[SCSI] Convert SCSI mid-layer to scsi_execute_async

Add scsi helpers to create really-large-requests and convert
scsi-ml to scsi_execute_async().

Per Jens's previous comments, I placed this function in scsi_lib.c.
I made it follow all the queue's limits - I think I did at least :), so
I removed the warning on the function header.

I think the scsi_execute_* functions should eventually take a request_queue
and be placed some place where the dm-multipath hw_handler can use them
if that failover code is going to stay in the kernel. That conversion
patch will be sent in another mail though.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 196 insertions, 34 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 1f2782767ca9..eb0cfbfbcf8f 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -63,39 +63,6 @@ static struct scsi_host_sg_pool scsi_sg_pools[] = {
 };      
 #undef SP
 
-
-/*
- * Function:    scsi_insert_special_req()
- *
- * Purpose:     Insert pre-formed request into request queue.
- *
- * Arguments:   sreq    - request that is ready to be queued.
- *              at_head - boolean.  True if we should insert at head
- *                        of queue, false if we should insert at tail.
- *
- * Lock status: Assumed that lock is not held upon entry.
- *
- * Returns:     Nothing
- *
- * Notes:       This function is called from character device and from
- *              ioctl types of functions where the caller knows exactly
- *              what SCSI command needs to be issued.   The idea is that
- *              we merely inject the command into the queue (at the head
- *              for now), and then call the queue request function to actually
- *              process it.
- */
-int scsi_insert_special_req(struct scsi_request *sreq, int at_head)
-{
-        /*
-         * Because users of this function are apt to reuse requests with no
-         * modification, we have to sanitise the request flags here
-         */
-        sreq->sr_request->flags &= ~REQ_DONTPREP;
-        blk_insert_request(sreq->sr_device->request_queue, sreq->sr_request,
-                           at_head, sreq);
-        return 0;
-}
-
 static void scsi_run_queue(struct request_queue *q);
 
 /*
@@ -249,8 +216,13 @@ void scsi_do_req(struct scsi_request *sreq, const void *cmnd,
 
         /*
          * head injection *required* here otherwise quiesce won't work
+         *
+         * Because users of this function are apt to reuse requests with no
+         * modification, we have to sanitise the request flags here
          */
-        scsi_insert_special_req(sreq, 1);
+        sreq->sr_request->flags &= ~REQ_DONTPREP;
+        blk_insert_request(sreq->sr_device->request_queue, sreq->sr_request,
+                           1, sreq);
 }
 EXPORT_SYMBOL(scsi_do_req);
 
@@ -327,6 +299,196 @@ int scsi_execute_req(struct scsi_device *sdev, const unsigned char *cmd,
 }
 EXPORT_SYMBOL(scsi_execute_req);
 
+struct scsi_io_context {
+        void *data;
+        void (*done)(void *data, char *sense, int result, int resid);
+        char sense[SCSI_SENSE_BUFFERSIZE];
+};
+
+static void scsi_end_async(struct request *req)
+{
+        struct scsi_io_context *sioc = req->end_io_data;
+
+        if (sioc->done)
+                sioc->done(sioc->data, sioc->sense, req->errors, req->data_len);
+
+        kfree(sioc);
+        __blk_put_request(req->q, req);
+}
+
+static int scsi_merge_bio(struct request *rq, struct bio *bio)
+{
+        struct request_queue *q = rq->q;
+
+        bio->bi_flags &= ~(1 << BIO_SEG_VALID);
+        if (rq_data_dir(rq) == WRITE)
+                bio->bi_rw |= (1 << BIO_RW);
+        blk_queue_bounce(q, &bio);
+
+        if (!rq->bio)
+                blk_rq_bio_prep(q, rq, bio);
+        else if (!q->back_merge_fn(q, rq, bio))
+                return -EINVAL;
+        else {
+                rq->biotail->bi_next = bio;
+                rq->biotail = bio;
+                rq->hard_nr_sectors += bio_sectors(bio);
+                rq->nr_sectors = rq->hard_nr_sectors;
+        }
+
+        return 0;
+}
+
+static int scsi_bi_endio(struct bio *bio, unsigned int bytes_done, int error)
+{
+        if (bio->bi_size)
+                return 1;
+
+        bio_put(bio);
+        return 0;
+}
+
+/**
+ * scsi_req_map_sg - map a scatterlist into a request
+ * @rq:         request to fill
+ * @sg:         scatterlist
+ * @nsegs:      number of elements
+ * @bufflen:    len of buffer
+ * @gfp:        memory allocation flags
+ *
+ * scsi_req_map_sg maps a scatterlist into a request so that the
+ * request can be sent to the block layer. We do not trust the scatterlist
+ * sent to use, as some ULDs use that struct to only organize the pages.
+ */
+static int scsi_req_map_sg(struct request *rq, struct scatterlist *sgl,
+                           int nsegs, unsigned bufflen, gfp_t gfp)
+{
+        struct request_queue *q = rq->q;
+        int nr_pages = (bufflen + PAGE_SIZE - 1) >> PAGE_SHIFT;
+        unsigned int data_len = 0, len, bytes, off;
+        struct page *page;
+        struct bio *bio = NULL;
+        int i, err, nr_vecs = 0;
+
+        for (i = 0; i < nsegs; i++) {
+                page = sgl[i].page;
+                off = sgl[i].offset;
+                len = sgl[i].length;
+                data_len += len;
+
+                while (len > 0) {
+                        bytes = min_t(unsigned int, len, PAGE_SIZE - off);
+
+                        if (!bio) {
+                                nr_vecs = min_t(int, BIO_MAX_PAGES, nr_pages);
+                                nr_pages -= nr_vecs;
+
+                                bio = bio_alloc(gfp, nr_vecs);
+                                if (!bio) {
+                                        err = -ENOMEM;
+                                        goto free_bios;
+                                }
+                                bio->bi_end_io = scsi_bi_endio;
+                        }
+
+                        if (bio_add_pc_page(q, bio, page, bytes, off) !=
+                            bytes) {
+                                bio_put(bio);
+                                err = -EINVAL;
+                                goto free_bios;
+                        }
+
+                        if (bio->bi_vcnt >= nr_vecs) {
+                                err = scsi_merge_bio(rq, bio);
+                                if (err) {
+                                        bio_endio(bio, bio->bi_size, 0);
+                                        goto free_bios;
+                                }
+                                bio = NULL;
+                        }
+
+                        page++;
+                        len -= bytes;
+                        off = 0;
+                }
+        }
+
+        rq->buffer = rq->data = NULL;
+        rq->data_len = data_len;
+        return 0;
+
+free_bios:
+        while ((bio = rq->bio) != NULL) {
+                rq->bio = bio->bi_next;
+                /*
+                 * call endio instead of bio_put incase it was bounced
+                 */
+                bio_endio(bio, bio->bi_size, 0);
+        }
+
+        return err;
+}
+
+/**
+ * scsi_execute_async - insert request
+ * @sdev:       scsi device
+ * @cmd:        scsi command
+ * @data_direction: data direction
+ * @buffer:     data buffer (this can be a kernel buffer or scatterlist)
+ * @bufflen:    len of buffer
+ * @use_sg:     if buffer is a scatterlist this is the number of elements
+ * @timeout:    request timeout in seconds
+ * @retries:    number of times to retry request
+ * @flags:      or into request flags
+ **/
+int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
+                       int data_direction, void *buffer, unsigned bufflen,
+                       int use_sg, int timeout, int retries, void *privdata,
+                       void (*done)(void *, char *, int, int), gfp_t gfp)
+{
+        struct request *req;
+        struct scsi_io_context *sioc;
+        int err = 0;
+        int write = (data_direction == DMA_TO_DEVICE);
+
+        sioc = kzalloc(sizeof(*sioc), gfp);
+        if (!sioc)
+                return DRIVER_ERROR << 24;
+
+        req = blk_get_request(sdev->request_queue, write, gfp);
+        if (!req)
+                goto free_sense;
+
+        if (use_sg)
+                err = scsi_req_map_sg(req, buffer, use_sg, bufflen, gfp);
+        else if (bufflen)
+                err = blk_rq_map_kern(req->q, req, buffer, bufflen, gfp);
+
+        if (err)
+                goto free_req;
+
+        req->cmd_len = COMMAND_SIZE(cmd[0]);
+        memcpy(req->cmd, cmd, req->cmd_len);
+        req->sense = sioc->sense;
+        req->sense_len = 0;
+        req->timeout = timeout;
+        req->flags |= REQ_BLOCK_PC | REQ_QUIET;
+        req->end_io_data = sioc;
+
+        sioc->data = privdata;
+        sioc->done = done;
+
+        blk_execute_rq_nowait(req->q, NULL, req, 1, scsi_end_async);
+        return 0;
+
+free_req:
+        blk_put_request(req);
+free_sense:
+        kfree(sioc);
+        return DRIVER_ERROR << 24;
+}
+EXPORT_SYMBOL_GPL(scsi_execute_async);
+
 /*
  * Function:    scsi_init_cmd_errh()
  *