linux-stable.git/block/elevator.c, branch v6.14

block: force noio scope in blk_mq_freeze_queue

2025-01-31T14:20:08+00:00

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 
Link: https://lore.kernel.org/r/20250131120352.1315351-2-hch@lst.de
Signed-off-by: Jens Axboe

block: remove BLK_MQ_F_NO_SCHED

2025-01-06T14:37:41+00:00

The only queues that really can't support a scheduler are those that
do not have a gendisk associated with them, and thus can't be used for
non-passthrough commands.  In addition to those null_blk can optionally
set the flag, which is a bad odd.  Replace the null_blk usage with
BLK_MQ_F_NO_SCHED_BY_DEFAULT to keep the expected semantics and then
remove BLK_MQ_F_NO_SCHED as the non-disk queues never call into
elevator_init_mq or blk_register_queue which adds the sysfs attributes.

Signed-off-by: Christoph Hellwig 
Link: https://lore.kernel.org/r/20250106083531.799976-4-hch@lst.de
Signed-off-by: Jens Axboe

elevator: Enable const sysfs attributes

2025-01-02T20:20:29+00:00

The elevator core does not need to modify the sysfs attributes added by
the elevators. Reflect this in the types, so the attributes can be moved
into read-only memory.

Signed-off-by: Thomas Weißschuh 
Link: https://lore.kernel.org/r/20250102-sysfs-const-attr-elevator-v1-1-9837d2058c60@weissschuh.net
Signed-off-by: Jens Axboe

block: don't verify queue freeze manually in elevator_init_mq()

2024-12-23T15:17:22+00:00

Now blk_freeze_queue_start() can track disk state automatically, and
it isn't necessary to verify queue freeze manually in elevator_init_mq()
any more.

Signed-off-by: Ming Lei 
Link: https://lore.kernel.org/r/20241127135133.3952153-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe

block: track disk DEAD state automatically for modeling queue freeze lockdep

2024-12-23T15:17:22+00:00

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 
Link: https://lore.kernel.org/r/20241127135133.3952153-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe

block: don't verify IO lock for freeze/unfreeze in elevator_init_mq()

2024-11-07T23:27:22+00:00

elevator_init_mq() is only called at the entry of add_disk_fwnode() when
disk IO isn't allowed yet.

So not verify io lock(q->io_lockdep_map) for freeze & unfreeze in
elevator_init_mq().

Reported-by: Marek Szyprowski 
Reported-by: Lai Yi 
Fixes: f1be1788a32e ("block: model freeze & enter queue as lock for supporting lockdep")
Signed-off-by: Ming Lei 
Link: https://lore.kernel.org/r/20241031133723.303835-5-ming.lei@redhat.com
Signed-off-by: Jens Axboe

block: return void from the queue_sysfs_entry load_module method

2024-10-22T14:16:22+00:00

Requesting a module either succeeds or does nothing, return an error from
this method does not make sense.

Also move the load_module after the store method in the struct
declaration to keep the important show and store methods together.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Damien Le Moal 
Reviewed-by: Andreas Hindborg 
Link: https://lore.kernel.org/r/20241008050841.104602-1-hch@lst.de
Signed-off-by: Jens Axboe

elevator: Remove argument from elevator_find_get

2024-10-11T17:11:09+00:00

Commit e4eb37cc0f3ed ("block: Remove elevator required features")
removed the usage of `struct request_queue` from elevator_find_get(),
but didn't removed the argument.

Remove the "struct request_queue *q" argument from elevator_find_get()
given it is useless.

Fixes: e4eb37cc0f3e ("block: Remove elevator required features")
Signed-off-by: Breno Leitao 
Link: https://lore.kernel.org/r/20241011155615.3361143-1-leitao@debian.org
Signed-off-by: Jens Axboe

elevator: do not request_module if elevator exists

2024-10-11T17:10:52+00:00

Whenever an I/O elevator is changed, the system attempts to load a
module for the new elevator. This occurs regardless of whether the
elevator is already loaded or built directly into the kernel. This
behavior introduces unnecessary overhead and potential issues.

This makes the operation slower, and more error-prone. For instance,
making the problem fixed by [1] visible for users that doesn't even rely
on modules being available through modules.

Do not try to load the ioscheduler if it is already visible.

This change brings two main benefits: it improves the performance of
elevator changes, and it reduces the likelihood of errors occurring
during this process.

[1] Commit e3accac1a976 ("block: Fix elv_iosched_local_module handling of "none" scheduler")

Fixes: 734e1a860312 ("block: Prevent deadlocks when switching elevators")
Signed-off-by: Breno Leitao 
Link: https://lore.kernel.org/r/20241011170122.3880087-1-leitao@debian.org
Signed-off-by: Jens Axboe

block: Fix elevator_get_default() checking for NULL q->tag_set

2024-10-07T20:24:36+00:00

elevator_get_default() and elv_support_iosched() both check for whether
or not q->tag_set is non-NULL, however it's not possible for them to be
NULL. This messes up some static checkers, as the checking of tag_set
isn't consistent.

Remove the checks, which both simplifies the logic and avoids checker
errors.

Signed-off-by: SurajSonawane2415 
Link: https://lore.kernel.org/r/20241007111416.13814-1-surajsonawane0215@gmail.com
Signed-off-by: Jens Axboe