diff options
| -rw-r--r-- | drivers/block/loop.c | 233 |
1 files changed, 194 insertions, 39 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 13ce229d450c..9b842d767381 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -68,6 +68,7 @@ struct loop_device { struct rb_root worker_tree; struct timer_list timer; bool sysfs_inited; + unsigned lo_nr_blocking_writes; struct request_queue *lo_queue; struct blk_mq_tag_set tag_set; @@ -90,6 +91,8 @@ struct loop_cmd { #define LOOP_IDLE_WORKER_TIMEOUT (60 * HZ) #define LOOP_DEFAULT_HW_Q_DEPTH 128 +static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd); + static DEFINE_IDR(loop_index_idr); static DEFINE_MUTEX(loop_ctl_mutex); static DEFINE_MUTEX(loop_validate_mutex); @@ -321,6 +324,15 @@ static void lo_rw_aio_do_completion(struct loop_cmd *cmd) if (!atomic_dec_and_test(&cmd->ref)) return; + + /* -EAGAIN could be returned from bdev's ->ki_complete */ + if (cmd->ret == -EAGAIN) { + struct loop_device *lo = rq->q->queuedata; + + loop_queue_work(lo, cmd); + return; + } + kfree(cmd->bvec); cmd->bvec = NULL; if (req_op(rq) == REQ_OP_WRITE) @@ -337,24 +349,28 @@ static void lo_rw_aio_complete(struct kiocb *iocb, long ret) lo_rw_aio_do_completion(cmd); } -static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, - loff_t pos, int rw) +static inline unsigned lo_cmd_nr_bvec(struct loop_cmd *cmd) { - struct iov_iter iter; - struct req_iterator rq_iter; - struct bio_vec *bvec; struct request *rq = blk_mq_rq_from_pdu(cmd); - struct bio *bio = rq->bio; - struct file *file = lo->lo_backing_file; + struct req_iterator rq_iter; struct bio_vec tmp; - unsigned int offset; int nr_bvec = 0; - int ret; rq_for_each_bvec(tmp, rq, rq_iter) nr_bvec++; + return nr_bvec; +} + +static int lo_rw_aio_prep(struct loop_device *lo, struct loop_cmd *cmd, + unsigned nr_bvec, loff_t pos) +{ + struct request *rq = blk_mq_rq_from_pdu(cmd); + if (rq->bio != rq->biotail) { + struct req_iterator rq_iter; + struct bio_vec *bvec; + struct bio_vec tmp; bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec), GFP_NOIO); @@ -372,24 +388,12 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, *bvec = tmp; bvec++; } - bvec = cmd->bvec; - offset = 0; } else { - /* - * Same here, this bio may be started from the middle of the - * 'bvec' because of bio splitting, so offset from the bvec - * must be passed to iov iterator - */ - offset = bio->bi_iter.bi_bvec_done; - bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter); + cmd->bvec = NULL; } - atomic_set(&cmd->ref, 2); - - iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq)); - iter.iov_offset = offset; cmd->iocb.ki_pos = pos; - cmd->iocb.ki_filp = file; + cmd->iocb.ki_filp = lo->lo_backing_file; cmd->iocb.ki_ioprio = req_get_ioprio(rq); if (cmd->use_aio) { cmd->iocb.ki_complete = lo_rw_aio_complete; @@ -398,6 +402,35 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, cmd->iocb.ki_complete = NULL; cmd->iocb.ki_flags = 0; } + return 0; +} + +static int lo_submit_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, + int nr_bvec, int rw) +{ + struct request *rq = blk_mq_rq_from_pdu(cmd); + struct file *file = lo->lo_backing_file; + struct iov_iter iter; + int ret; + + if (cmd->bvec) { + iov_iter_bvec(&iter, rw, cmd->bvec, nr_bvec, blk_rq_bytes(rq)); + iter.iov_offset = 0; + } else { + struct bio *bio = rq->bio; + struct bio_vec *bvec = __bvec_iter_bvec(bio->bi_io_vec, + bio->bi_iter); + + /* + * Same here, this bio may be started from the middle of the + * 'bvec' because of bio splitting, so offset from the bvec + * must be passed to iov iterator + */ + iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq)); + iter.iov_offset = bio->bi_iter.bi_bvec_done; + } + atomic_set(&cmd->ref, 2); + if (rw == ITER_SOURCE) { kiocb_start_write(&cmd->iocb); @@ -406,12 +439,84 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, ret = file->f_op->read_iter(&cmd->iocb, &iter); lo_rw_aio_do_completion(cmd); + return ret; +} + +static bool lo_backfile_support_nowait(const struct loop_device *lo) +{ + return lo->lo_backing_file->f_mode & FMODE_NOWAIT; +} +static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, + loff_t pos, int rw) +{ + int nr_bvec = lo_cmd_nr_bvec(cmd); + int ret; + + /* prepared already if we have tried nowait */ + if (!cmd->use_aio || !lo_backfile_support_nowait(lo)) { + ret = lo_rw_aio_prep(lo, cmd, nr_bvec, pos); + if (unlikely(ret)) + goto fail; + } + + cmd->iocb.ki_flags &= ~IOCB_NOWAIT; + ret = lo_submit_rw_aio(lo, cmd, nr_bvec, rw); +fail: if (ret != -EIOCBQUEUED) lo_rw_aio_complete(&cmd->iocb, ret); return -EIOCBQUEUED; } +static inline bool lo_aio_try_nowait(struct loop_device *lo, + struct loop_cmd *cmd) +{ + struct file *file = lo->lo_backing_file; + struct inode *inode = file->f_mapping->host; + struct request *rq = blk_mq_rq_from_pdu(cmd); + + /* NOWAIT works fine for backing block device */ + if (S_ISBLK(inode->i_mode)) + return true; + + /* + * NOWAIT is supposed to be fine for READ without contending with + * blocking WRITE + */ + if (req_op(rq) == REQ_OP_READ) + return true; + + /* + * If there is any queued non-NOWAIT async WRITE , don't try new + * NOWAIT WRITE for avoiding contention + * + * Here we focus on handling stable FS block mapping via NOWAIT + */ + return READ_ONCE(lo->lo_nr_blocking_writes) == 0; +} + +static int lo_rw_aio_nowait(struct loop_device *lo, struct loop_cmd *cmd, + int rw) +{ + struct request *rq = blk_mq_rq_from_pdu(cmd); + loff_t pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset; + int nr_bvec = lo_cmd_nr_bvec(cmd); + int ret = lo_rw_aio_prep(lo, cmd, nr_bvec, pos); + + if (unlikely(ret)) + goto fail; + + if (!lo_aio_try_nowait(lo, cmd)) + return -EAGAIN; + + cmd->iocb.ki_flags |= IOCB_NOWAIT; + ret = lo_submit_rw_aio(lo, cmd, nr_bvec, rw); +fail: + if (ret != -EIOCBQUEUED && ret != -EAGAIN) + lo_rw_aio_complete(&cmd->iocb, ret); + return ret; +} + static int do_req_filebacked(struct loop_device *lo, struct request *rq) { struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq); @@ -706,12 +811,19 @@ static ssize_t loop_attr_dio_show(struct loop_device *lo, char *buf) return sysfs_emit(buf, "%s\n", dio ? "1" : "0"); } +static ssize_t loop_attr_nr_blocking_writes_show(struct loop_device *lo, + char *buf) +{ + return sysfs_emit(buf, "%u\n", lo->lo_nr_blocking_writes); +} + LOOP_ATTR_RO(backing_file); LOOP_ATTR_RO(offset); LOOP_ATTR_RO(sizelimit); LOOP_ATTR_RO(autoclear); LOOP_ATTR_RO(partscan); LOOP_ATTR_RO(dio); +LOOP_ATTR_RO(nr_blocking_writes); static struct attribute *loop_attrs[] = { &loop_attr_backing_file.attr, @@ -720,6 +832,7 @@ static struct attribute *loop_attrs[] = { &loop_attr_autoclear.attr, &loop_attr_partscan.attr, &loop_attr_dio.attr, + &loop_attr_nr_blocking_writes.attr, NULL, }; @@ -795,13 +908,48 @@ static inline int queue_on_root_worker(struct cgroup_subsys_state *css) } #endif +static inline void loop_inc_blocking_writes(struct loop_device *lo, + struct loop_cmd *cmd) +{ + lockdep_assert_held(&lo->lo_work_lock); + + if (req_op(blk_mq_rq_from_pdu(cmd)) == REQ_OP_WRITE) + lo->lo_nr_blocking_writes += 1; +} + +static inline void loop_dec_blocking_writes(struct loop_device *lo, + struct loop_cmd *cmd) +{ + lockdep_assert_held(&lo->lo_work_lock); + + if (req_op(blk_mq_rq_from_pdu(cmd)) == REQ_OP_WRITE) + lo->lo_nr_blocking_writes -= 1; +} + static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd) { + struct request __maybe_unused *rq = blk_mq_rq_from_pdu(cmd); struct rb_node **node, *parent = NULL; struct loop_worker *cur_worker, *worker = NULL; struct work_struct *work; struct list_head *cmd_list; + /* always use the first bio's css */ + cmd->blkcg_css = NULL; + cmd->memcg_css = NULL; +#ifdef CONFIG_BLK_CGROUP + if (rq->bio) { + cmd->blkcg_css = bio_blkcg_css(rq->bio); +#ifdef CONFIG_MEMCG + if (cmd->blkcg_css) { + cmd->memcg_css = + cgroup_get_e_css(cmd->blkcg_css->cgroup, + &memory_cgrp_subsys); + } +#endif + } +#endif + spin_lock_irq(&lo->lo_work_lock); if (queue_on_root_worker(cmd->blkcg_css)) @@ -860,6 +1008,8 @@ queue_work: work = &lo->rootcg_work; cmd_list = &lo->rootcg_cmd_list; } + if (cmd->use_aio) + loop_inc_blocking_writes(lo, cmd); list_add_tail(&cmd->list_entry, cmd_list); queue_work(lo->workqueue, work); spin_unlock_irq(&lo->lo_work_lock); @@ -1856,6 +2006,7 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *rq = bd->rq; struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq); struct loop_device *lo = rq->q->queuedata; + int rw = 0; blk_mq_start_request(rq); @@ -1868,26 +2019,27 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx, case REQ_OP_WRITE_ZEROES: cmd->use_aio = false; break; - default: + case REQ_OP_READ: + rw = ITER_DEST; + cmd->use_aio = lo->lo_flags & LO_FLAGS_DIRECT_IO; + break; + case REQ_OP_WRITE: + rw = ITER_SOURCE; cmd->use_aio = lo->lo_flags & LO_FLAGS_DIRECT_IO; break; + default: + return BLK_STS_IOERR; } - /* always use the first bio's css */ - cmd->blkcg_css = NULL; - cmd->memcg_css = NULL; -#ifdef CONFIG_BLK_CGROUP - if (rq->bio) { - cmd->blkcg_css = bio_blkcg_css(rq->bio); -#ifdef CONFIG_MEMCG - if (cmd->blkcg_css) { - cmd->memcg_css = - cgroup_get_e_css(cmd->blkcg_css->cgroup, - &memory_cgrp_subsys); - } -#endif + /* try NOWAIT if the backing file supports the mode */ + if (cmd->use_aio && lo_backfile_support_nowait(lo)) { + int res = lo_rw_aio_nowait(lo, cmd, rw); + + if (res != -EAGAIN && res != -EOPNOTSUPP) + return BLK_STS_OK; + /* fallback to workqueue for handling aio */ } -#endif + loop_queue_work(lo, cmd); return BLK_STS_OK; @@ -1959,6 +2111,8 @@ static void loop_process_work(struct loop_worker *worker, cond_resched(); spin_lock_irq(&lo->lo_work_lock); + if (cmd->use_aio) + loop_dec_blocking_writes(lo, cmd); } /* @@ -2037,7 +2191,8 @@ static int loop_add(int i) lo->tag_set.queue_depth = hw_queue_depth; lo->tag_set.numa_node = NUMA_NO_NODE; lo->tag_set.cmd_size = sizeof(struct loop_cmd); - lo->tag_set.flags = BLK_MQ_F_STACKING | BLK_MQ_F_NO_SCHED_BY_DEFAULT; + lo->tag_set.flags = BLK_MQ_F_STACKING | BLK_MQ_F_NO_SCHED_BY_DEFAULT | + BLK_MQ_F_BLOCKING; lo->tag_set.driver_data = lo; err = blk_mq_alloc_tag_set(&lo->tag_set); |