linux-stable.git/include/linux/blk-mq.h, branch v5.7.1

blk-mq: Replace zero-length array with flexible-array member

2020-04-18T20:44:54+00:00

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva

block: add a blk_mq_init_queue_data helper

2020-03-27T16:23:43+00:00

This allows a driver to pass a queuedata member before ->init_hctx is
called.  null_blk currently open codes this logic, but I'd rather have
it in the core to ease future maintainance.

Reviewed-by: Johannes Thumshirn 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

blk-mq: Fix a comment in include/linux/blk-mq.h

2020-03-10T13:09:59+00:00

The 'hctx_list' member of struct blk_mq_hw_ctx is not a list head but
instead an entry in q->unused_hctx_list. Fix the comment above this
struct member.

Fixes: d386732bc142 ("blk-mq: fill header with kernel-doc")
Signed-off-by: Bart Van Assche 
Reviewed-by: Chaitanya Kulkarni 
Cc: André Almeida 
Signed-off-by: Jens Axboe

blk-mq: Delete blk_mq_has_free_tags() and blk_mq_can_queue()

2019-11-13T19:50:38+00:00

These functions are not referenced, so delete them.

Signed-off-by: John Garry 
Signed-off-by: Jens Axboe

blk-mq: Make blk_mq_run_hw_queue() return void

2019-11-01T14:42:41+00:00

Since commit 97889f9ac24f ("blk-mq: remove synchronize_rcu() from
blk_mq_del_queue_tag_set()"), the return value of blk_mq_run_hw_queue()
is never checked, so make it return void, which very marginally simplifies
the code.

Reviewed-by: Bob Liu 
Signed-off-by: John Garry 
Signed-off-by: Jens Axboe

blk-mq: fill header with kernel-doc

2019-10-25T20:28:10+00:00

Insert documentation for structs, enums and functions at header file.
Format existing and new comments at struct blk_mq_ops as
kernel-doc comments.

Reviewed-by: Bart Van Assche 
Signed-off-by: André Almeida 
Signed-off-by: Jens Axboe

blk-mq: Inline status checkers

2019-10-07T14:31:59+00:00

blk_mq_request_completed() and blk_mq_request_started() are
short, inline it.

Signed-off-by: Pavel Begunkov 
Signed-off-by: Jens Axboe

block: Document all members of blk_mq_tag_set and bkl_mq_queue_map

2019-10-07T14:31:59+00:00

The meaning of several member variables of these two data structures is
nontrivial. Hence document all member variables using the kernel-doc
syntax.

Cc: Christoph Hellwig 
Cc: Ming Lei 
Cc: Hannes Reinecke 
Cc: Johannes Thumshirn 
Signed-off-by: Bart Van Assche 
Signed-off-by: Jens Axboe

block: Delay default elevator initialization

2019-09-06T01:52:34+00:00

When elevator_init_mq() is called from blk_mq_init_allocated_queue(),
the only information known about the device is the number of hardware
queues as the block device scan by the device driver is not completed
yet for most drivers. The device type and elevator required features
are not set yet, preventing to correctly select the default elevator
most suitable for the device.

This currently affects all multi-queue zoned block devices which default
to the "none" elevator instead of the required "mq-deadline" elevator.
These drives currently include host-managed SMR disks connected to a
smartpqi HBA and null_blk block devices with zoned mode enabled.
Upcoming NVMe Zoned Namespace devices will also be affected.

Fix this by adding the boolean elevator_init argument to
blk_mq_init_allocated_queue() to control the execution of
elevator_init_mq(). Two cases exist:
1) elevator_init = false is used for calls to
   blk_mq_init_allocated_queue() within blk_mq_init_queue(). In this
   case, a call to elevator_init_mq() is added to __device_add_disk(),
   resulting in the delayed initialization of the queue elevator
   after the device driver finished probing the device information. This
   effectively allows elevator_init_mq() access to more information
   about the device.
2) elevator_init = true preserves the current behavior of initializing
   the elevator directly from blk_mq_init_allocated_queue(). This case
   is used for the special request based DM devices where the device
   gendisk is created before the queue initialization and device
   information (e.g. queue limits) is already known when the queue
   initialization is executed.

Additionally, to make sure that the elevator initialization is never
done while requests are in-flight (there should be none when the device
driver calls device_add_disk()), freeze and quiesce the device request
queue before calling blk_mq_init_sched() in elevator_init_mq().

Reviewed-by: Ming Lei 
Signed-off-by: Damien Le Moal 
Signed-off-by: Jens Axboe

block: Remove blk_mq_register_dev()

2019-08-27T16:40:19+00:00

This function has no callers. Hence remove it.

Cc: Christoph Hellwig 
Cc: Ming Lei 
Cc: Hannes Reinecke 
Signed-off-by: Bart Van Assche 
Signed-off-by: Jens Axboe