block: add bsg helper library

This moves the FC classes bsg code to the block layer and
makes it a lib so that other classes like iscsi and SAS can use it.

It is helpful because working with the request queue, bios,
creating scatterlists, etc are a pain that the LLD does not
have to worry about with normal IOs and should not have to
worry about for bsg requests.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

3 files changed, 308 insertions, 0 deletions

diff --git a/block/Kconfig b/block/Kconfig
index 60be1e0455da..e97934eececa 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -65,6 +65,16 @@ config BLK_DEV_BSG
 
           If unsure, say Y.
 
+config BLK_DEV_BSGLIB
+        bool "Block layer SG support v4 helper lib"
+        default n
+        select BLK_DEV_BSG
+        help
+          Subsystems will normally enable this if needed. Users will not
+          normally need to manually enable this.
+
+          If unsure, say N.
+
 config BLK_DEV_INTEGRITY
         bool "Block layer data integrity support"
         ---help---
diff --git a/block/Makefile b/block/Makefile
index 0fec4b3fab51..514c6e4f427a 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_BLOCK) := elevator.o blk-core.o blk-tag.o blk-sysfs.o \
                         blk-iopoll.o blk-lib.o ioctl.o genhd.o scsi_ioctl.o
 
 obj-$(CONFIG_BLK_DEV_BSG)       += bsg.o
+obj-$(CONFIG_BLK_DEV_BSGLIB)    += bsg-lib.o
 obj-$(CONFIG_BLK_CGROUP)        += blk-cgroup.o
 obj-$(CONFIG_BLK_DEV_THROTTLING)        += blk-throttle.o
 obj-$(CONFIG_IOSCHED_NOOP)      += noop-iosched.o
diff --git a/block/bsg-lib.c b/block/bsg-lib.c
new file mode 100644
index 000000000000..f8c0a61a529c
--- /dev/null
+++ b/block/bsg-lib.c
@@ -0,0 +1,297 @@
+/*
+ *  BSG helper library
+ *
+ *  Copyright (C) 2008   James Smart, Emulex Corporation
+ *  Copyright (C) 2011   Red Hat, Inc.  All rights reserved.
+ *  Copyright (C) 2011   Mike Christie
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ */
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/delay.h>
+#include <linux/scatterlist.h>
+#include <linux/bsg-lib.h>
+#include <scsi/scsi_cmnd.h>
+
+/**
+ * bsg_destroy_job - routine to teardown/delete a bsg job
+ * @job: bsg_job that is to be torn down
+ */
+static void bsg_destroy_job(struct bsg_job *job)
+{
+        put_device(job->dev);   /* release reference for the request */
+
+        kfree(job->request_payload.sg_list);
+        kfree(job->reply_payload.sg_list);
+        kfree(job);
+}
+
+/**
+ * bsg_job_done - completion routine for bsg requests
+ * @job: bsg_job that is complete
+ * @result: job reply result
+ * @reply_payload_rcv_len: length of payload recvd
+ *
+ * The LLD should call this when the bsg job has completed.
+ */
+void bsg_job_done(struct bsg_job *job, int result,
+                  unsigned int reply_payload_rcv_len)
+{
+        struct request *req = job->req;
+        struct request *rsp = req->next_rq;
+        int err;
+
+        err = job->req->errors = result;
+        if (err < 0)
+                /* we're only returning the result field in the reply */
+                job->req->sense_len = sizeof(u32);
+        else
+                job->req->sense_len = job->reply_len;
+        /* we assume all request payload was transferred, residual == 0 */
+        req->resid_len = 0;
+
+        if (rsp) {
+                WARN_ON(reply_payload_rcv_len > rsp->resid_len);
+
+                /* set reply (bidi) residual */
+                rsp->resid_len -= min(reply_payload_rcv_len, rsp->resid_len);
+        }
+        blk_complete_request(req);
+}
+EXPORT_SYMBOL_GPL(bsg_job_done);
+
+/**
+ * bsg_softirq_done - softirq done routine for destroying the bsg requests
+ * @rq: BSG request that holds the job to be destroyed
+ */
+static void bsg_softirq_done(struct request *rq)
+{
+        struct bsg_job *job = rq->special;
+
+        blk_end_request_all(rq, rq->errors);
+        bsg_destroy_job(job);
+}
+
+static int bsg_map_buffer(struct bsg_buffer *buf, struct request *req)
+{
+        size_t sz = (sizeof(struct scatterlist) * req->nr_phys_segments);
+
+        BUG_ON(!req->nr_phys_segments);
+
+        buf->sg_list = kzalloc(sz, GFP_KERNEL);
+        if (!buf->sg_list)
+                return -ENOMEM;
+        sg_init_table(buf->sg_list, req->nr_phys_segments);
+        buf->sg_cnt = blk_rq_map_sg(req->q, req, buf->sg_list);
+        buf->payload_len = blk_rq_bytes(req);
+        return 0;
+}
+
+/**
+ * bsg_create_job - create the bsg_job structure for the bsg request
+ * @dev: device that is being sent the bsg request
+ * @req: BSG request that needs a job structure
+ */
+static int bsg_create_job(struct device *dev, struct request *req)
+{
+        struct request *rsp = req->next_rq;
+        struct request_queue *q = req->q;
+        struct bsg_job *job;
+        int ret;
+
+        BUG_ON(req->special);
+
+        job = kzalloc(sizeof(struct bsg_job) + q->bsg_job_size, GFP_KERNEL);
+        if (!job)
+                return -ENOMEM;
+
+        req->special = job;
+        job->req = req;
+        if (q->bsg_job_size)
+                job->dd_data = (void *)&job[1];
+        job->request = req->cmd;
+        job->request_len = req->cmd_len;
+        job->reply = req->sense;
+        job->reply_len = SCSI_SENSE_BUFFERSIZE; /* Size of sense buffer
+                                                 * allocated */
+        if (req->bio) {
+                ret = bsg_map_buffer(&job->request_payload, req);
+                if (ret)
+                        goto failjob_rls_job;
+        }
+        if (rsp && rsp->bio) {
+                ret = bsg_map_buffer(&job->reply_payload, rsp);
+                if (ret)
+                        goto failjob_rls_rqst_payload;
+        }
+        job->dev = dev;
+        /* take a reference for the request */
+        get_device(job->dev);
+        return 0;
+
+failjob_rls_rqst_payload:
+        kfree(job->request_payload.sg_list);
+failjob_rls_job:
+        kfree(job);
+        return -ENOMEM;
+}
+
+/*
+ * bsg_goose_queue - restart queue in case it was stopped
+ * @q: request q to be restarted
+ */
+void bsg_goose_queue(struct request_queue *q)
+{
+        if (!q)
+                return;
+
+        blk_run_queue_async(q);
+}
+EXPORT_SYMBOL_GPL(bsg_goose_queue);
+
+/**
+ * bsg_request_fn - generic handler for bsg requests
+ * @q: request queue to manage
+ *
+ * On error the create_bsg_job function should return a -Exyz error value
+ * that will be set to the req->errors.
+ *
+ * Drivers/subsys should pass this to the queue init function.
+ */
+void bsg_request_fn(struct request_queue *q)
+{
+        struct device *dev = q->queuedata;
+        struct request *req;
+        struct bsg_job *job;
+        int ret;
+
+        if (!get_device(dev))
+                return;
+
+        while (1) {
+                req = blk_fetch_request(q);
+                if (!req)
+                        break;
+                spin_unlock_irq(q->queue_lock);
+
+                ret = bsg_create_job(dev, req);
+                if (ret) {
+                        req->errors = ret;
+                        blk_end_request_all(req, ret);
+                        spin_lock_irq(q->queue_lock);
+                        continue;
+                }
+
+                job = req->special;
+                ret = q->bsg_job_fn(job);
+                spin_lock_irq(q->queue_lock);
+                if (ret)
+                        break;
+        }
+
+        spin_unlock_irq(q->queue_lock);
+        put_device(dev);
+        spin_lock_irq(q->queue_lock);
+}
+EXPORT_SYMBOL_GPL(bsg_request_fn);
+
+/**
+ * bsg_setup_queue - Create and add the bsg hooks so we can receive requests
+ * @dev: device to attach bsg device to
+ * @q: request queue setup by caller
+ * @name: device to give bsg device
+ * @job_fn: bsg job handler
+ * @dd_job_size: size of LLD data needed for each job
+ *
+ * The caller should have setup the reuqest queue with bsg_request_fn
+ * as the request_fn.
+ */
+int bsg_setup_queue(struct device *dev, struct request_queue *q,
+                    char *name, bsg_job_fn *job_fn, int dd_job_size)
+{
+        int ret;
+
+        q->queuedata = dev;
+        q->bsg_job_size = dd_job_size;
+        q->bsg_job_fn = job_fn;
+        queue_flag_set_unlocked(QUEUE_FLAG_BIDI, q);
+        blk_queue_softirq_done(q, bsg_softirq_done);
+        blk_queue_rq_timeout(q, BLK_DEFAULT_SG_TIMEOUT);
+
+        ret = bsg_register_queue(q, dev, name, NULL);
+        if (ret) {
+                printk(KERN_ERR "%s: bsg interface failed to "
+                       "initialize - register queue\n", dev->kobj.name);
+                return ret;
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(bsg_setup_queue);
+
+/**
+ * bsg_remove_queue - Deletes the bsg dev from the q
+ * @q:  the request_queue that is to be torn down.
+ *
+ * Notes:
+ *   Before unregistering the queue empty any requests that are blocked
+ */
+void bsg_remove_queue(struct request_queue *q)
+{
+        struct request *req; /* block request */
+        int counts; /* totals for request_list count and starved */
+
+        if (!q)
+                return;
+
+        /* Stop taking in new requests */
+        spin_lock_irq(q->queue_lock);
+        blk_stop_queue(q);
+
+        /* drain all requests in the queue */
+        while (1) {
+                /* need the lock to fetch a request
+                 * this may fetch the same reqeust as the previous pass
+                 */
+                req = blk_fetch_request(q);
+                /* save requests in use and starved */
+                counts = q->rq.count[0] + q->rq.count[1] +
+                         q->rq.starved[0] + q->rq.starved[1];
+                spin_unlock_irq(q->queue_lock);
+                /* any requests still outstanding? */
+                if (counts == 0)
+                        break;
+
+                /* This may be the same req as the previous iteration,
+                 * always send the blk_end_request_all after a prefetch.
+                 * It is not okay to not end the request because the
+                 * prefetch started the request.
+                 */
+                if (req) {
+                        /* return -ENXIO to indicate that this queue is
+                         * going away
+                         */
+                        req->errors = -ENXIO;
+                        blk_end_request_all(req, -ENXIO);
+                }
+
+                msleep(200); /* allow bsg to possibly finish */
+                spin_lock_irq(q->queue_lock);
+        }
+        bsg_unregister_queue(q);
+}
+EXPORT_SYMBOL_GPL(bsg_remove_queue);