OSCL-LXR linux-6.0.1/​drivers/​block/​ublk_drv.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Userspace block device - block device which IO is handled from userspace
  *
  * Take full use of io_uring passthrough command for communicating with
  * ublk userspace daemon(ublksrvd) for handling basic IO request.
  *
  * Copyright 2022 Ming Lei <ming.lei@redhat.com>
  *
  * (part of code stolen from loop.c)
  */
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/sched.h>
 #include <linux/fs.h>
 #include <linux/pagemap.h>
 #include <linux/file.h>
 #include <linux/stat.h>
 #include <linux/errno.h>
 #include <linux/major.h>
 #include <linux/wait.h>
 #include <linux/blkdev.h>
 #include <linux/init.h>
 #include <linux/swap.h>
 #include <linux/slab.h>
 #include <linux/compat.h>
 #include <linux/mutex.h>
 #include <linux/writeback.h>
 #include <linux/completion.h>
 #include <linux/highmem.h>
 #include <linux/sysfs.h>
 #include <linux/miscdevice.h>
 #include <linux/falloc.h>
 #include <linux/uio.h>
 #include <linux/ioprio.h>
 #include <linux/sched/mm.h>
 #include <linux/uaccess.h>
 #include <linux/cdev.h>
 #include <linux/io_uring.h>
 #include <linux/blk-mq.h>
 #include <linux/delay.h>
 #include <linux/mm.h>
 #include <asm/page.h>
 #include <linux/task_work.h>
 #include <uapi/linux/ublk_cmd.h>
 
 #define UBLK_MINORS     (1U << MINORBITS)
 
 /* All UBLK_F_* have to be included into UBLK_F_ALL */
 #define UBLK_F_ALL (UBLK_F_SUPPORT_ZERO_COPY \
         | UBLK_F_URING_CMD_COMP_IN_TASK \
         | UBLK_F_NEED_GET_DATA)
 
 /* All UBLK_PARAM_TYPE_* should be included here */
 #define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD)
 
 struct ublk_rq_data {
     struct callback_head work;
 };
 
 struct ublk_uring_cmd_pdu {
     struct request *req;
 };
 
 /*
  * io command is active: sqe cmd is received, and its cqe isn't done
  *
  * If the flag is set, the io command is owned by ublk driver, and waited
  * for incoming blk-mq request from the ublk block device.
  *
  * If the flag is cleared, the io command will be completed, and owned by
  * ublk server.
  */
 #define UBLK_IO_FLAG_ACTIVE 0x01
 
 /*
  * IO command is completed via cqe, and it is being handled by ublksrv, and
  * not committed yet
  *
  * Basically exclusively with UBLK_IO_FLAG_ACTIVE, so can be served for
  * cross verification
  */
 #define UBLK_IO_FLAG_OWNED_BY_SRV 0x02
 
 /*
  * IO command is aborted, so this flag is set in case of
  * !UBLK_IO_FLAG_ACTIVE.
  *
  * After this flag is observed, any pending or new incoming request
  * associated with this io command will be failed immediately
  */
 #define UBLK_IO_FLAG_ABORTED 0x04
 
 /*
  * UBLK_IO_FLAG_NEED_GET_DATA is set because IO command requires
  * get data buffer address from ublksrv.
  *
  * Then, bio data could be copied into this data buffer for a WRITE request
  * after the IO command is issued again and UBLK_IO_FLAG_NEED_GET_DATA is unset.
  */
 #define UBLK_IO_FLAG_NEED_GET_DATA 0x08
 
 struct ublk_io {
     /* userspace buffer address from io cmd */
     __u64   addr;
     unsigned int flags;
     int res;
 
     struct io_uring_cmd *cmd;
 };
 
 struct ublk_queue {
     int q_id;
     int q_depth;
 
     unsigned long flags;
     struct task_struct  *ubq_daemon;
     char *io_cmd_buf;
 
     unsigned long io_addr;  /* mapped vm address */
     unsigned int max_io_sz;
     bool abort_work_pending;
     unsigned short nr_io_ready; /* how many ios setup */
     struct ublk_device *dev;
     struct ublk_io ios[0];
 };
 
 #define UBLK_DAEMON_MONITOR_PERIOD  (5 * HZ)
 
 struct ublk_device {
     struct gendisk      *ub_disk;
 
     char    *__queues;
 
     unsigned short  queue_size;
     struct ublksrv_ctrl_dev_info    dev_info;
 
     struct blk_mq_tag_set   tag_set;
 
     struct cdev     cdev;
     struct device       cdev_dev;
 
 #define UB_STATE_OPEN       0
 #define UB_STATE_USED       1
     unsigned long       state;
     int         ub_number;
 
     struct mutex        mutex;
 
     spinlock_t      mm_lock;
     struct mm_struct    *mm;
 
     struct ublk_params  params;
 
     struct completion   completion;
     unsigned int        nr_queues_ready;
     atomic_t        nr_aborted_queues;
 
     /*
      * Our ubq->daemon may be killed without any notification, so
      * monitor each queue's daemon periodically
      */
     struct delayed_work monitor_work;
     struct work_struct  stop_work;
 };
 
 /* header of ublk_params */
 struct ublk_params_header {
     __u32   len;
     __u32   types;
 };
 
 static dev_t ublk_chr_devt;
 static struct class *ublk_chr_class;
 
 static DEFINE_IDR(ublk_index_idr);
 static DEFINE_SPINLOCK(ublk_idr_lock);
 static wait_queue_head_t ublk_idr_wq;   /* wait until one idr is freed */
 
 static DEFINE_MUTEX(ublk_ctl_mutex);
 
 static struct miscdevice ublk_misc;
 
 static void ublk_dev_param_basic_apply(struct ublk_device *ub)
 {
     struct request_queue *q = ub->ub_disk->queue;
     const struct ublk_param_basic *p = &ub->params.basic;
 
     blk_queue_logical_block_size(q, 1 << p->logical_bs_shift);
     blk_queue_physical_block_size(q, 1 << p->physical_bs_shift);
     blk_queue_io_min(q, 1 << p->io_min_shift);
     blk_queue_io_opt(q, 1 << p->io_opt_shift);
 
     blk_queue_write_cache(q, p->attrs & UBLK_ATTR_VOLATILE_CACHE,
             p->attrs & UBLK_ATTR_FUA);
     if (p->attrs & UBLK_ATTR_ROTATIONAL)
         blk_queue_flag_clear(QUEUE_FLAG_NONROT, q);
     else
         blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
 
     blk_queue_max_hw_sectors(q, p->max_sectors);
     blk_queue_chunk_sectors(q, p->chunk_sectors);
     blk_queue_virt_boundary(q, p->virt_boundary_mask);
 
     if (p->attrs & UBLK_ATTR_READ_ONLY)
         set_disk_ro(ub->ub_disk, true);
 
     set_capacity(ub->ub_disk, p->dev_sectors);
 }
 
 static void ublk_dev_param_discard_apply(struct ublk_device *ub)
 {
     struct request_queue *q = ub->ub_disk->queue;
     const struct ublk_param_discard *p = &ub->params.discard;
 
     q->limits.discard_alignment = p->discard_alignment;
     q->limits.discard_granularity = p->discard_granularity;
     blk_queue_max_discard_sectors(q, p->max_discard_sectors);
     blk_queue_max_write_zeroes_sectors(q,
             p->max_write_zeroes_sectors);
     blk_queue_max_discard_segments(q, p->max_discard_segments);
 }
 
 static int ublk_validate_params(const struct ublk_device *ub)
 {
     /* basic param is the only one which must be set */
     if (ub->params.types & UBLK_PARAM_TYPE_BASIC) {
         const struct ublk_param_basic *p = &ub->params.basic;
 
         if (p->logical_bs_shift > PAGE_SHIFT)
             return -EINVAL;
 
         if (p->logical_bs_shift > p->physical_bs_shift)
             return -EINVAL;
 
         if (p->max_sectors > (ub->dev_info.max_io_buf_bytes >> 9))
             return -EINVAL;
     } else
         return -EINVAL;
 
     if (ub->params.types & UBLK_PARAM_TYPE_DISCARD) {
         const struct ublk_param_discard *p = &ub->params.discard;
 
         /* So far, only support single segment discard */
         if (p->max_discard_sectors && p->max_discard_segments != 1)
             return -EINVAL;
 
         if (!p->discard_granularity)
             return -EINVAL;
     }
 
     return 0;
 }
 
 static int ublk_apply_params(struct ublk_device *ub)
 {
     if (!(ub->params.types & UBLK_PARAM_TYPE_BASIC))
         return -EINVAL;
 
     ublk_dev_param_basic_apply(ub);
 
     if (ub->params.types & UBLK_PARAM_TYPE_DISCARD)
         ublk_dev_param_discard_apply(ub);
 
     return 0;
 }
 
 static inline bool ublk_can_use_task_work(const struct ublk_queue *ubq)
 {
     if (IS_BUILTIN(CONFIG_BLK_DEV_UBLK) &&
             !(ubq->flags & UBLK_F_URING_CMD_COMP_IN_TASK))
         return true;
     return false;
 }
 
 static inline bool ublk_need_get_data(const struct ublk_queue *ubq)
 {
     if (ubq->flags & UBLK_F_NEED_GET_DATA)
         return true;
     return false;
 }
 
 static struct ublk_device *ublk_get_device(struct ublk_device *ub)
 {
     if (kobject_get_unless_zero(&ub->cdev_dev.kobj))
         return ub;
     return NULL;
 }
 
 static void ublk_put_device(struct ublk_device *ub)
 {
     put_device(&ub->cdev_dev);
 }
 
 static inline struct ublk_queue *ublk_get_queue(struct ublk_device *dev,
         int qid)
 {
        return (struct ublk_queue *)&(dev->__queues[qid * dev->queue_size]);
 }
 
 static inline bool ublk_rq_has_data(const struct request *rq)
 {
     return rq->bio && bio_has_data(rq->bio);
 }
 
 static inline struct ublksrv_io_desc *ublk_get_iod(struct ublk_queue *ubq,
         int tag)
 {
     return (struct ublksrv_io_desc *)
         &(ubq->io_cmd_buf[tag * sizeof(struct ublksrv_io_desc)]);
 }
 
 static inline char *ublk_queue_cmd_buf(struct ublk_device *ub, int q_id)
 {
     return ublk_get_queue(ub, q_id)->io_cmd_buf;
 }
 
 static inline int ublk_queue_cmd_buf_size(struct ublk_device *ub, int q_id)
 {
     struct ublk_queue *ubq = ublk_get_queue(ub, q_id);
 
     return round_up(ubq->q_depth * sizeof(struct ublksrv_io_desc),
             PAGE_SIZE);
 }
 
 static void ublk_free_disk(struct gendisk *disk)
 {
     struct ublk_device *ub = disk->private_data;
 
     clear_bit(UB_STATE_USED, &ub->state);
     put_device(&ub->cdev_dev);
 }
 
 static const struct block_device_operations ub_fops = {
     .owner =    THIS_MODULE,
     .free_disk =    ublk_free_disk,
 };
 
 #define UBLK_MAX_PIN_PAGES  32
 
 struct ublk_map_data {
     const struct ublk_queue *ubq;
     const struct request *rq;
     const struct ublk_io *io;
     unsigned max_bytes;
 };
 
 struct ublk_io_iter {
     struct page *pages[UBLK_MAX_PIN_PAGES];
     unsigned pg_off;    /* offset in the 1st page in pages */
     int nr_pages;       /* how many page pointers in pages */
     struct bio *bio;
     struct bvec_iter iter;
 };
 
 static inline unsigned ublk_copy_io_pages(struct ublk_io_iter *data,
         unsigned max_bytes, bool to_vm)
 {
     const unsigned total = min_t(unsigned, max_bytes,
             PAGE_SIZE - data->pg_off +
             ((data->nr_pages - 1) << PAGE_SHIFT));
     unsigned done = 0;
     unsigned pg_idx = 0;
 
     while (done < total) {
         struct bio_vec bv = bio_iter_iovec(data->bio, data->iter);
         const unsigned int bytes = min3(bv.bv_len, total - done,
                 (unsigned)(PAGE_SIZE - data->pg_off));
         void *bv_buf = bvec_kmap_local(&bv);
         void *pg_buf = kmap_local_page(data->pages[pg_idx]);
 
         if (to_vm)
             memcpy(pg_buf + data->pg_off, bv_buf, bytes);
         else
             memcpy(bv_buf, pg_buf + data->pg_off, bytes);
 
         kunmap_local(pg_buf);
         kunmap_local(bv_buf);
 
         /* advance page array */
         data->pg_off += bytes;
         if (data->pg_off == PAGE_SIZE) {
             pg_idx += 1;
             data->pg_off = 0;
         }
 
         done += bytes;
 
         /* advance bio */
         bio_advance_iter_single(data->bio, &data->iter, bytes);
         if (!data->iter.bi_size) {
             data->bio = data->bio->bi_next;
             if (data->bio == NULL)
                 break;
             data->iter = data->bio->bi_iter;
         }
     }
 
     return done;
 }
 
 static inline int ublk_copy_user_pages(struct ublk_map_data *data,
         bool to_vm)
 {
     const unsigned int gup_flags = to_vm ? FOLL_WRITE : 0;
     const unsigned long start_vm = data->io->addr;
     unsigned int done = 0;
     struct ublk_io_iter iter = {
         .pg_off = start_vm & (PAGE_SIZE - 1),
         .bio    = data->rq->bio,
         .iter   = data->rq->bio->bi_iter,
     };
     const unsigned int nr_pages = round_up(data->max_bytes +
             (start_vm & (PAGE_SIZE - 1)), PAGE_SIZE) >> PAGE_SHIFT;
 
     while (done < nr_pages) {
         const unsigned to_pin = min_t(unsigned, UBLK_MAX_PIN_PAGES,
                 nr_pages - done);
         unsigned i, len;
 
         iter.nr_pages = get_user_pages_fast(start_vm +
                 (done << PAGE_SHIFT), to_pin, gup_flags,
                 iter.pages);
         if (iter.nr_pages <= 0)
             return done == 0 ? iter.nr_pages : done;
         len = ublk_copy_io_pages(&iter, data->max_bytes, to_vm);
         for (i = 0; i < iter.nr_pages; i++) {
             if (to_vm)
                 set_page_dirty(iter.pages[i]);
             put_page(iter.pages[i]);
         }
         data->max_bytes -= len;
         done += iter.nr_pages;
     }
 
     return done;
 }
 
 static int ublk_map_io(const struct ublk_queue *ubq, const struct request *req,
         struct ublk_io *io)
 {
     const unsigned int rq_bytes = blk_rq_bytes(req);
     /*
      * no zero copy, we delay copy WRITE request data into ublksrv
      * context and the big benefit is that pinning pages in current
      * context is pretty fast, see ublk_pin_user_pages
      */
     if (req_op(req) != REQ_OP_WRITE && req_op(req) != REQ_OP_FLUSH)
         return rq_bytes;
 
     if (ublk_rq_has_data(req)) {
         struct ublk_map_data data = {
             .ubq    =   ubq,
             .rq =   req,
             .io =   io,
             .max_bytes =    rq_bytes,
         };
 
         ublk_copy_user_pages(&data, true);
 
         return rq_bytes - data.max_bytes;
     }
     return rq_bytes;
 }
 
 static int ublk_unmap_io(const struct ublk_queue *ubq,
         const struct request *req,
         struct ublk_io *io)
 {
     const unsigned int rq_bytes = blk_rq_bytes(req);
 
     if (req_op(req) == REQ_OP_READ && ublk_rq_has_data(req)) {
         struct ublk_map_data data = {
             .ubq    =   ubq,
             .rq =   req,
             .io =   io,
             .max_bytes =    io->res,
         };
 
         WARN_ON_ONCE(io->res > rq_bytes);
 
         ublk_copy_user_pages(&data, false);
 
         return io->res - data.max_bytes;
     }
     return rq_bytes;
 }
 
 static inline unsigned int ublk_req_build_flags(struct request *req)
 {
     unsigned flags = 0;
 
     if (req->cmd_flags & REQ_FAILFAST_DEV)
         flags |= UBLK_IO_F_FAILFAST_DEV;
 
     if (req->cmd_flags & REQ_FAILFAST_TRANSPORT)
         flags |= UBLK_IO_F_FAILFAST_TRANSPORT;
 
     if (req->cmd_flags & REQ_FAILFAST_DRIVER)
         flags |= UBLK_IO_F_FAILFAST_DRIVER;
 
     if (req->cmd_flags & REQ_META)
         flags |= UBLK_IO_F_META;
 
     if (req->cmd_flags & REQ_FUA)
         flags |= UBLK_IO_F_FUA;
 
     if (req->cmd_flags & REQ_NOUNMAP)
         flags |= UBLK_IO_F_NOUNMAP;
 
     if (req->cmd_flags & REQ_SWAP)
         flags |= UBLK_IO_F_SWAP;
 
     return flags;
 }
 
 static blk_status_t ublk_setup_iod(struct ublk_queue *ubq, struct request *req)
 {
     struct ublksrv_io_desc *iod = ublk_get_iod(ubq, req->tag);
     struct ublk_io *io = &ubq->ios[req->tag];
     u32 ublk_op;
 
     switch (req_op(req)) {
     case REQ_OP_READ:
         ublk_op = UBLK_IO_OP_READ;
         break;
     case REQ_OP_WRITE:
         ublk_op = UBLK_IO_OP_WRITE;
         break;
     case REQ_OP_FLUSH:
         ublk_op = UBLK_IO_OP_FLUSH;
         break;
     case REQ_OP_DISCARD:
         ublk_op = UBLK_IO_OP_DISCARD;
         break;
     case REQ_OP_WRITE_ZEROES:
         ublk_op = UBLK_IO_OP_WRITE_ZEROES;
         break;
     default:
         return BLK_STS_IOERR;
     }
 
     /* need to translate since kernel may change */
     iod->op_flags = ublk_op | ublk_req_build_flags(req);
     iod->nr_sectors = blk_rq_sectors(req);
     iod->start_sector = blk_rq_pos(req);
     iod->addr = io->addr;
 
     return BLK_STS_OK;
 }
 
 static inline struct ublk_uring_cmd_pdu *ublk_get_uring_cmd_pdu(
         struct io_uring_cmd *ioucmd)
 {
     return (struct ublk_uring_cmd_pdu *)&ioucmd->pdu;
 }
 
 static inline bool ubq_daemon_is_dying(struct ublk_queue *ubq)
 {
     return ubq->ubq_daemon->flags & PF_EXITING;
 }
 
 /* todo: handle partial completion */
 static void ublk_complete_rq(struct request *req)
 {
     struct ublk_queue *ubq = req->mq_hctx->driver_data;
     struct ublk_io *io = &ubq->ios[req->tag];
     unsigned int unmapped_bytes;
 
     /* failed read IO if nothing is read */
     if (!io->res && req_op(req) == REQ_OP_READ)
         io->res = -EIO;
 
     if (io->res < 0) {
         blk_mq_end_request(req, errno_to_blk_status(io->res));
         return;
     }
 
     /*
      * FLUSH or DISCARD usually won't return bytes returned, so end them
      * directly.
      *
      * Both the two needn't unmap.
      */
     if (req_op(req) != REQ_OP_READ && req_op(req) != REQ_OP_WRITE) {
         blk_mq_end_request(req, BLK_STS_OK);
         return;
     }
 
     /* for READ request, writing data in iod->addr to rq buffers */
     unmapped_bytes = ublk_unmap_io(ubq, req, io);
 
     /*
      * Extremely impossible since we got data filled in just before
      *
      * Re-read simply for this unlikely case.
      */
     if (unlikely(unmapped_bytes < io->res))
         io->res = unmapped_bytes;
 
     if (blk_update_request(req, BLK_STS_OK, io->res))
         blk_mq_requeue_request(req, true);
     else
         __blk_mq_end_request(req, BLK_STS_OK);
 }
 
 /*
  * Since __ublk_rq_task_work always fails requests immediately during
  * exiting, __ublk_fail_req() is only called from abort context during
  * exiting. So lock is unnecessary.
  *
  * Also aborting may not be started yet, keep in mind that one failed
  * request may be issued by block layer again.
  */
 static void __ublk_fail_req(struct ublk_io *io, struct request *req)
 {
     WARN_ON_ONCE(io->flags & UBLK_IO_FLAG_ACTIVE);
 
     if (!(io->flags & UBLK_IO_FLAG_ABORTED)) {
         io->flags |= UBLK_IO_FLAG_ABORTED;
         blk_mq_end_request(req, BLK_STS_IOERR);
     }
 }
 
 static void ubq_complete_io_cmd(struct ublk_io *io, int res)
 {
     /* mark this cmd owned by ublksrv */
     io->flags |= UBLK_IO_FLAG_OWNED_BY_SRV;
 
     /*
      * clear ACTIVE since we are done with this sqe/cmd slot
      * We can only accept io cmd in case of being not active.
      */
     io->flags &= ~UBLK_IO_FLAG_ACTIVE;
 
     /* tell ublksrv one io request is coming */
     io_uring_cmd_done(io->cmd, res, 0);
 }
 
 #define UBLK_REQUEUE_DELAY_MS   3
 
 static inline void __ublk_rq_task_work(struct request *req)
 {
     struct ublk_queue *ubq = req->mq_hctx->driver_data;
     struct ublk_device *ub = ubq->dev;
     int tag = req->tag;
     struct ublk_io *io = &ubq->ios[tag];
     bool task_exiting = current != ubq->ubq_daemon || ubq_daemon_is_dying(ubq);
     unsigned int mapped_bytes;
 
     pr_devel("%s: complete: op %d, qid %d tag %d io_flags %x addr %llx\n",
             __func__, io->cmd->cmd_op, ubq->q_id, req->tag, io->flags,
             ublk_get_iod(ubq, req->tag)->addr);
 
     if (unlikely(task_exiting)) {
         blk_mq_end_request(req, BLK_STS_IOERR);
         mod_delayed_work(system_wq, &ub->monitor_work, 0);
         return;
     }
 
     if (ublk_need_get_data(ubq) &&
             (req_op(req) == REQ_OP_WRITE ||
             req_op(req) == REQ_OP_FLUSH)) {
         /*
          * We have not handled UBLK_IO_NEED_GET_DATA command yet,
          * so immepdately pass UBLK_IO_RES_NEED_GET_DATA to ublksrv
          * and notify it.
          */
         if (!(io->flags & UBLK_IO_FLAG_NEED_GET_DATA)) {
             io->flags |= UBLK_IO_FLAG_NEED_GET_DATA;
             pr_devel("%s: need get data. op %d, qid %d tag %d io_flags %x\n",
                     __func__, io->cmd->cmd_op, ubq->q_id,
                     req->tag, io->flags);
             ubq_complete_io_cmd(io, UBLK_IO_RES_NEED_GET_DATA);
             return;
         }
         /*
          * We have handled UBLK_IO_NEED_GET_DATA command,
          * so clear UBLK_IO_FLAG_NEED_GET_DATA now and just
          * do the copy work.
          */
         io->flags &= ~UBLK_IO_FLAG_NEED_GET_DATA;
         /* update iod->addr because ublksrv may have passed a new io buffer */
         ublk_get_iod(ubq, req->tag)->addr = io->addr;
         pr_devel("%s: update iod->addr: op %d, qid %d tag %d io_flags %x addr %llx\n",
                 __func__, io->cmd->cmd_op, ubq->q_id, req->tag, io->flags,
                 ublk_get_iod(ubq, req->tag)->addr);
     }
 
     mapped_bytes = ublk_map_io(ubq, req, io);
 
     /* partially mapped, update io descriptor */
     if (unlikely(mapped_bytes != blk_rq_bytes(req))) {
         /*
          * Nothing mapped, retry until we succeed.
          *
          * We may never succeed in mapping any bytes here because
          * of OOM. TODO: reserve one buffer with single page pinned
          * for providing forward progress guarantee.
          */
         if (unlikely(!mapped_bytes)) {
             blk_mq_requeue_request(req, false);
             blk_mq_delay_kick_requeue_list(req->q,
                     UBLK_REQUEUE_DELAY_MS);
             return;
         }
 
         ublk_get_iod(ubq, req->tag)->nr_sectors =
             mapped_bytes >> 9;
     }
 
     ubq_complete_io_cmd(io, UBLK_IO_RES_OK);
 }
 
 static void ublk_rq_task_work_cb(struct io_uring_cmd *cmd)
 {
     struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
 
     __ublk_rq_task_work(pdu->req);
 }
 
 static void ublk_rq_task_work_fn(struct callback_head *work)
 {
     struct ublk_rq_data *data = container_of(work,
             struct ublk_rq_data, work);
     struct request *req = blk_mq_rq_from_pdu(data);
 
     __ublk_rq_task_work(req);
 }
 
 static blk_status_t ublk_queue_rq(struct blk_mq_hw_ctx *hctx,
         const struct blk_mq_queue_data *bd)
 {
     struct ublk_queue *ubq = hctx->driver_data;
     struct request *rq = bd->rq;
     blk_status_t res;
 
     /* fill iod to slot in io cmd buffer */
     res = ublk_setup_iod(ubq, rq);
     if (unlikely(res != BLK_STS_OK))
         return BLK_STS_IOERR;
 
     blk_mq_start_request(bd->rq);
 
     if (unlikely(ubq_daemon_is_dying(ubq))) {
  fail:
         mod_delayed_work(system_wq, &ubq->dev->monitor_work, 0);
         return BLK_STS_IOERR;
     }
 
     if (ublk_can_use_task_work(ubq)) {
         struct ublk_rq_data *data = blk_mq_rq_to_pdu(rq);
         enum task_work_notify_mode notify_mode = bd->last ?
             TWA_SIGNAL_NO_IPI : TWA_NONE;
 
         if (task_work_add(ubq->ubq_daemon, &data->work, notify_mode))
             goto fail;
     } else {
         struct ublk_io *io = &ubq->ios[rq->tag];
         struct io_uring_cmd *cmd = io->cmd;
         struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
 
         /*
          * If the check pass, we know that this is a re-issued request aborted
          * previously in monitor_work because the ubq_daemon(cmd's task) is
          * PF_EXITING. We cannot call io_uring_cmd_complete_in_task() anymore
          * because this ioucmd's io_uring context may be freed now if no inflight
          * ioucmd exists. Otherwise we may cause null-deref in ctx->fallback_work.
          *
          * Note: monitor_work sets UBLK_IO_FLAG_ABORTED and ends this request(releasing
          * the tag). Then the request is re-started(allocating the tag) and we are here.
          * Since releasing/allocating a tag implies smp_mb(), finding UBLK_IO_FLAG_ABORTED
          * guarantees that here is a re-issued request aborted previously.
          */
         if ((io->flags & UBLK_IO_FLAG_ABORTED))
             goto fail;
 
         pdu->req = rq;
         io_uring_cmd_complete_in_task(cmd, ublk_rq_task_work_cb);
     }
 
     return BLK_STS_OK;
 }
 
 static void ublk_commit_rqs(struct blk_mq_hw_ctx *hctx)
 {
     struct ublk_queue *ubq = hctx->driver_data;
 
     if (ublk_can_use_task_work(ubq))
         __set_notify_signal(ubq->ubq_daemon);
 }
 
 static int ublk_init_hctx(struct blk_mq_hw_ctx *hctx, void *driver_data,
         unsigned int hctx_idx)
 {
     struct ublk_device *ub = driver_data;
     struct ublk_queue *ubq = ublk_get_queue(ub, hctx->queue_num);
 
     hctx->driver_data = ubq;
     return 0;
 }
 
 static int ublk_init_rq(struct blk_mq_tag_set *set, struct request *req,
         unsigned int hctx_idx, unsigned int numa_node)
 {
     struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
 
     init_task_work(&data->work, ublk_rq_task_work_fn);
     return 0;
 }
 
 static const struct blk_mq_ops ublk_mq_ops = {
     .queue_rq       = ublk_queue_rq,
     .commit_rqs     = ublk_commit_rqs,
     .init_hctx  = ublk_init_hctx,
     .init_request   = ublk_init_rq,
 };
 
 static int ublk_ch_open(struct inode *inode, struct file *filp)
 {
     struct ublk_device *ub = container_of(inode->i_cdev,
             struct ublk_device, cdev);
 
     if (test_and_set_bit(UB_STATE_OPEN, &ub->state))
         return -EBUSY;
     filp->private_data = ub;
     return 0;
 }
 
 static int ublk_ch_release(struct inode *inode, struct file *filp)
 {
     struct ublk_device *ub = filp->private_data;
 
     clear_bit(UB_STATE_OPEN, &ub->state);
     return 0;
 }
 
 /* map pre-allocated per-queue cmd buffer to ublksrv daemon */
 static int ublk_ch_mmap(struct file *filp, struct vm_area_struct *vma)
 {
     struct ublk_device *ub = filp->private_data;
     size_t sz = vma->vm_end - vma->vm_start;
     unsigned max_sz = UBLK_MAX_QUEUE_DEPTH * sizeof(struct ublksrv_io_desc);
     unsigned long pfn, end, phys_off = vma->vm_pgoff << PAGE_SHIFT;
     int q_id, ret = 0;
 
     spin_lock(&ub->mm_lock);
     if (!ub->mm)
         ub->mm = current->mm;
     if (current->mm != ub->mm)
         ret = -EINVAL;
     spin_unlock(&ub->mm_lock);
 
     if (ret)
         return ret;
 
     if (vma->vm_flags & VM_WRITE)
         return -EPERM;
 
     end = UBLKSRV_CMD_BUF_OFFSET + ub->dev_info.nr_hw_queues * max_sz;
     if (phys_off < UBLKSRV_CMD_BUF_OFFSET || phys_off >= end)
         return -EINVAL;
 
     q_id = (phys_off - UBLKSRV_CMD_BUF_OFFSET) / max_sz;
     pr_devel("%s: qid %d, pid %d, addr %lx pg_off %lx sz %lu\n",
             __func__, q_id, current->pid, vma->vm_start,
             phys_off, (unsigned long)sz);
 
     if (sz != ublk_queue_cmd_buf_size(ub, q_id))
         return -EINVAL;
 
     pfn = virt_to_phys(ublk_queue_cmd_buf(ub, q_id)) >> PAGE_SHIFT;
     return remap_pfn_range(vma, vma->vm_start, pfn, sz, vma->vm_page_prot);
 }
 
 static void ublk_commit_completion(struct ublk_device *ub,
         struct ublksrv_io_cmd *ub_cmd)
 {
     u32 qid = ub_cmd->q_id, tag = ub_cmd->tag;
     struct ublk_queue *ubq = ublk_get_queue(ub, qid);
     struct ublk_io *io = &ubq->ios[tag];
     struct request *req;
 
     /* now this cmd slot is owned by nbd driver */
     io->flags &= ~UBLK_IO_FLAG_OWNED_BY_SRV;
     io->res = ub_cmd->result;
 
     /* find the io request and complete */
     req = blk_mq_tag_to_rq(ub->tag_set.tags[qid], tag);
 
     if (req && likely(!blk_should_fake_timeout(req->q)))
         ublk_complete_rq(req);
 }
 
 /*
  * When ->ubq_daemon is exiting, either new request is ended immediately,
  * or any queued io command is drained, so it is safe to abort queue
  * lockless
  */
 static void ublk_abort_queue(struct ublk_device *ub, struct ublk_queue *ubq)
 {
     int i;
 
     if (!ublk_get_device(ub))
         return;
 
     for (i = 0; i < ubq->q_depth; i++) {
         struct ublk_io *io = &ubq->ios[i];
 
         if (!(io->flags & UBLK_IO_FLAG_ACTIVE)) {
             struct request *rq;
 
             /*
              * Either we fail the request or ublk_rq_task_work_fn
              * will do it
              */
             rq = blk_mq_tag_to_rq(ub->tag_set.tags[ubq->q_id], i);
             if (rq)
                 __ublk_fail_req(io, rq);
         }
     }
     ublk_put_device(ub);
 }
 
 static void ublk_daemon_monitor_work(struct work_struct *work)
 {
     struct ublk_device *ub =
         container_of(work, struct ublk_device, monitor_work.work);
     int i;
 
     for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {
         struct ublk_queue *ubq = ublk_get_queue(ub, i);
 
         if (ubq_daemon_is_dying(ubq)) {
             schedule_work(&ub->stop_work);
 
             /* abort queue is for making forward progress */
             ublk_abort_queue(ub, ubq);
         }
     }
 
     /*
      * We can't schedule monitor work after ublk_remove() is started.
      *
      * No need ub->mutex, monitor work are canceled after state is marked
      * as DEAD, so DEAD state is observed reliably.
      */
     if (ub->dev_info.state != UBLK_S_DEV_DEAD)
         schedule_delayed_work(&ub->monitor_work,
                 UBLK_DAEMON_MONITOR_PERIOD);
 }
 
 static inline bool ublk_queue_ready(struct ublk_queue *ubq)
 {
     return ubq->nr_io_ready == ubq->q_depth;
 }
 
 static void ublk_cancel_queue(struct ublk_queue *ubq)
 {
     int i;
 
     if (!ublk_queue_ready(ubq))
         return;
 
     for (i = 0; i < ubq->q_depth; i++) {
         struct ublk_io *io = &ubq->ios[i];
 
         if (io->flags & UBLK_IO_FLAG_ACTIVE)
             io_uring_cmd_done(io->cmd, UBLK_IO_RES_ABORT, 0);
     }
 
     /* all io commands are canceled */
     ubq->nr_io_ready = 0;
 }
 
 /* Cancel all pending commands, must be called after del_gendisk() returns */
 static void ublk_cancel_dev(struct ublk_device *ub)
 {
     int i;
 
     for (i = 0; i < ub->dev_info.nr_hw_queues; i++)
         ublk_cancel_queue(ublk_get_queue(ub, i));
 }
 
 static void ublk_stop_dev(struct ublk_device *ub)
 {
     mutex_lock(&ub->mutex);
     if (ub->dev_info.state != UBLK_S_DEV_LIVE)
         goto unlock;
 
     del_gendisk(ub->ub_disk);
     ub->dev_info.state = UBLK_S_DEV_DEAD;
     ub->dev_info.ublksrv_pid = -1;
     put_disk(ub->ub_disk);
     ub->ub_disk = NULL;
  unlock:
     ublk_cancel_dev(ub);
     mutex_unlock(&ub->mutex);
     cancel_delayed_work_sync(&ub->monitor_work);
 }
 
 /* device can only be started after all IOs are ready */
 static void ublk_mark_io_ready(struct ublk_device *ub, struct ublk_queue *ubq)
 {
     mutex_lock(&ub->mutex);
     ubq->nr_io_ready++;
     if (ublk_queue_ready(ubq)) {
         ubq->ubq_daemon = current;
         get_task_struct(ubq->ubq_daemon);
         ub->nr_queues_ready++;
     }
     if (ub->nr_queues_ready == ub->dev_info.nr_hw_queues)
         complete_all(&ub->completion);
     mutex_unlock(&ub->mutex);
 }
 
 static void ublk_handle_need_get_data(struct ublk_device *ub, int q_id,
         int tag, struct io_uring_cmd *cmd)
 {
     struct ublk_queue *ubq = ublk_get_queue(ub, q_id);
     struct request *req = blk_mq_tag_to_rq(ub->tag_set.tags[q_id], tag);
 
     if (ublk_can_use_task_work(ubq)) {
         struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
 
         /* should not fail since we call it just in ubq->ubq_daemon */
         task_work_add(ubq->ubq_daemon, &data->work, TWA_SIGNAL_NO_IPI);
     } else {
         struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
 
         pdu->req = req;
         io_uring_cmd_complete_in_task(cmd, ublk_rq_task_work_cb);
     }
 }
 
 static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
 {
     struct ublksrv_io_cmd *ub_cmd = (struct ublksrv_io_cmd *)cmd->cmd;
     struct ublk_device *ub = cmd->file->private_data;
     struct ublk_queue *ubq;
     struct ublk_io *io;
     u32 cmd_op = cmd->cmd_op;
     unsigned tag = ub_cmd->tag;
     int ret = -EINVAL;
 
     pr_devel("%s: received: cmd op %d queue %d tag %d result %d\n",
             __func__, cmd->cmd_op, ub_cmd->q_id, tag,
             ub_cmd->result);
 
     if (!(issue_flags & IO_URING_F_SQE128))
         goto out;
 
     if (ub_cmd->q_id >= ub->dev_info.nr_hw_queues)
         goto out;
 
     ubq = ublk_get_queue(ub, ub_cmd->q_id);
     if (!ubq || ub_cmd->q_id != ubq->q_id)
         goto out;
 
     if (ubq->ubq_daemon && ubq->ubq_daemon != current)
         goto out;
 
     if (tag >= ubq->q_depth)
         goto out;
 
     io = &ubq->ios[tag];
 
     /* there is pending io cmd, something must be wrong */
     if (io->flags & UBLK_IO_FLAG_ACTIVE) {
         ret = -EBUSY;
         goto out;
     }
 
     /*
      * ensure that the user issues UBLK_IO_NEED_GET_DATA
      * iff the driver have set the UBLK_IO_FLAG_NEED_GET_DATA.
      */
     if ((!!(io->flags & UBLK_IO_FLAG_NEED_GET_DATA))
             ^ (cmd_op == UBLK_IO_NEED_GET_DATA))
         goto out;
 
     switch (cmd_op) {
     case UBLK_IO_FETCH_REQ:
         /* UBLK_IO_FETCH_REQ is only allowed before queue is setup */
         if (ublk_queue_ready(ubq)) {
             ret = -EBUSY;
             goto out;
         }
         /*
          * The io is being handled by server, so COMMIT_RQ is expected
          * instead of FETCH_REQ
          */
         if (io->flags & UBLK_IO_FLAG_OWNED_BY_SRV)
             goto out;
         /* FETCH_RQ has to provide IO buffer */
         if (!ub_cmd->addr)
             goto out;
         io->cmd = cmd;
         io->flags |= UBLK_IO_FLAG_ACTIVE;
         io->addr = ub_cmd->addr;
 
         ublk_mark_io_ready(ub, ubq);
         break;
     case UBLK_IO_COMMIT_AND_FETCH_REQ:
         /* FETCH_RQ has to provide IO buffer */
         if (!ub_cmd->addr)
             goto out;
         if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV))
             goto out;
         io->addr = ub_cmd->addr;
         io->flags |= UBLK_IO_FLAG_ACTIVE;
         io->cmd = cmd;
         ublk_commit_completion(ub, ub_cmd);
         break;
     case UBLK_IO_NEED_GET_DATA:
         if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV))
             goto out;
         io->addr = ub_cmd->addr;
         io->cmd = cmd;
         io->flags |= UBLK_IO_FLAG_ACTIVE;
         ublk_handle_need_get_data(ub, ub_cmd->q_id, ub_cmd->tag, cmd);
         break;
     default:
         goto out;
     }
     return -EIOCBQUEUED;
 
  out:
     io_uring_cmd_done(cmd, ret, 0);
     pr_devel("%s: complete: cmd op %d, tag %d ret %x io_flags %x\n",
             __func__, cmd_op, tag, ret, io->flags);
     return -EIOCBQUEUED;
 }
 
 static const struct file_operations ublk_ch_fops = {
     .owner = THIS_MODULE,
     .open = ublk_ch_open,
     .release = ublk_ch_release,
     .llseek = no_llseek,
     .uring_cmd = ublk_ch_uring_cmd,
     .mmap = ublk_ch_mmap,
 };
 
 static void ublk_deinit_queue(struct ublk_device *ub, int q_id)
 {
     int size = ublk_queue_cmd_buf_size(ub, q_id);
     struct ublk_queue *ubq = ublk_get_queue(ub, q_id);
 
     if (ubq->ubq_daemon)
         put_task_struct(ubq->ubq_daemon);
     if (ubq->io_cmd_buf)
         free_pages((unsigned long)ubq->io_cmd_buf, get_order(size));
 }
 
 static int ublk_init_queue(struct ublk_device *ub, int q_id)
 {
     struct ublk_queue *ubq = ublk_get_queue(ub, q_id);
     gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO;
     void *ptr;
     int size;
 
     ubq->flags = ub->dev_info.flags;
     ubq->q_id = q_id;
     ubq->q_depth = ub->dev_info.queue_depth;
     size = ublk_queue_cmd_buf_size(ub, q_id);
 
     ptr = (void *) __get_free_pages(gfp_flags, get_order(size));
     if (!ptr)
         return -ENOMEM;
 
     ubq->io_cmd_buf = ptr;
     ubq->dev = ub;
     return 0;
 }
 
 static void ublk_deinit_queues(struct ublk_device *ub)
 {
     int nr_queues = ub->dev_info.nr_hw_queues;
     int i;
 
     if (!ub->__queues)
         return;
 
     for (i = 0; i < nr_queues; i++)
         ublk_deinit_queue(ub, i);
     kfree(ub->__queues);
 }
 
 static int ublk_init_queues(struct ublk_device *ub)
 {
     int nr_queues = ub->dev_info.nr_hw_queues;
     int depth = ub->dev_info.queue_depth;
     int ubq_size = sizeof(struct ublk_queue) + depth * sizeof(struct ublk_io);
     int i, ret = -ENOMEM;
 
     ub->queue_size = ubq_size;
     ub->__queues = kcalloc(nr_queues, ubq_size, GFP_KERNEL);
     if (!ub->__queues)
         return ret;
 
     for (i = 0; i < nr_queues; i++) {
         if (ublk_init_queue(ub, i))
             goto fail;
     }
 
     init_completion(&ub->completion);
     return 0;
 
  fail:
     ublk_deinit_queues(ub);
     return ret;
 }
 
 static int ublk_alloc_dev_number(struct ublk_device *ub, int idx)
 {
     int i = idx;
     int err;
 
     spin_lock(&ublk_idr_lock);
     /* allocate id, if @id >= 0, we're requesting that specific id */
     if (i >= 0) {
         err = idr_alloc(&ublk_index_idr, ub, i, i + 1, GFP_NOWAIT);
         if (err == -ENOSPC)
             err = -EEXIST;
     } else {
         err = idr_alloc(&ublk_index_idr, ub, 0, 0, GFP_NOWAIT);
     }
     spin_unlock(&ublk_idr_lock);
 
     if (err >= 0)
         ub->ub_number = err;
 
     return err;
 }
 
 static void ublk_free_dev_number(struct ublk_device *ub)
 {
     spin_lock(&ublk_idr_lock);
     idr_remove(&ublk_index_idr, ub->ub_number);
     wake_up_all(&ublk_idr_wq);
     spin_unlock(&ublk_idr_lock);
 }
 
 static void ublk_cdev_rel(struct device *dev)
 {
     struct ublk_device *ub = container_of(dev, struct ublk_device, cdev_dev);
 
     blk_mq_free_tag_set(&ub->tag_set);
     ublk_deinit_queues(ub);
     ublk_free_dev_number(ub);
     mutex_destroy(&ub->mutex);
     kfree(ub);
 }
 
 static int ublk_add_chdev(struct ublk_device *ub)
 {
     struct device *dev = &ub->cdev_dev;
     int minor = ub->ub_number;
     int ret;
 
     dev->parent = ublk_misc.this_device;
     dev->devt = MKDEV(MAJOR(ublk_chr_devt), minor);
     dev->class = ublk_chr_class;
     dev->release = ublk_cdev_rel;
     device_initialize(dev);
 
     ret = dev_set_name(dev, "ublkc%d", minor);
     if (ret)
         goto fail;
 
     cdev_init(&ub->cdev, &ublk_ch_fops);
     ret = cdev_device_add(&ub->cdev, dev);
     if (ret)
         goto fail;
     return 0;
  fail:
     put_device(dev);
     return ret;
 }
 
 static void ublk_stop_work_fn(struct work_struct *work)
 {
     struct ublk_device *ub =
         container_of(work, struct ublk_device, stop_work);
 
     ublk_stop_dev(ub);
 }
 
 /* align max io buffer size with PAGE_SIZE */
 static void ublk_align_max_io_size(struct ublk_device *ub)
 {
     unsigned int max_io_bytes = ub->dev_info.max_io_buf_bytes;
 
     ub->dev_info.max_io_buf_bytes =
         round_down(max_io_bytes, PAGE_SIZE);
 }
 
 static int ublk_add_tag_set(struct ublk_device *ub)
 {
     ub->tag_set.ops = &ublk_mq_ops;
     ub->tag_set.nr_hw_queues = ub->dev_info.nr_hw_queues;
     ub->tag_set.queue_depth = ub->dev_info.queue_depth;
     ub->tag_set.numa_node = NUMA_NO_NODE;
     ub->tag_set.cmd_size = sizeof(struct ublk_rq_data);
     ub->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
     ub->tag_set.driver_data = ub;
     return blk_mq_alloc_tag_set(&ub->tag_set);
 }
 
 static void ublk_remove(struct ublk_device *ub)
 {
     ublk_stop_dev(ub);
     cancel_work_sync(&ub->stop_work);
     cdev_device_del(&ub->cdev, &ub->cdev_dev);
     put_device(&ub->cdev_dev);
 }
 
 static struct ublk_device *ublk_get_device_from_id(int idx)
 {
     struct ublk_device *ub = NULL;
 
     if (idx < 0)
         return NULL;
 
     spin_lock(&ublk_idr_lock);
     ub = idr_find(&ublk_index_idr, idx);
     if (ub)
         ub = ublk_get_device(ub);
     spin_unlock(&ublk_idr_lock);
 
     return ub;
 }
 
 static int ublk_ctrl_start_dev(struct io_uring_cmd *cmd)
 {
     struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
     int ublksrv_pid = (int)header->data[0];
     struct ublk_device *ub;
     struct gendisk *disk;
     int ret = -EINVAL;
 
     if (ublksrv_pid <= 0)
         return -EINVAL;
 
     ub = ublk_get_device_from_id(header->dev_id);
     if (!ub)
         return -EINVAL;
 
     wait_for_completion_interruptible(&ub->completion);
 
     schedule_delayed_work(&ub->monitor_work, UBLK_DAEMON_MONITOR_PERIOD);
 
     mutex_lock(&ub->mutex);
     if (ub->dev_info.state == UBLK_S_DEV_LIVE ||
         test_bit(UB_STATE_USED, &ub->state)) {
         ret = -EEXIST;
         goto out_unlock;
     }
 
     disk = blk_mq_alloc_disk(&ub->tag_set, ub);
     if (IS_ERR(disk)) {
         ret = PTR_ERR(disk);
         goto out_unlock;
     }
     sprintf(disk->disk_name, "ublkb%d", ub->ub_number);
     disk->fops = &ub_fops;
     disk->private_data = ub;
 
     ub->dev_info.ublksrv_pid = ublksrv_pid;
     ub->ub_disk = disk;
 
     ret = ublk_apply_params(ub);
     if (ret)
         goto out_put_disk;
 
     get_device(&ub->cdev_dev);
     ret = add_disk(disk);
     if (ret) {
         /*
          * Has to drop the reference since ->free_disk won't be
          * called in case of add_disk failure.
          */
         ublk_put_device(ub);
         goto out_put_disk;
     }
     set_bit(UB_STATE_USED, &ub->state);
     ub->dev_info.state = UBLK_S_DEV_LIVE;
 out_put_disk:
     if (ret)
         put_disk(disk);
 out_unlock:
     mutex_unlock(&ub->mutex);
     ublk_put_device(ub);
     return ret;
 }
 
 static int ublk_ctrl_get_queue_affinity(struct io_uring_cmd *cmd)
 {
     struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
     void __user *argp = (void __user *)(unsigned long)header->addr;
     struct ublk_device *ub;
     cpumask_var_t cpumask;
     unsigned long queue;
     unsigned int retlen;
     unsigned int i;
     int ret = -EINVAL;
     
     if (header->len * BITS_PER_BYTE < nr_cpu_ids)
         return -EINVAL;
     if (header->len & (sizeof(unsigned long)-1))
         return -EINVAL;
     if (!header->addr)
         return -EINVAL;
 
     ub = ublk_get_device_from_id(header->dev_id);
     if (!ub)
         return -EINVAL;
 
     queue = header->data[0];
     if (queue >= ub->dev_info.nr_hw_queues)
         goto out_put_device;
 
     ret = -ENOMEM;
     if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
         goto out_put_device;
 
     for_each_possible_cpu(i) {
         if (ub->tag_set.map[HCTX_TYPE_DEFAULT].mq_map[i] == queue)
             cpumask_set_cpu(i, cpumask);
     }
 
     ret = -EFAULT;
     retlen = min_t(unsigned short, header->len, cpumask_size());
     if (copy_to_user(argp, cpumask, retlen))
         goto out_free_cpumask;
     if (retlen != header->len &&
         clear_user(argp + retlen, header->len - retlen))
         goto out_free_cpumask;
 
     ret = 0;
 out_free_cpumask:
     free_cpumask_var(cpumask);
 out_put_device:
     ublk_put_device(ub);
     return ret;
 }
 
 static inline void ublk_dump_dev_info(struct ublksrv_ctrl_dev_info *info)
 {
     pr_devel("%s: dev id %d flags %llx\n", __func__,
             info->dev_id, info->flags);
     pr_devel("\t nr_hw_queues %d queue_depth %d\n",
             info->nr_hw_queues, info->queue_depth);
 }
 
 static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
 {
     struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
     void __user *argp = (void __user *)(unsigned long)header->addr;
     struct ublksrv_ctrl_dev_info info;
     struct ublk_device *ub;
     int ret = -EINVAL;
 
     if (header->len < sizeof(info) || !header->addr)
         return -EINVAL;
     if (header->queue_id != (u16)-1) {
         pr_warn("%s: queue_id is wrong %x\n",
             __func__, header->queue_id);
         return -EINVAL;
     }
     if (copy_from_user(&info, argp, sizeof(info)))
         return -EFAULT;
     ublk_dump_dev_info(&info);
     if (header->dev_id != info.dev_id) {
         pr_warn("%s: dev id not match %u %u\n",
             __func__, header->dev_id, info.dev_id);
         return -EINVAL;
     }
 
     ret = mutex_lock_killable(&ublk_ctl_mutex);
     if (ret)
         return ret;
 
     ret = -ENOMEM;
     ub = kzalloc(sizeof(*ub), GFP_KERNEL);
     if (!ub)
         goto out_unlock;
     mutex_init(&ub->mutex);
     spin_lock_init(&ub->mm_lock);
     INIT_WORK(&ub->stop_work, ublk_stop_work_fn);
     INIT_DELAYED_WORK(&ub->monitor_work, ublk_daemon_monitor_work);
 
     ret = ublk_alloc_dev_number(ub, header->dev_id);
     if (ret < 0)
         goto out_free_ub;
 
     memcpy(&ub->dev_info, &info, sizeof(info));
 
     /* update device id */
     ub->dev_info.dev_id = ub->ub_number;
 
     /*
      * 64bit flags will be copied back to userspace as feature
      * negotiation result, so have to clear flags which driver
      * doesn't support yet, then userspace can get correct flags
      * (features) to handle.
      */
     ub->dev_info.flags &= UBLK_F_ALL;
 
     /* We are not ready to support zero copy */
     ub->dev_info.flags &= ~UBLK_F_SUPPORT_ZERO_COPY;
 
     ub->dev_info.nr_hw_queues = min_t(unsigned int,
             ub->dev_info.nr_hw_queues, nr_cpu_ids);
     ublk_align_max_io_size(ub);
 
     ret = ublk_init_queues(ub);
     if (ret)
         goto out_free_dev_number;
 
     ret = ublk_add_tag_set(ub);
     if (ret)
         goto out_deinit_queues;
 
     ret = -EFAULT;
     if (copy_to_user(argp, &ub->dev_info, sizeof(info)))
         goto out_free_tag_set;
 
     /*
      * Add the char dev so that ublksrv daemon can be setup.
      * ublk_add_chdev() will cleanup everything if it fails.
      */
     ret = ublk_add_chdev(ub);
     goto out_unlock;
 
 out_free_tag_set:
     blk_mq_free_tag_set(&ub->tag_set);
 out_deinit_queues:
     ublk_deinit_queues(ub);
 out_free_dev_number:
     ublk_free_dev_number(ub);
 out_free_ub:
     mutex_destroy(&ub->mutex);
     kfree(ub);
 out_unlock:
     mutex_unlock(&ublk_ctl_mutex);
     return ret;
 }
 
 static inline bool ublk_idr_freed(int id)
 {
     void *ptr;
 
     spin_lock(&ublk_idr_lock);
     ptr = idr_find(&ublk_index_idr, id);
     spin_unlock(&ublk_idr_lock);
 
     return ptr == NULL;
 }
 
 static int ublk_ctrl_del_dev(int idx)
 {
     struct ublk_device *ub;
     int ret;
 
     ret = mutex_lock_killable(&ublk_ctl_mutex);
     if (ret)
         return ret;
 
     ub = ublk_get_device_from_id(idx);
     if (ub) {
         ublk_remove(ub);
         ublk_put_device(ub);
         ret = 0;
     } else {
         ret = -ENODEV;
     }
 
     /*
      * Wait until the idr is removed, then it can be reused after
      * DEL_DEV command is returned.
      */
     if (!ret)
         wait_event(ublk_idr_wq, ublk_idr_freed(idx));
     mutex_unlock(&ublk_ctl_mutex);
 
     return ret;
 }
 
 static inline void ublk_ctrl_cmd_dump(struct io_uring_cmd *cmd)
 {
     struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
 
     pr_devel("%s: cmd_op %x, dev id %d qid %d data %llx buf %llx len %u\n",
             __func__, cmd->cmd_op, header->dev_id, header->queue_id,
             header->data[0], header->addr, header->len);
 }
 
 static int ublk_ctrl_stop_dev(struct io_uring_cmd *cmd)
 {
     struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
     struct ublk_device *ub;
 
     ub = ublk_get_device_from_id(header->dev_id);
     if (!ub)
         return -EINVAL;
 
     ublk_stop_dev(ub);
     cancel_work_sync(&ub->stop_work);
 
     ublk_put_device(ub);
     return 0;
 }
 
 static int ublk_ctrl_get_dev_info(struct io_uring_cmd *cmd)
 {
     struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
     void __user *argp = (void __user *)(unsigned long)header->addr;
     struct ublk_device *ub;
     int ret = 0;
 
     if (header->len < sizeof(struct ublksrv_ctrl_dev_info) || !header->addr)
         return -EINVAL;
 
     ub = ublk_get_device_from_id(header->dev_id);
     if (!ub)
         return -EINVAL;
 
     if (copy_to_user(argp, &ub->dev_info, sizeof(ub->dev_info)))
         ret = -EFAULT;
     ublk_put_device(ub);
 
     return ret;
 }
 
 static int ublk_ctrl_get_params(struct io_uring_cmd *cmd)
 {
     struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
     void __user *argp = (void __user *)(unsigned long)header->addr;
     struct ublk_params_header ph;
     struct ublk_device *ub;
     int ret;
 
     if (header->len <= sizeof(ph) || !header->addr)
         return -EINVAL;
 
     if (copy_from_user(&ph, argp, sizeof(ph)))
         return -EFAULT;
 
     if (ph.len > header->len || !ph.len)
         return -EINVAL;
 
     if (ph.len > sizeof(struct ublk_params))
         ph.len = sizeof(struct ublk_params);
 
     ub = ublk_get_device_from_id(header->dev_id);
     if (!ub)
         return -EINVAL;
 
     mutex_lock(&ub->mutex);
     if (copy_to_user(argp, &ub->params, ph.len))
         ret = -EFAULT;
     else
         ret = 0;
     mutex_unlock(&ub->mutex);
 
     ublk_put_device(ub);
     return ret;
 }
 
 static int ublk_ctrl_set_params(struct io_uring_cmd *cmd)
 {
     struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
     void __user *argp = (void __user *)(unsigned long)header->addr;
     struct ublk_params_header ph;
     struct ublk_device *ub;
     int ret = -EFAULT;
 
     if (header->len <= sizeof(ph) || !header->addr)
         return -EINVAL;
 
     if (copy_from_user(&ph, argp, sizeof(ph)))
         return -EFAULT;
 
     if (ph.len > header->len || !ph.len || !ph.types)
         return -EINVAL;
 
     if (ph.len > sizeof(struct ublk_params))
         ph.len = sizeof(struct ublk_params);
 
     ub = ublk_get_device_from_id(header->dev_id);
     if (!ub)
         return -EINVAL;
 
     /* parameters can only be changed when device isn't live */
     mutex_lock(&ub->mutex);
     if (ub->dev_info.state == UBLK_S_DEV_LIVE) {
         ret = -EACCES;
     } else if (copy_from_user(&ub->params, argp, ph.len)) {
         ret = -EFAULT;
     } else {
         /* clear all we don't support yet */
         ub->params.types &= UBLK_PARAM_TYPE_ALL;
         ret = ublk_validate_params(ub);
     }
     mutex_unlock(&ub->mutex);
     ublk_put_device(ub);
 
     return ret;
 }
 
 static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
         unsigned int issue_flags)
 {
     struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
     int ret = -EINVAL;
 
     ublk_ctrl_cmd_dump(cmd);
 
     if (!(issue_flags & IO_URING_F_SQE128))
         goto out;
 
     ret = -EPERM;
     if (!capable(CAP_SYS_ADMIN))
         goto out;
 
     ret = -ENODEV;
     switch (cmd->cmd_op) {
     case UBLK_CMD_START_DEV:
         ret = ublk_ctrl_start_dev(cmd);
         break;
     case UBLK_CMD_STOP_DEV:
         ret = ublk_ctrl_stop_dev(cmd);
         break;
     case UBLK_CMD_GET_DEV_INFO:
         ret = ublk_ctrl_get_dev_info(cmd);
         break;
     case UBLK_CMD_ADD_DEV:
         ret = ublk_ctrl_add_dev(cmd);
         break;
     case UBLK_CMD_DEL_DEV:
         ret = ublk_ctrl_del_dev(header->dev_id);
         break;
     case UBLK_CMD_GET_QUEUE_AFFINITY:
         ret = ublk_ctrl_get_queue_affinity(cmd);
         break;
     case UBLK_CMD_GET_PARAMS:
         ret = ublk_ctrl_get_params(cmd);
         break;
     case UBLK_CMD_SET_PARAMS:
         ret = ublk_ctrl_set_params(cmd);
         break;
     default:
         break;
     }
  out:
     io_uring_cmd_done(cmd, ret, 0);
     pr_devel("%s: cmd done ret %d cmd_op %x, dev id %d qid %d\n",
             __func__, ret, cmd->cmd_op, header->dev_id, header->queue_id);
     return -EIOCBQUEUED;
 }
 
 static const struct file_operations ublk_ctl_fops = {
     .open       = nonseekable_open,
     .uring_cmd      = ublk_ctrl_uring_cmd,
     .owner      = THIS_MODULE,
     .llseek     = noop_llseek,
 };
 
 static struct miscdevice ublk_misc = {
     .minor      = MISC_DYNAMIC_MINOR,
     .name       = "ublk-control",
     .fops       = &ublk_ctl_fops,
 };
 
 static int __init ublk_init(void)
 {
     int ret;
 
     init_waitqueue_head(&ublk_idr_wq);
 
     ret = misc_register(&ublk_misc);
     if (ret)
         return ret;
 
     ret = alloc_chrdev_region(&ublk_chr_devt, 0, UBLK_MINORS, "ublk-char");
     if (ret)
         goto unregister_mis;
 
     ublk_chr_class = class_create(THIS_MODULE, "ublk-char");
     if (IS_ERR(ublk_chr_class)) {
         ret = PTR_ERR(ublk_chr_class);
         goto free_chrdev_region;
     }
     return 0;
 
 free_chrdev_region:
     unregister_chrdev_region(ublk_chr_devt, UBLK_MINORS);
 unregister_mis:
     misc_deregister(&ublk_misc);
     return ret;
 }
 
 static void __exit ublk_exit(void)
 {
     struct ublk_device *ub;
     int id;
 
     class_destroy(ublk_chr_class);
 
     misc_deregister(&ublk_misc);
 
     idr_for_each_entry(&ublk_index_idr, ub, id)
         ublk_remove(ub);
 
     idr_destroy(&ublk_index_idr);
     unregister_chrdev_region(ublk_chr_devt, UBLK_MINORS);
 }
 
 module_init(ublk_init);
 module_exit(ublk_exit);
 
 MODULE_AUTHOR("Ming Lei <ming.lei@redhat.com>");
 MODULE_LICENSE("GPL");

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