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Date: Wed, 24 Jun 2020 00:46:38 +0000
From: Damien Le Moal <Damien.LeMoal@....com>
To: Luis Chamberlain <mcgrof@...nel.org>,
"axboe@...nel.dk" <axboe@...nel.dk>,
"bvanassche@....org" <bvanassche@....org>,
"ming.lei@...hat.com" <ming.lei@...hat.com>,
"martin.petersen@...cle.com" <martin.petersen@...cle.com>,
"satyat@...gle.com" <satyat@...gle.com>
CC: "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] block: move request_queue member docs to kdoc
On 2020/06/24 7:03, Luis Chamberlain wrote:
> Now that we have a template, expand on the kdoc form for
> the request_queue data structure with documentation from
> the rest of the members, *only* for information we already
> had.
>
> This does not add any new documentation. This just shifts
> documentation to kdoc form.
>
> Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
> ---
> include/linux/blkdev.h | 139 ++++++++++++-----------------------------
> 1 file changed, 40 insertions(+), 99 deletions(-)
>
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index ea319c2b0593..d30bfef893b9 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -396,8 +396,38 @@ static inline int blkdev_zone_mgmt_ioctl(struct block_device *bdev,
>
> /**
> * struct request_queue - block device driver request queue
> + * @queue_ctx: software queue context
> + * @queue_hw_ctx: hw dispatch queues
> + * @queuedata: the queue owner gets to use this for whatever they like.
> + * ll_rw_blk doesn't touch it.
> + * @queue_flags: various queue flags, see %QUEUE_* below
> + * @pm_only: Number of contexts that have called blk_set_pm_only(). If this
> + * counter is above zero then only %RQF_PM and %RQF_PREEMPT requests are
> + * processed.
> + * @id: ida allocated id for this queue. Used to index queues from ioctx.
> + * @bounce_gfp: queue needs bounce pages for pages above this limit
> + * @kobj: queue kobject
> + * @mq_kobj: mq queue kobject
> + * @nr_requests: maximum number of of requests
> + * @ksm: Inline crypto capabilities
> + * @nr_zones:
Above line is not needed, no ?
> + * @nr_zones: total number of zones of the device. This is always 0 for regular
> + * block devices.
May be: "total number of zones for a zoned block device. This is..."
> + * @conv_zones_bitmap: bitmap of nr_zones bits which indicates if a zone
> + * is conventional (bit set) or sequential (bit clear).
> + * @seq_zones_wlock: bitmap of nr_zones bits which indicates if a zone
> + * is write locked, that is, if a write request targeting the zone was
> + * dispatched.
> + * @debugfs_mutex: used to protect access to the @ebugfs_dir
> * @debugfs_mutex: used to protect access to the @debugfs_dir
> * @blk_trace: used by blktrace to keep track of setup / tracing
> + * @fq: for flush operations
> + * @td: throttle data
> + * @unused_hctx_list: list used for reusing dead hctx instance in case of
> + * updating nr_hw_queues.
> + * @unused_hctx_lock: used to protect the @unused_hctx_list
> + * @mq_freeze_lock: protects concurrent access to q_usage_counter by
> + * percpu_ref_kill() and percpu_ref_reinit().
> * @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,
> @@ -413,67 +443,35 @@ static inline int blkdev_zone_mgmt_ioctl(struct block_device *bdev,
> * o custom solutions such as scsi-generic
> *
> * All partitions share the same request_queue data structure.
> + *
> + * Zoned block device dispatch control is managed by the fields @nr_zones,
> + * @conv_zones_bitmap and @seq_zones_wlock. These fields are fields are> + * initialized by the low level device driver (e.g. scsi/sd.c). Stacking
> + * drivers (device mappers) may or may not initialize these fields.
> + * Reads of this information must be protected with blk_queue_enter() /
> + * blk_queue_exit(). Modifying this information is only allowed while
> + * no requests are being processed. See also blk_mq_freeze_queue() and
> + * blk_mq_unfreeze_queue().
Ooops... This is outdated... This should be:
* Dispatch of write commands to zoned block devices is controlled using the
* fields @nr_zones, @conv_zones_bitmap and @seq_zones_wlock. These fields are
* initialized using the blk_revalidate_disk_zones() function from the level
* request based device drivers (e.g. scsi/sd.c). BIO based drivers, if needed,
* can initialize these fields directly. Accesses to these fields must be
* protected with blk_queue_enter() / blk_queue_exit(). Modification of the
* @nr_zones field and reallocation of the @conv_zones_bitmap and
* @seq_zones_wlock bitmaps is only allowed while no requests are being
* processed. See also blk_mq_freeze_queue() and blk_mq_unfreeze_queue().
> */
> struct request_queue {
> struct request *last_merge;
> struct elevator_queue *elevator;
> -
> struct blk_queue_stats *stats;
> struct rq_qos *rq_qos;
> -
> make_request_fn *make_request_fn;
> -
> const struct blk_mq_ops *mq_ops;
> -
> - /* sw queues */
> struct blk_mq_ctx __percpu *queue_ctx;
> -
> unsigned int queue_depth;
> -
> - /* hw dispatch queues */
> struct blk_mq_hw_ctx **queue_hw_ctx;
> unsigned int nr_hw_queues;
> -
> struct backing_dev_info *backing_dev_info;
> -
> - /*
> - * The queue owner gets to use this for whatever they like.
> - * ll_rw_blk doesn't touch it.
> - */
> void *queuedata;
> -
> - /*
> - * various queue flags, see QUEUE_* below
> - */
> unsigned long queue_flags;
> - /*
> - * Number of contexts that have called blk_set_pm_only(). If this
> - * counter is above zero then only RQF_PM and RQF_PREEMPT requests are
> - * processed.
> - */
> atomic_t pm_only;
> -
> - /*
> - * ida allocated id for this queue. Used to index queues from
> - * ioctx.
> - */
> int id;
> -
> - /*
> - * queue needs bounce pages for pages above this limit
> - */
> gfp_t bounce_gfp;
> -
> spinlock_t queue_lock;
> -
> - /*
> - * queue kobject
> - */
> struct kobject kobj;
> -
> - /*
> - * mq queue kobject
> - */
> struct kobject *mq_kobj;
>
> #ifdef CONFIG_BLK_DEV_INTEGRITY
> @@ -485,66 +483,32 @@ struct request_queue {
> int rpm_status;
> unsigned int nr_pending;
> #endif
> -
> - /*
> - * queue settings
> - */
> - unsigned long nr_requests; /* Max # of requests */
> -
> + unsigned long nr_requests;
> unsigned int dma_pad_mask;
> unsigned int dma_alignment;
> -
> #ifdef CONFIG_BLK_INLINE_ENCRYPTION
> - /* Inline crypto capabilities */
> struct blk_keyslot_manager *ksm;
> #endif
> -
> unsigned int rq_timeout;
> int poll_nsec;
> -
> struct blk_stat_callback *poll_cb;
> struct blk_rq_stat poll_stat[BLK_MQ_POLL_STATS_BKTS];
> -
> struct timer_list timeout;
> struct work_struct timeout_work;
> -
> struct list_head icq_list;
> #ifdef CONFIG_BLK_CGROUP
> DECLARE_BITMAP (blkcg_pols, BLKCG_MAX_POLS);
> struct blkcg_gq *root_blkg;
> struct list_head blkg_list;
> #endif
> -
> struct queue_limits limits;
> -
> unsigned int required_elevator_features;
> -
> #ifdef CONFIG_BLK_DEV_ZONED
> - /*
> - * Zoned block device information for request dispatch control.
> - * nr_zones is the total number of zones of the device. This is always
> - * 0 for regular block devices. conv_zones_bitmap is a bitmap of nr_zones
> - * bits which indicates if a zone is conventional (bit set) or
> - * sequential (bit clear). seq_zones_wlock is a bitmap of nr_zones
> - * bits which indicates if a zone is write locked, that is, if a write
> - * request targeting the zone was dispatched. All three fields are
> - * initialized by the low level device driver (e.g. scsi/sd.c).
> - * Stacking drivers (device mappers) may or may not initialize
> - * these fields.
> - *
> - * Reads of this information must be protected with blk_queue_enter() /
> - * blk_queue_exit(). Modifying this information is only allowed while
> - * no requests are being processed. See also blk_mq_freeze_queue() and
> - * blk_mq_unfreeze_queue().
> - */
> unsigned int nr_zones;
> unsigned long *conv_zones_bitmap;
> unsigned long *seq_zones_wlock;
> #endif /* CONFIG_BLK_DEV_ZONED */
>
> - /*
> - * sg stuff
> - */
> unsigned int sg_timeout;
> unsigned int sg_reserved_size;
> int node;
> @@ -552,59 +516,36 @@ struct request_queue {
> #ifdef CONFIG_BLK_DEV_IO_TRACE
> struct blk_trace __rcu *blk_trace;
> #endif
> - /*
> - * for flush operations
> - */
> struct blk_flush_queue *fq;
> -
> struct list_head requeue_list;
> spinlock_t requeue_lock;
> struct delayed_work requeue_work;
> -
> struct mutex sysfs_lock;
> struct mutex sysfs_dir_lock;
> -
> - /*
> - * for reusing dead hctx instance in case of updating
> - * nr_hw_queues
> - */
> struct list_head unused_hctx_list;
> spinlock_t unused_hctx_lock;
> -
> int mq_freeze_depth;
> -
> #if defined(CONFIG_BLK_DEV_BSG)
> struct bsg_class_device bsg_dev;
> #endif
>
> #ifdef CONFIG_BLK_DEV_THROTTLING
> - /* Throttle data */
> struct throtl_data *td;
> #endif
> struct rcu_head rcu_head;
> wait_queue_head_t mq_freeze_wq;
> - /*
> - * Protect concurrent access to q_usage_counter by
> - * percpu_ref_kill() and percpu_ref_reinit().
> - */
> struct mutex mq_freeze_lock;
> struct percpu_ref q_usage_counter;
> -
> struct blk_mq_tag_set *tag_set;
> struct list_head tag_set_list;
> struct bio_set bio_split;
> -
> struct dentry *debugfs_dir;
> -
> #ifdef CONFIG_BLK_DEBUG_FS
> struct dentry *sched_debugfs_dir;
> struct dentry *rqos_debugfs_dir;
> #endif
> -
> bool mq_sysfs_init_done;
> -
> size_t cmd_size;
> -
> #define BLK_MAX_WRITE_HINTS 5
> u64 write_hints[BLK_MAX_WRITE_HINTS];
> };
>
--
Damien Le Moal
Western Digital Research
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