm implementation from Linus.
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Since it is now possible for a tagset to share a single set of tags, the
iter function should not re-iter the tags for the count of #hw queues in
that case. Rather it should just iter once.
Fixes: e155b0c238 ("blk-mq: Use shared tags for shared sbitmap support")
Reported-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Kashyap Desai <kashyap.desai@broadcom.com>
Link: https://lore.kernel.org/r/1634550083-202815-1-git-send-email-john.garry@huawei.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>
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>
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>
blk-mq can't run allocating driver tag and updating ->rqs[tag]
atomically, meantime blk-mq doesn't clear ->rqs[tag] after the driver
tag is released.
So there is chance to iterating over one stale request just after the
tag is allocated and before updating ->rqs[tag].
scsi_host_busy_iter() calls scsi_host_check_in_flight() to count scsi
in-flight requests after scsi host is blocked, so no new scsi command can
be marked as SCMD_STATE_INFLIGHT. However, driver tag allocation still can
be run by blk-mq core. One request is marked as SCMD_STATE_INFLIGHT,
but this request may have been kept in another slot of ->rqs[], meantime
the slot can be allocated out but ->rqs[] isn't updated yet. Then this
in-flight request is counted twice as SCMD_STATE_INFLIGHT. This way causes
trouble in handling scsi error.
Fixes the issue by not iterating over stale request.
Cc: linux-scsi@vger.kernel.org
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Reported-by: luojiaxing <luojiaxing@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210906065003.439019-1-ming.lei@redhat.com
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>
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>
Fengnan Chang