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->elevator_lock depends on queue freeze lock, see block/blk-sysfs.c.
queue freeze lock depends on fs_reclaim.
So don't grab elevator lock during queue initialization which needs to
call kmalloc(GFP_KERNEL), and we can cut the dependency between
->elevator_lock and fs_reclaim, then the lockdep warning can be killed.
This way is safe because elevator setting isn't ready to run during
queue initialization.
There isn't such issue in __blk_mq_update_nr_hw_queues() because
memalloc_noio_save() is called before acquiring elevator lock.
Fixes the following lockdep warning:
https://lore.kernel.org/linux-block/67e6b425.050a0220.2f068f.007b.GAE@google.com/
Reported-by: syzbot+4c7e0f9b94ad65811efb@syzkaller.appspotmail.com
Cc: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250403105402.1334206-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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We are no longer using nr_segs, after blk_mq_attempt_bio_merge was moved
out of blk_mq_get_new_request.
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Link: https://lore.kernel.org/r/20250401044348.15588-1-nj.shetty@samsung.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The blk_mq_map_queue()'s request_queue param is not used anymore,
remove it, same with blk_get_flush_queue().
Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250312084722.129680-1-kanie@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Make sure ->nr_integrity_segments is cloned in blk_rq_prep_clone(),
otherwise requests cloned by device-mapper multipath will not have the
proper nr_integrity_segments values set, then BUG() is hit from
sg_alloc_table_chained().
Fixes: b0fd271d5fba ("block: add request clone interface (v2)")
Cc: stable@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250310115453.2271109-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Currently, hctx attributes (nr_tags, nr_reserved_tags, and cpu_list)
are protected using `q->sysfs_lock`. However, these attributes can be
updated in multiple scenarios:
- During the driver's probe method.
- When updating nr_hw_queues.
- When writing to the sysfs attribute nr_requests,
which can modify nr_tags.
The nr_requests attribute is already protected using q->elevator_lock,
but none of the update paths actually use q->sysfs_lock to protect hctx
attributes. So to ensure proper synchronization, replace q->sysfs_lock
with q->elevator_lock when reading hctx attributes through sysfs.
Additionally, blk_mq_update_nr_hw_queues allocates and updates hctx.
The allocation of hctx is protected using q->elevator_lock, however,
updating hctx params happens without any protection, so safeguard hctx
param update path by also using q->elevator_lock.
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250306093956.2818808-1-nilay@linux.ibm.com
[axboe: wrap comment at 80 chars]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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A queue's elevator can be updated either when modifying nr_hw_queues
or through the sysfs scheduler attribute. Currently, elevator switching/
updating is protected using q->sysfs_lock, but this has led to lockdep
splats[1] due to inconsistent lock ordering between q->sysfs_lock and
the freeze-lock in multiple block layer call sites.
As the scope of q->sysfs_lock is not well-defined, its (mis)use has
resulted in numerous lockdep warnings. To address this, introduce a new
q->elevator_lock, dedicated specifically for protecting elevator
switches/updates. And we'd now use this new q->elevator_lock instead of
q->sysfs_lock for protecting elevator switches/updates.
While at it, make elv_iosched_load_module() a static function, as it is
only called from elv_iosched_store(). Also, remove redundant parameters
from elv_iosched_load_module() function signature.
[1] https://lore.kernel.org/all/67637e70.050a0220.3157ee.000c.GAE@google.com/
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250304102551.2533767-5-nilay@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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When block drivers or the core block code perform allocations with a
frozen queue, this could try to recurse into the block device to
reclaim memory and deadlock. Thus all allocations done by a process
that froze a queue need to be done without __GFP_IO and __GFP_FS.
Instead of tying to track all of them down, force a noio scope as
part of freezing the queue.
Note that nvme is a bit of a mess here due to the non-owner freezes,
and they will be addressed separately.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250131120352.1315351-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The error handling code in blk_mq_get_new_requests() cannot be understood
without knowing that this function is only called by blk_mq_submit_bio().
Hence move the code for handling blk_mq_get_new_requests() failures into
blk_mq_submit_bio().
Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20241218212246.1073149-3-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Help the CPU branch predictor in case of a cache hit by handling the cache
hit scenario first.
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20241218212246.1073149-2-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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When __blk_mq_update_nr_hw_queues changes the number of tag sets, it
might have to disable poll queues. Currently it does so by adjusting
the BLK_FEAT_POLL, which is a bit against the intent of features that
describe hardware / driver capabilities, but more importantly causes
nasty lock order problems with the broadly held freeze when updating the
number of hardware queues and the limits lock. Fix this by leaving
BLK_FEAT_POLL alone, and instead check for the number of poll queues in
the bio submission and poll handlers. While this adds extra work to the
fast path, the variables are in cache lines used by these operations
anyway, so it should be cheap enough.
Fixes: 8023e144f9d6 ("block: move the poll flag to queue_limits")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Link: https://lore.kernel.org/r/20250110054726.1499538-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Otherwise feature reconfiguration can race with I/O submission.
Also drop the bio_clear_polled in the error path, as the flag does not
matter for instant error completions, it is a left over from when we
allowed polled I/O to proceed unpolled in this case.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20250110054726.1499538-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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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>
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There is not real point in a helper just to assign three values to four
fields, especially when the surrounding code is working on the
neighbor fields directly.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Link: https://lore.kernel.org/r/20250103073417.459715-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Now we only verify the outmost freeze & unfreeze in current context in case
that !q->mq_freeze_depth, so it is reliable to save queue lying state when
we want to lock the freeze queue since the state is one per-task variable
now.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241127135133.3952153-5-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Now we only verify the outmost freeze & unfreeze in current context in case
that !q->mq_freeze_depth, so it is reliable to save disk DEAD state when
we want to lock the freeze queue since the state is one per-task variable
now.
Doing this way can kill lots of false positive when freeze queue is
called before adding disk[1].
[1] https://lore.kernel.org/linux-block/6741f6b2.050a0220.1cc393.0017.GAE@google.com/
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241127135133.3952153-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The following check of 'q->mq_freeze_owner != current' covers the
previous one, so remove the unnecessary check.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241127135133.3952153-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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If the 'hctx' isn't removed from cpuhp callback list, we can't reuse it,
otherwise use-after-free may be triggered.
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202412172217.b906db7c-lkp@intel.com
Tested-by: kernel test robot <oliver.sang@intel.com>
Fixes: 22465bbac53c ("blk-mq: move cpuhp callback registering out of q->sysfs_lock")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241218101617.3275704-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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acquiring sysfs_lock"
This reverts commit be26ba96421ab0a8fa2055ccf7db7832a13c44d2.
Commit be26ba96421a ("block: Fix potential deadlock while freezing queue and
acquiring sysfs_loc") actually reverts commit 22465bbac53c ("blk-mq: move cpuhp
callback registering out of q->sysfs_lock"), and causes the original resctrl
lockdep warning.
So revert it and we need to fix the issue in another way.
Cc: Nilay Shroff <nilay@linux.ibm.com>
Fixes: be26ba96421a ("block: Fix potential deadlock while freezing queue and acquiring sysfs_loc")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241218101617.3275704-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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For storing a value to a queue attribute, the queue_attr_store function
first freezes the queue (->q_usage_counter(io)) and then acquire
->sysfs_lock. This seems not correct as the usual ordering should be to
acquire ->sysfs_lock before freezing the queue. This incorrect ordering
causes the following lockdep splat which we are able to reproduce always
simply by accessing /sys/kernel/debug file using ls command:
[ 57.597146] WARNING: possible circular locking dependency detected
[ 57.597154] 6.12.0-10553-gb86545e02e8c #20 Tainted: G W
[ 57.597162] ------------------------------------------------------
[ 57.597168] ls/4605 is trying to acquire lock:
[ 57.597176] c00000003eb56710 (&mm->mmap_lock){++++}-{4:4}, at: __might_fault+0x58/0xc0
[ 57.597200]
but task is already holding lock:
[ 57.597207] c0000018e27c6810 (&sb->s_type->i_mutex_key#3){++++}-{4:4}, at: iterate_dir+0x94/0x1d4
[ 57.597226]
which lock already depends on the new lock.
[ 57.597233]
the existing dependency chain (in reverse order) is:
[ 57.597241]
-> #5 (&sb->s_type->i_mutex_key#3){++++}-{4:4}:
[ 57.597255] down_write+0x6c/0x18c
[ 57.597264] start_creating+0xb4/0x24c
[ 57.597274] debugfs_create_dir+0x2c/0x1e8
[ 57.597283] blk_register_queue+0xec/0x294
[ 57.597292] add_disk_fwnode+0x2e4/0x548
[ 57.597302] brd_alloc+0x2c8/0x338
[ 57.597309] brd_init+0x100/0x178
[ 57.597317] do_one_initcall+0x88/0x3e4
[ 57.597326] kernel_init_freeable+0x3cc/0x6e0
[ 57.597334] kernel_init+0x34/0x1cc
[ 57.597342] ret_from_kernel_user_thread+0x14/0x1c
[ 57.597350]
-> #4 (&q->debugfs_mutex){+.+.}-{4:4}:
[ 57.597362] __mutex_lock+0xfc/0x12a0
[ 57.597370] blk_register_queue+0xd4/0x294
[ 57.597379] add_disk_fwnode+0x2e4/0x548
[ 57.597388] brd_alloc+0x2c8/0x338
[ 57.597395] brd_init+0x100/0x178
[ 57.597402] do_one_initcall+0x88/0x3e4
[ 57.597410] kernel_init_freeable+0x3cc/0x6e0
[ 57.597418] kernel_init+0x34/0x1cc
[ 57.597426] ret_from_kernel_user_thread+0x14/0x1c
[ 57.597434]
-> #3 (&q->sysfs_lock){+.+.}-{4:4}:
[ 57.597446] __mutex_lock+0xfc/0x12a0
[ 57.597454] queue_attr_store+0x9c/0x110
[ 57.597462] sysfs_kf_write+0x70/0xb0
[ 57.597471] kernfs_fop_write_iter+0x1b0/0x2ac
[ 57.597480] vfs_write+0x3dc/0x6e8
[ 57.597488] ksys_write+0x84/0x140
[ 57.597495] system_call_exception+0x130/0x360
[ 57.597504] system_call_common+0x160/0x2c4
[ 57.597516]
-> #2 (&q->q_usage_counter(io)#21){++++}-{0:0}:
[ 57.597530] __submit_bio+0x5ec/0x828
[ 57.597538] submit_bio_noacct_nocheck+0x1e4/0x4f0
[ 57.597547] iomap_readahead+0x2a0/0x448
[ 57.597556] xfs_vm_readahead+0x28/0x3c
[ 57.597564] read_pages+0x88/0x41c
[ 57.597571] page_cache_ra_unbounded+0x1ac/0x2d8
[ 57.597580] filemap_get_pages+0x188/0x984
[ 57.597588] filemap_read+0x13c/0x4bc
[ 57.597596] xfs_file_buffered_read+0x88/0x17c
[ 57.597605] xfs_file_read_iter+0xac/0x158
[ 57.597614] vfs_read+0x2d4/0x3b4
[ 57.597622] ksys_read+0x84/0x144
[ 57.597629] system_call_exception+0x130/0x360
[ 57.597637] system_call_common+0x160/0x2c4
[ 57.597647]
-> #1 (mapping.invalidate_lock#2){++++}-{4:4}:
[ 57.597661] down_read+0x6c/0x220
[ 57.597669] filemap_fault+0x870/0x100c
[ 57.597677] xfs_filemap_fault+0xc4/0x18c
[ 57.597684] __do_fault+0x64/0x164
[ 57.597693] __handle_mm_fault+0x1274/0x1dac
[ 57.597702] handle_mm_fault+0x248/0x484
[ 57.597711] ___do_page_fault+0x428/0xc0c
[ 57.597719] hash__do_page_fault+0x30/0x68
[ 57.597727] do_hash_fault+0x90/0x35c
[ 57.597736] data_access_common_virt+0x210/0x220
[ 57.597745] _copy_from_user+0xf8/0x19c
[ 57.597754] sel_write_load+0x178/0xd54
[ 57.597762] vfs_write+0x108/0x6e8
[ 57.597769] ksys_write+0x84/0x140
[ 57.597777] system_call_exception+0x130/0x360
[ 57.597785] system_call_common+0x160/0x2c4
[ 57.597794]
-> #0 (&mm->mmap_lock){++++}-{4:4}:
[ 57.597806] __lock_acquire+0x17cc/0x2330
[ 57.597814] lock_acquire+0x138/0x400
[ 57.597822] __might_fault+0x7c/0xc0
[ 57.597830] filldir64+0xe8/0x390
[ 57.597839] dcache_readdir+0x80/0x2d4
[ 57.597846] iterate_dir+0xd8/0x1d4
[ 57.597855] sys_getdents64+0x88/0x2d4
[ 57.597864] system_call_exception+0x130/0x360
[ 57.597872] system_call_common+0x160/0x2c4
[ 57.597881]
other info that might help us debug this:
[ 57.597888] Chain exists of:
&mm->mmap_lock --> &q->debugfs_mutex --> &sb->s_type->i_mutex_key#3
[ 57.597905] Possible unsafe locking scenario:
[ 57.597911] CPU0 CPU1
[ 57.597917] ---- ----
[ 57.597922] rlock(&sb->s_type->i_mutex_key#3);
[ 57.597932] lock(&q->debugfs_mutex);
[ 57.597940] lock(&sb->s_type->i_mutex_key#3);
[ 57.597950] rlock(&mm->mmap_lock);
[ 57.597958]
*** DEADLOCK ***
[ 57.597965] 2 locks held by ls/4605:
[ 57.597971] #0: c0000000137c12f8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0xcc/0x154
[ 57.597989] #1: c0000018e27c6810 (&sb->s_type->i_mutex_key#3){++++}-{4:4}, at: iterate_dir+0x94/0x1d4
Prevent the above lockdep warning by acquiring ->sysfs_lock before
freezing the queue while storing a queue attribute in queue_attr_store
function. Later, we also found[1] another function __blk_mq_update_nr_
hw_queues where we first freeze queue and then acquire the ->sysfs_lock.
So we've also updated lock ordering in __blk_mq_update_nr_hw_queues
function and ensured that in all code paths we follow the correct lock
ordering i.e. acquire ->sysfs_lock before freezing the queue.
[1] https://lore.kernel.org/all/CAFj5m9Ke8+EHKQBs_Nk6hqd=LGXtk4mUxZUN5==ZcCjnZSBwHw@mail.gmail.com/
Reported-by: kjain@linux.ibm.com
Fixes: af2814149883 ("block: freeze the queue in queue_attr_store")
Tested-by: kjain@linux.ibm.com
Cc: hch@lst.de
Cc: axboe@kernel.dk
Cc: ritesh.list@gmail.com
Cc: ming.lei@redhat.com
Cc: gjoyce@linux.ibm.com
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241210144222.1066229-1-nilay@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Move a statement that occurs in both branches of an if-statement in front
of the if-statement. Fix a typo in a source code comment. No functionality
has been changed.
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Nitesh Shetty <nj.shetty@samsung.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20241212212941.1268662-3-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Registering and unregistering cpuhp callback requires global cpu hotplug lock,
which is used everywhere. Meantime q->sysfs_lock is used in block layer
almost everywhere.
It is easy to trigger lockdep warning[1] by connecting the two locks.
Fix the warning by moving blk-mq's cpuhp callback registering out of
q->sysfs_lock. Add one dedicated global lock for covering registering &
unregistering hctx's cpuhp, and it is safe to do so because hctx is
guaranteed to be live if our request_queue is live.
[1] https://lore.kernel.org/lkml/Z04pz3AlvI4o0Mr8@agluck-desk3/
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Peter Newman <peternewman@google.com>
Cc: Babu Moger <babu.moger@amd.com>
Reported-by: Luck Tony <tony.luck@intel.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20241206111611.978870-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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We need to retrieve 'hctx' from xarray table in the cpuhp callback, so the
callback should be registered after this 'hctx' is added to xarray table.
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Peter Newman <peternewman@google.com>
Cc: Babu Moger <babu.moger@amd.com>
Cc: Luck Tony <tony.luck@intel.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20241206111611.978870-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The rq->part pointer is already NULLified in the memset() call, so - like
for other pointers in rq - don't re-NULLify.
Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20241125100258.4172774-1-john.g.garry@oracle.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Fix an issue detected by the `smatch` tool:
block/blk-mq.c:3314 blk_rq_prep_clone() error: uninitialized
symbol 'bio'.
This patch refactors `blk_rq_prep_clone()` to improve code
readability and ensure safety by addressing potential misuse of
the `bio` variable:
- Move the bio_put(bio); call to the bio_ctr error handling block,
which is the only place where it can be triggered.
- Move the bio variable into the __rq_for_each_bio loop scope.
This change removes the need to set bio to NULL at the loop's
end.
discussion on why bio remains uninitialized:
https://lore.kernel.org/lkml/20241004141037.43277-1-surajsonawane0215@gmail.com
Summary of above discussion:
- I pointed out that `bio` can remain uninitialized if the
allocation with `bio_alloc_clone` fails.
- Keith Busch explained that `bio` is initialized to `NULL` when
`bio_alloc_clone()` fails, preventing uninitialized usage.
- John Garry questioned whether `rq_src->bio` being `NULL` could
leave `bio` uninitialized. Keith clarified that in such cases,
`bio` is not referenced, so it does not need initialization.
- Christoph Hellwig recommended code improvements:
- move the bio_put to the bio_ctr error handling, which is the only
case where it can happen
- move the bio variable into the __rq_for_each_bio scope, which
also removed the need to zero it at the end of the loop
These changes enhance code clarity, address static analysis tool
warnings, and make the function more maintainable.
thread of previous version patch discussion:
https://lore.kernel.org/lkml/20241004100842.9052-1-surajsonawane0215@gmail.com
Signed-off-by: Suraj Sonawane <surajsonawane0215@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241119164412.37609-1-surajsonawane0215@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Add requests to the tail of the list instead of the front so that they
are queued up in submission order.
Remove the re-reordering in blk_mq_dispatch_plug_list, virtio_queue_rqs
and nvme_queue_rqs now that the list is ordered as expected.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241113152050.157179-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Replace the semi-open coded request list helpers with a proper rq_list
type that mirrors the bio_list and has head and tail pointers. Besides
better type safety this actually allows to insert at the tail of the
list, which will be useful soon.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241113152050.157179-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The request ioprio is only initialized from the first attached bio,
so requests without a bio already never set it. Directly use the
bio field instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20241112170050.1612998-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The write_hint is only used for read/write requests, which must have a
bio attached to them. Just use the bio field instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20241112170050.1612998-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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commit f1be1788a32e ("block: model freeze & enter queue as lock for
supporting lockdep") tries to apply lockdep for verifying freeze &
unfreeze. However, the verification is only done the outmost freeze and
unfreeze. This way is actually not correct because q->mq_freeze_depth
still may drop to zero on other task instead of the freeze owner task.
Fix this issue by always verifying the last unfreeze lock on the owner
task context, and make sure both the outmost freeze & unfreeze are
verified in the current task.
Fixes: f1be1788a32e ("block: model freeze & enter queue as lock for supporting lockdep")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241031133723.303835-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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No one use blk_freeze_queue(), so remove it and the obsolete comment.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241031133723.303835-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Recently we got several deadlock report[1][2][3] caused by
blk_mq_freeze_queue and blk_enter_queue().
Turns out the two are just like acquiring read/write lock, so model them
as read/write lock for supporting lockdep:
1) model q->q_usage_counter as two locks(io and queue lock)
- queue lock covers sync with blk_enter_queue()
- io lock covers sync with bio_enter_queue()
2) make the lockdep class/key as per-queue:
- different subsystem has very different lock use pattern, shared lock
class causes false positive easily
- freeze_queue degrades to no lock in case that disk state becomes DEAD
because bio_enter_queue() won't be blocked any more
- freeze_queue degrades to no lock in case that request queue becomes dying
because blk_enter_queue() won't be blocked any more
3) model blk_mq_freeze_queue() as acquire_exclusive & try_lock
- it is exclusive lock, so dependency with blk_enter_queue() is covered
- it is trylock because blk_mq_freeze_queue() are allowed to run
concurrently
4) model blk_enter_queue() & bio_enter_queue() as acquire_read()
- nested blk_enter_queue() are allowed
- dependency with blk_mq_freeze_queue() is covered
- blk_queue_exit() is often called from other contexts(such as irq), and
it can't be annotated as lock_release(), so simply do it in
blk_enter_queue(), this way still covered cases as many as possible
With lockdep support, such kind of reports may be reported asap and
needn't wait until the real deadlock is triggered.
For example, lockdep report can be triggered in the report[3] with this
patch applied.
[1] occasional block layer hang when setting 'echo noop > /sys/block/sda/queue/scheduler'
https://bugzilla.kernel.org/show_bug.cgi?id=219166
[2] del_gendisk() vs blk_queue_enter() race condition
https://lore.kernel.org/linux-block/20241003085610.GK11458@google.com/
[3] queue_freeze & queue_enter deadlock in scsi
https://lore.kernel.org/linux-block/ZxG38G9BuFdBpBHZ@fedora/T/#u
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241025003722.3630252-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Add non_owner variant of start_freeze/unfreeze queue APIs, so that the
caller knows that what they are doing, and we can skip lockdep support
for non_owner variant in per-call level.
Prepare for supporting lockdep for freezing/unfreezing queue.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241025003722.3630252-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Commit a6088845c2bf ("block: kyber: make kyber more friendly with merging")
removed the only blk_mq_flush_busy_ctxs() call from outside the block layer
core. Hence unexport blk_mq_flush_busy_ctxs().
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20241023202850.3469279-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Make sure that the tag_list_lock mutex is not held any longer than
necessary. This change reduces latency if e.g. blk_mq_quiesce_tagset()
is called concurrently from more than one thread. This function is used
by the NVMe core and also by the UFS driver.
Reported-by: Peter Wang <peter.wang@mediatek.com>
Cc: Chao Leng <lengchao@huawei.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 414dd48e882c ("blk-mq: add tagset quiesce interface")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20241022181617.2716173-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Supposing first scenario with a virtio_blk driver.
CPU0 CPU1
blk_mq_try_issue_directly()
__blk_mq_issue_directly()
q->mq_ops->queue_rq()
virtio_queue_rq()
blk_mq_stop_hw_queue()
virtblk_done()
blk_mq_request_bypass_insert() 1) store
blk_mq_start_stopped_hw_queue()
clear_bit(BLK_MQ_S_STOPPED) 3) store
blk_mq_run_hw_queue()
if (!blk_mq_hctx_has_pending()) 4) load
return
blk_mq_sched_dispatch_requests()
blk_mq_run_hw_queue()
if (!blk_mq_hctx_has_pending())
return
blk_mq_sched_dispatch_requests()
if (blk_mq_hctx_stopped()) 2) load
return
__blk_mq_sched_dispatch_requests()
Supposing another scenario.
CPU0 CPU1
blk_mq_requeue_work()
blk_mq_insert_request() 1) store
virtblk_done()
blk_mq_start_stopped_hw_queue()
blk_mq_run_hw_queues() clear_bit(BLK_MQ_S_STOPPED) 3) store
blk_mq_run_hw_queue()
if (!blk_mq_hctx_has_pending()) 4) load
return
blk_mq_sched_dispatch_requests()
if (blk_mq_hctx_stopped()) 2) load
continue
blk_mq_run_hw_queue()
Both scenarios are similar, the full memory barrier should be inserted
between 1) and 2), as well as between 3) and 4) to make sure that either
CPU0 sees BLK_MQ_S_STOPPED is cleared or CPU1 sees dispatch list.
Otherwise, either CPU will not rerun the hardware queue causing
starvation of the request.
The easy way to fix it is to add the essential full memory barrier into
helper of blk_mq_hctx_stopped(). In order to not affect the fast path
(hardware queue is not stopped most of the time), we only insert the
barrier into the slow path. Actually, only slow path needs to care about
missing of dispatching the request to the low-level device driver.
Fixes: 320ae51feed5 ("blk-mq: new multi-queue block IO queueing mechanism")
Cc: stable@vger.kernel.org
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241014092934.53630-4-songmuchun@bytedance.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Supposing the following scenario.
CPU0 CPU1
blk_mq_insert_request() 1) store
blk_mq_unquiesce_queue()
blk_queue_flag_clear() 3) store
blk_mq_run_hw_queues()
blk_mq_run_hw_queue()
if (!blk_mq_hctx_has_pending()) 4) load
return
blk_mq_run_hw_queue()
if (blk_queue_quiesced()) 2) load
return
blk_mq_sched_dispatch_requests()
The full memory barrier should be inserted between 1) and 2), as well as
between 3) and 4) to make sure that either CPU0 sees QUEUE_FLAG_QUIESCED
is cleared or CPU1 sees dispatch list or setting of bitmap of software
queue. Otherwise, either CPU will not rerun the hardware queue causing
starvation.
So the first solution is to 1) add a pair of memory barrier to fix the
problem, another solution is to 2) use hctx->queue->queue_lock to
synchronize QUEUE_FLAG_QUIESCED. Here, we chose 2) to fix it since
memory barrier is not easy to be maintained.
Fixes: f4560ffe8cec ("blk-mq: use QUEUE_FLAG_QUIESCED to quiesce queue")
Cc: stable@vger.kernel.org
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241014092934.53630-3-songmuchun@bytedance.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Supposing the following scenario with a virtio_blk driver.
CPU0 CPU1 CPU2
blk_mq_try_issue_directly()
__blk_mq_issue_directly()
q->mq_ops->queue_rq()
virtio_queue_rq()
blk_mq_stop_hw_queue()
virtblk_done()
blk_mq_try_issue_directly()
if (blk_mq_hctx_stopped())
blk_mq_request_bypass_insert() blk_mq_run_hw_queue()
blk_mq_run_hw_queue() blk_mq_run_hw_queue()
blk_mq_insert_request()
return
After CPU0 has marked the queue as stopped, CPU1 will see the queue is
stopped. But before CPU1 puts the request on the dispatch list, CPU2
receives the interrupt of completion of request, so it will run the
hardware queue and marks the queue as non-stopped. Meanwhile, CPU1 also
runs the same hardware queue. After both CPU1 and CPU2 complete
blk_mq_run_hw_queue(), CPU1 just puts the request to the same hardware
queue and returns. It misses dispatching a request. Fix it by running
the hardware queue explicitly. And blk_mq_request_issue_directly()
should handle a similar situation. Fix it as well.
Fixes: d964f04a8fde ("blk-mq: fix direct issue")
Cc: stable@vger.kernel.org
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20241014092934.53630-2-songmuchun@bytedance.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Applications using the passthrough interfaces for IO want to continue
seeing the disk stats. These requests had been fenced off from this
block layer feature. While the block layer doesn't necessarily know what
a passthrough command does, we do know the data size and direction,
which is enough to account for the command's stats.
Since tracking these has the potential to produce unexpected results,
the passthrough stats are locked behind a new queue flag that needs to
be enabled with the /sys/block/<dev>/queue/iostats_passthrough
attribute.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241007153236.2818562-1-kbusch@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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It's known needed at that point, and it's cleaner to just assign it
there rather than rely on it being reliably set before hitting the
IO accounting. Hence, move it out of blk_mq_rq_time_init(), which is
now only doing the allocation side timing.
While at it, get rid of the '0' time passing to blk_mq_rq_time_init(),
just pass in blk_time_get_ns() for the two cases where 0 is being
explicitly passed in. The rest pass in the previously cached allocation
time.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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A previous commit moved RQF_IO_STAT into blk_account_io_done(), where
it's being set rather than at allocation time. Unfortunately we do check
for that flag in blk_mq_rq_time_init(), and hence setting the
start_time_ns wasn't being done. This lead to unwieldy inflight IO counts
and times, as IO completion accounting would a 0 value rather than the
issue time for it's subtraction math.
Fix this by switching the blk_mq_rq_time_init() check to use the queue
state rather than the request state.
Fixes: b8f762400ae8 ("block: move iostat check into blk_acount_io_start()")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202410062110.512391df-oliver.sang@intel.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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It's now just checking whether or not RQF_IO_STAT is set, so let's get
rid of it and just open-code the specific flag that is being checked.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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If RQF_IO_STAT is set, then accounting is enabled. There's no need to
further gate this on req->part being set or not, RQF_IO_STAT should
never be set if accounting is not being done for this request.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Rather than have blk_do_io_stat() check for both RQF_IO_STAT and whether
the request is a passthrough requests every time, move both of those
checks into blk_account_io_start(). Then blk_do_io_stat() can be reduced
to just checking for RQF_IO_STAT.
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Anuj Gupta <anuj20.g@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Commit 7b815817aa58 ("blk-mq: add helper for checking if one CPU is mapped to specified hctx")
needs to check queue mapping via tag set in hctx's cpuhp handler.
However, q->tag_set may not be setup yet when the cpuhp handler is
enabled, then kernel oops is triggered.
Fix the issue by setup queue tag_set before initializing hctx.
Cc: stable@vger.kernel.org
Reported-and-tested-by: Rick Koch <mr.rickkoch@gmail.com>
Closes: https://lore.kernel.org/linux-block/CANa58eeNDozLaBHKPLxSAhEy__FPfJT_F71W=sEQw49UCrC9PQ@mail.gmail.com
Fixes: 7b815817aa58 ("blk-mq: add helper for checking if one CPU is mapped to specified hctx")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20241014005115.2699642-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Pull more block updates from Jens Axboe:
- Improve blk-integrity segment counting and merging (Keith)
- NVMe pull request via Keith:
- Multipath fixes (Hannes)
- Sysfs attribute list NULL terminate fix (Shin'ichiro)
- Remove problematic read-back (Keith)
- Fix for a regression with the IO scheduler switching freezing from
6.11 (Damien)
- Use a raw spinlock for sbitmap, as it may get called from preempt
disabled context (Ming)
- Cleanup for bd_claiming waiting, using var_waitqueue() rather than
the bit waitqueues, as that more accurately describes that it does
(Neil)
- Various cleanups (Kanchan, Qiu-ji, David)
* tag 'for-6.12/block-20240925' of git://git.kernel.dk/linux:
nvme: remove CC register read-back during enabling
nvme: null terminate nvme_tls_attrs
nvme-multipath: avoid hang on inaccessible namespaces
nvme-multipath: system fails to create generic nvme device
lib/sbitmap: define swap_lock as raw_spinlock_t
block: Remove unused blk_limits_io_{min,opt}
drbd: Fix atomicity violation in drbd_uuid_set_bm()
block: Fix elv_iosched_local_module handling of "none" scheduler
block: remove bogus union
block: change wait on bd_claiming to use a var_waitqueue
blk-integrity: improved sg segment mapping
block: unexport blk_rq_count_integrity_sg
nvme-rdma: use request to get integrity segments
scsi: use request to get integrity segments
block: provide a request helper for user integrity segments
blk-integrity: consider entire bio list for merging
blk-integrity: properly account for segments
blk-mq: set the nr_integrity_segments from bio
blk-mq: unconditional nr_integrity_segments
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull irq updates from Thomas Gleixner:
"Core:
- Remove a global lock in the affinity setting code
The lock protects a cpumask for intermediate results and the lock
causes a bottleneck on simultaneous start of multiple virtual
machines. Replace the lock and the static cpumask with a per CPU
cpumask which is nicely serialized by raw spinlock held when
executing this code.
- Provide support for giving a suffix to interrupt domain names.
That's required to support devices with subfunctions so that the
domain names are distinct even if they originate from the same
device node.
- The usual set of cleanups and enhancements all over the place
Drivers:
- Support for longarch AVEC interrupt chip
- Refurbishment of the Armada driver so it can be extended for new
variants.
- The usual set of cleanups and enhancements all over the place"
* tag 'irq-core-2024-09-16' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (73 commits)
genirq: Use cpumask_intersects()
genirq/cpuhotplug: Use cpumask_intersects()
irqchip/apple-aic: Only access system registers on SoCs which provide them
irqchip/apple-aic: Add a new "Global fast IPIs only" feature level
irqchip/apple-aic: Skip unnecessary enabling of use_fast_ipi
dt-bindings: apple,aic: Document A7-A11 compatibles
irqdomain: Use IS_ERR_OR_NULL() in irq_domain_trim_hierarchy()
genirq/msi: Use kmemdup_array() instead of kmemdup()
genirq/proc: Change the return value for set affinity permission error
genirq/proc: Use irq_move_pending() in show_irq_affinity()
genirq/proc: Correctly set file permissions for affinity control files
genirq: Get rid of global lock in irq_do_set_affinity()
genirq: Fix typo in struct comment
irqchip/loongarch-avec: Add AVEC irqchip support
irqchip/loongson-pch-msi: Prepare get_pch_msi_handle() for AVECINTC
irqchip/loongson-eiointc: Rename CPUHP_AP_IRQ_LOONGARCH_STARTING
LoongArch: Architectural preparation for AVEC irqchip
LoongArch: Move irqchip function prototypes to irq-loongson.h
irqchip/loongson-pch-msi: Switch to MSI parent domains
softirq: Remove unused 'action' parameter from action callback
...
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This value is used for merging considerations, so it needs to be
accurate.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20240913182854.2445457-3-kbusch@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Always defining the field will make using it easier and less error prone
in future patches.
There shouldn't be any downside to this: the field fits in what would
otherwise be a 2-byte hole, so we're not saving space by conditionally
leaving it out.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20240913182854.2445457-2-kbusch@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The single-queue optimized list flush doesn't have an unplug trace event
to pair with the plug event. Add one.
In the unlikely event an error occurs and falls back to the less
optimized plug flush path, it's possible a 2nd unplug trace event will
be logged, but it will show the remainig count that weren't previously
handled.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20240906194540.3719642-1-kbusch@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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The current setup with bio_may_exceed_limit and __bio_split_to_limits
is a bit of a mess.
Change it so that __bio_split_to_limits does all the work and is just
a variant of bio_split_to_limits that returns nr_segs. This is done
by inlining it and instead have the various bio_split_* helpers directly
submit the potentially split bios.
To support btrfs, the rw version has a lower level helper split out
that just returns the offset to split. This turns out to nicely clean
up the btrfs flow as well.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: David Sterba <dsterba@suse.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Tested-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Hans Holmberg <hans.holmberg@wdc.com>
Link: https://lore.kernel.org/r/20240826173820.1690925-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
|
