| Message ID | 20200623220311.8033-2-mcgrof@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: kdocify the request_queue | expand |
On 2020/06/24 7:03, Luis Chamberlain wrote: > We start off with an initial description of the request_queue data > structure, followed by describing the purpose of the debugfs_mutex > debugfs_dir, and blk_trace. > > Suggested-by: Bart Van Assche <bvanassche@acm.org> > Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> > --- > include/linux/blkdev.h | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index 70461b347169..ea319c2b0593 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -394,6 +394,26 @@ static inline int blkdev_zone_mgmt_ioctl(struct block_device *bdev, > > #endif /* CONFIG_BLK_DEV_ZONED */ > > +/** > + * struct request_queue - block device driver request queue > + * @debugfs_mutex: used to protect access to the @debugfs_dir > + * @blk_trace: used by blktrace to keep track of setup / tracing > + * @debugfs_dir: directory created to place debugfs information. This is always > + * created for make_request and request-based block drivers upon > + * initialization. blktrace requires for this directory to be created, s/requires for/requires/ (may be, not sure of my English grammar on this one :)) > + * and so it will be created on demand if its block driver type does not > + * create it opon initialization. s/opon/upon/ > + * > + * The request_queue is used to manage incoming block layer device driver > + * requests. We have three main type of block driver types which end up making We have three main types of block drivers which... > + * use of the request_queue: > + * > + * o make_request block drivers (multiqueue) > + * o request-based block drivers Isn't this second one BIO based drivers, like device-mapper BIO targets ? > + * o custom solutions such as scsi-generic The SG driver does not create a request queue, it uses the one of the scsi device created by the scsi stack. Is this what you mean here ? Saying scsi-generic kind of implies sg driver. > + * > + * All partitions share the same request_queue data structure. > + */ > struct request_queue { > struct request *last_merge; > struct elevator_queue *elevator; >
On 24/06/2020 00:04, Luis Chamberlain wrote:
> + * o make_request block drivers (multiqueue)
I don't think the differentiation between singlequeue and
multiqueue is usefull, given that the single queue block layer
is gone for quite some time now.
On 2020-06-23 15:03, Luis Chamberlain wrote: > +/** > + * struct request_queue - block device driver request queue Since request queues are used as a communication channel between the block layer core and block drivers and since the block layer core creates request queues, I propose to leave out the word "driver". > + * @debugfs_mutex: used to protect access to the @debugfs_dir > + * @blk_trace: used by blktrace to keep track of setup / tracing > + * @debugfs_dir: directory created to place debugfs information. This is always > + * created for make_request and request-based block drivers upon > + * initialization. blktrace requires for this directory to be created, > + * and so it will be created on demand if its block driver type does not > + * create it opon initialization. > + * > + * The request_queue is used to manage incoming block layer device driver > + * requests. We have three main type of block driver types which end up making > + * use of the request_queue: "incoming" is correct from the perspective of the block driver but not from the perspective of the block layer core. How about describing request queues as a communication channel between the block layer core and block drivers? Thanks, Bart.
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 70461b347169..ea319c2b0593 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -394,6 +394,26 @@ static inline int blkdev_zone_mgmt_ioctl(struct block_device *bdev, #endif /* CONFIG_BLK_DEV_ZONED */ +/** + * struct request_queue - block device driver request queue + * @debugfs_mutex: used to protect access to the @debugfs_dir + * @blk_trace: used by blktrace to keep track of setup / tracing + * @debugfs_dir: directory created to place debugfs information. This is always + * created for make_request and request-based block drivers upon + * initialization. blktrace requires for this directory to be created, + * and so it will be created on demand if its block driver type does not + * create it opon initialization. + * + * The request_queue is used to manage incoming block layer device driver + * requests. We have three main type of block driver types which end up making + * use of the request_queue: + * + * o make_request block drivers (multiqueue) + * o request-based block drivers + * o custom solutions such as scsi-generic + * + * All partitions share the same request_queue data structure. + */ struct request_queue { struct request *last_merge; struct elevator_queue *elevator;
We start off with an initial description of the request_queue data structure, followed by describing the purpose of the debugfs_mutex debugfs_dir, and blk_trace. Suggested-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> --- include/linux/blkdev.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)